TABLE D-1 Toluene Exposure as a Risk Factor for Noise-Induced Hearing Loss
Citation |
Design |
Population |
Exposures and Source of Exposure Data |
a. Human Studies |
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Schaper et al. (2003) |
Longitudinal study, 1996–2001 |
192 employees from 14 German rotogravure printing plants with 4 examinations Subjects at each examination: Exam 1:333 Exam 2:278 Exam 3:241 Exam 4:216 Stratification Toluene exposure: low vs high (based on worksite) Job tenure: short vs long Noise exposure: low (< 82 dBA) vs high (≥82 dBA) |
Medical, psychological examinations Toluene and noise exposure measured 2 times per yr for each subject Historical records for past exposure estimates Toluene: Mean study exposure: High: 26 ppm Low: 3 ppm Lifetime weighted average daily exposure (for current exposure groups) High: 45 ppm Low: 10 ppm Biomarkers of exposure: hippuric acid, o-cresol Noise: lifetime average daily exposure Current high noise: 82 dBA Current low noise: 81 dBA |
Morata et al. (1997) |
Cross-sectional |
124 male rotogravure printing workers, Sao Paulo, Brazil Mean age: 34 yrs (range 21–58 yrs) Employed at least 1 yr Mean tenure: 7 yrs (range 1–25 yrs) |
Solvent exposure: TWA exposure evaluation for toluene, ethanol, and ethyl acetate Toluene levels (air): 0.14 to 919 mg/m 3 109 workers monitored for hippuric acid and creatinine in their urine Noise exposure: Continuous noise, 71 to 93 dBA; dosimetry for individual workers |
Outcome Measure |
Results |
Comments |
Hearing thresholds Hearing loss: thresholds > 25 dB Tested at 0.125–12 kHz Age adjustment based on ISO 7029 (1984) before repeated measures analysis |
No sig effect on auditory thresholds for toluene intensity, exposure duration, or interactions Sig effect of current noise intensity (F = 4.5, p = .04) |
Subjects were volunteers; some loss to follow-up No unexposed control group Little difference in noise exposure for high and low toluene exposure |
High-freq hearing loss: notch in a freq b/t 3 and 6 kHz or thresholds poorest in this freq range Normal hearing: no single threshold > 25 dB Pure-tone audiometry: 0.5–8 kHz |
No statistical interactions between noise and toluene Concentration of toluene in air was not sig associated w/ hearing loss Level of biological marker for toluene exposure (urinary hippuric acid) sig associated w/ hearing loss (OR = 1.76, 95% CI 1.00–2.98) |
93% of subjects reported no exposure to major sources of nonoccupational noise (e.g., firearms, motorcycles, etc.) 11% of those exposed to noise > 85 dBA used hearing protection |
Citation |
Design |
Population |
Exposures and Source of Exposure Data |
Morata et al. (1993) |
Cross-sectional |
190 male printing and paint manufacturing workers, Brazil Employed at least 1 yr Mean employment: Printing: 8 to 13 yrs Paint mfg: 6 yrs Exposure groups Noise only (printing): 50 Noise and toluene (printing): 51 Mixed solvents, no excess noise (paint mfg): 39 Unexposed (printing): 50 |
Noise only group: 88–97 dBA (continuous); dose 209–335% (5-dB exchange rate) Noise and toluene group: 88–98 dBA; dose 140–350% (5-dB exchange rate); toluene TWA 75–600 ppm Mixed solvents group: no dose data; toluene concentration 10–70 ppm (11 samples) Interviewed for work, exposure, and medical histories |
b. Animal Studies |
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Davis et al. (2002) |
Experimental |
33 chinchillas, in 6 exposure groups 6 adult rats as control group |
10-day exposures Toluene: 2000 ppm Noise: 500 Hz octave band noise, 97.5 dB SPL Background noise < 60 dBA 22 chinchillas (monaural) Group 1:8 h toluene, background noise only Group 2: no toluene, 8 h noise Group 3:8 h toluene, 8 h noise Group 4: control group |
Outcome Measure |
Results |
Comments |
Normal hearing Worst threshold at 3–8 kHz (avg left and right ears): 0–25 dB; average of 0.5, 1, 2 kHz ≤ 25 dB High-freq hearing loss Categories based on worst threshold at 3–8 kHz (avg left and right ears) and average of 0.5, 1, 2 kHz ≤ 25 dB: (I) 30–40 dB, (II) 45–55 dB, (III) ≥ 60 dB (IV) average of 0.5, 1, 2 kHz > 25 dB Other hearing loss Unilateral, conductive Pure-tone audiometry: 0.5–8 kHz Otoscopy, immittance audiometry |
Prevalence of high-freq hearing loss: 8% unexposed 26% noise 53% noise and toluene 18% mixture of solvents Relative risk of high-freq hearing loss: Noise only: 4.1 (95% CI 1.4–12.2) Noise and toluene: 10.9 (95% CI 4.1–28.9) Solvents only: 5.0 (95% CI 1.5–17.5) |
Noise and solvent exposures in the different groups were not equivalent Without a group exposed to only toluene, could not assess whether effect of combined exposure was additive or multiplicative |
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Differences in liver metabolism of toluene suggest that rats and mice are better models for human ototoxicity than chinchillas |
Chinchillas ABR threshold shifts (pre- vs postexposure) Tested at 0.5, 1, 2, 4, 8, 16 kHz Postexposure testing on days 1, 3, 7, 14, and 30 |
Chinchillas Noise effects, but no ototoxicity Noise: 12 dB permanent threshold shift at 2 and 4 kHz Analysis of variance: no sig main effect for toluene alone or interaction of toluene w/ noise |
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Citation |
Design |
Population |
Exposures and Source of Exposure Data |
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11 chinchillas (binaural) Group 5:12 h toluene, 8 h noise; noise from 2 h after start to 2 h before end of toluene exposure Group 6:12 h toluene, background noise only Rat comparison group 6 adult rats exposed to toluene at 2000 ppm, 8 h / day for 5 days Only background noise |
Johnson et al. (1990) |
Experimental |
49 young male rats Exposure groups: Controls: 10 Noise: 10 Toluene: 10 Noise followed by toluene: 10 Noise, rest, toluene: 9 |
Toluene: 1000 ppm, 16 h/d, 7 d/w (11:00 am to 3:00 am) Noise: 10 h/d, 7 d/w Continuously varying signal: 2 kHz wide noise band, sweeping from 3 to 30 kHz at freq of 0.5 Hz Equivalent to sound level of 100 dB Controls: no noise or toluene Noise: 4 wks Toluene: 2 wks Noise followed by toluene: 4 wks noise, 2 wks toluene Noise, rest, toluene: 4 wks noise, 4 wks rest, 2 wks toluene |
Outcome Measure |
Results |
Comments |
Rats ABR threshold shifts (pre- vs postexposure) Tested at 8, 16, 32 kHz Postexposure testing on day 30 |
Rats Sig permanent threshold shift w/ shorter toluene exposure Threshold shifts of 20 and 15 dB at 16 and 32 kHz, respectively |
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ABR thresholds at 1.6, 3.15, 6.3, 12.5, 20.0 kHz Measured at 1–5 wks after termination of exposure |
Effect of noise followed by toluene, w/ or w/o rest, was larger than exposure to noise or toluene alone at 6.3, 12.5, and 20.0 kHz Noise: higher thresholds than controls at 6.3 (9 dB, p < .05), 12.5 (26 dB, p < .001), and 20.0 kHz (18 dB, p < .001) Toluene: higher thresholds than controls at all freq (1.6 to 12.5 kHz, 15–32 dB, p < .001; 20.0 kHz, 15 dB, p < .01) Noise followed by toluene: higher thresholds than controls at all freq (1.6 kHz, 8 dB, p < .05; 3.15 to 20.0 kHz, 34–45 dB, p < .001) |
Additive effects from noise and toluene Exposure to toluene after noise may produce smaller losses than exposure to noise after toluene |
Outcome Measure |
Results |
Comments |
ABR threshold shifts at 1.6, 3.15, 6.3, 12.5, 20.0 kHz Controls: at age 5 mos Group T: 2–5 days after termination of exposure; repeated 1 and 6 mos later Group N: 2–5 days after termination of exposure Group T+N: 2–5 days after termination of noise exposure, repeated 6 mos later |
Group T: Higher thresholds than controls at all freq (p < .001); greatest difference (40 dB) at 12.5 kHz; improvement at most frequencies at 1 mo (5–10 dB) and 6 mo (5 dB) Group N: Higher thresholds than controls; greatest difference at highest freqs (6.3, 12.5, and 20.0 kHz; p < .001); maximum difference (50 dB) at 12.5 kHz Group T+N: Higher thresholds than controls at all freq (p < .001); for most animals, threshold exceeded maximum stimulus intensity at 12.5 and 20.0 kHz For any exposure, threshold shift greatest at 6.3 and 12.5 kHz; after 6 mos, greatest at 12.5 kHz Combined exposure (toluene followed by noise) produced greater shifts at 3.15 (p < .01) and 6.3 kHz (p < .0001) than summed losses for single exposures |
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TABLE D-2 Carbon Monoxide as a Risk Factor for Noise-Induced Hearing Loss in Animals
Citation |
Design |
Population |
Exposures |
Rao and Fechter (2000) |
Experimental |
Rats |
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A: Combined exposure |
8 exposure groups: in each, n = 6 Random assignment |
CO: 1200 ppm Octave band noise w/ center frequency of 13.6 kHz (9.6–19.2 kHz) Background noise: ~ 50 dBA CO only Noise only: 95 dB for 4 h 100 dB for 2 h 105 dB for 1 hr Noise plus CO: 95 dB for 4 h, 100 dB for 2 h 105 dB for 1 hr Control: Air only |
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B: Increased duration of exposure |
2 exposure groups: in each, n = 6 |
CO: 1200 ppm Noise: 105 dB Noise only: 4 h Noise plus CO: 4 h |
Outcome Measure |
Results |
Comments |
CAP thresholds for 11 pure tones between 2 and 40 kHz 4-wk recovery period |
Exposure groups significantly different from each other (F(8, 45) = 13.04, p < .05) Sig interaction b/t freq and exposure (F(80, 450) = 4.35, p < .05) Potentiation of threshold elevation for combined exposure does not increase beyond 100 dB for 2h 95 dB for 4h Combined exposure: 6 dB threshold elevation above noise only; difference not sig at any frequency 100 dB for 2h Combined exposure: sig elevation over noise only at all frequencies (p < .05) 105 dB for 1h Combined exposure: sig elevation over noise only at all frequencies (p < .05); greater dysfunction at lower freq than w/ other exposures Noise only: sig elevation over thresholds for 95 dB (4h), 100 dB (2h) (p < .05) CO only No sig difference from exposure to air only F(1,10) = 1.72, p > .05 |
Rats more resistant to CO than humans (30 min LD50 = 5000 ppm for rats; 1500 ppm immediately dangerous for humans) |
CAP thresholds for 11 pure tones between 2 and 40 kHz 4-wk recovery period |
Combined exposure: threshold elevations not sig diff from noise only Combined exposure: threshold elevations 15 dB greater than for 105 dB + CO for 1h |
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Citation |
Design |
Population |
Exposures |
Fechter et al. (2000) |
Experimental |
Rate |
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A: Variation of CO dose |
8 exposure groups: in each, n = 8 Random assignment |
CO: varied exposures Noise: 100 dB octave band noise w/ center frequency of 13.6 kHz Background noise: < 35 dB CO only: 1200 ppm, 8 h Noise only: 8 h Noise plus CO (5 exposure groups): 8 h noise and CO at 300, 500, 700, 1200, or 1500 ppm Control: air only |
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B: Variation of noise dose |
8 exposure groups: in each, n = 6 Random assignment |
CO: 1200 ppm Noise: Octave band noise w/ center frequency of 13.6 kHz CO only: 4 h Noise only: 95 dB: 2 h 100 dB: 2 h 100 dB: 4 h Noise plus CO: 95 dB: 2 h 100 dB: 2 h 100 dB: 4 h Control: Air only |
Outcome Measure |
Results |
Comments |
CAP thresholds for 11 pure tones between 2 and 40 kHz 4-wk recovery period |
Noise plus CO Potentiation of noise effects by CO exposure emerges at CO exposures of 500 ppm and increases as CO level increases Sig elevation of thresholds over exposure to noise only with exposures to CO levels > 300 ppm Thresholds at lower frequencies affected only w/ CO levels ≥ 1200 ppm; CO only No effect on auditory function |
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CAP thresholds for 11 pure tones between 2 and 40 kHz 4-wk recovery period |
Nonlinear relationship b/t noise severity and potentiation of threshold elevation by CO Potentiation of noise effects by CO exposure greatest w/ noise exposure of 100 dB for 2 h For noise exposure of 100 dB for 4 h, no additional effect at higher freq from CO exposure; sig differences at some lower freq Sig difference from controls for noise exposure of 100 dB for 2 or 4 h, w/ or w/o CO |
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Citation |
Design |
Population |
Exposures |
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C: Repeated exposures |
4 exposure groups: in each, n = 8 Random assignment |
CO level: 1200 ppm Noise exposure: Octave band noise w/ center frequency of 13.6 kHz Exposure duration: 5 successive days: CO only Noise only: 95 dB, 2 h Noise plus CO Control: Air only |
Chen and Fechter (1999) |
Experimental |
Rats |
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A: Response to CO and high-frequency vs low-frequency noise |
Exposure groups: High-freq noise CO: n = 4 Noise: n = 7 Noise plus CO: n = 7 Air: n = 7 Low-freq noise CO: n = 4 Noise: n = 4 Noise plus CO: n = 4 Air: n = 7 Random assignment |
CO level: 1200 ppm Noise exposure: 8h, octave band noise High freq: 9.6–19.2 kHz at 100 dB (Ln) Low freq: 2.4–4.8 kHz at 115 dB (Ln) |
Outcome Measure |
Results |
Comments |
CAP thresholds for 11 pure tones between 2 and 40 kHz 4-wk recovery period |
Sig elevation of thresholds for noise plus CO exposure compared with noise only No effect of repeated exposure to CO only |
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CAP and CM threshold shifts at freq from 2 to 40 kHz 4-wk recovery period |
High-freq noise Noise plus CO produced sig greater CAP threshold shifts than noise alone (p < .05); greater potentiation at higher freq Noise alone produced sig CAP threshold shifts from air alone at freq > 8 kHz CO alone produced no CAP threshold shifts from air alone CM elevations for noise and noise plus CO, at all freq, w/ greater elevations at high freq and for combined exposure Low-freq noise Noise plus CO produced sig greater threshold shifts than noise alone (p < .05); somewhat greater potentiation at low freq Noise alone produced sig CAP threshold shifts at all freq CO alone produced no CAP threshold shifts CM elevations for noise plus CO over noise alone at all freq, w/ greater differences at low freq; sig differences at only three freq |
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Citation |
Design |
Population |
Exposures |
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B: Response to CO w/ varied noise exposure |
Exposure groups: Noise Noise plus CO |
CO: 1200 ppm Noise: octave band noises at 100 dB (Ln) 9.6–19.2 kHz 4.8–9.6 kHz 2.4–4.8 kHz 1.2–2.4 kHz |
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C: Comparison of potentiation measured by CAP and CM |
Exposure groups: Noise Noise plus CO |
CO levels: 300, 500, 700, 1200, 1500 ppm High frequency noise: 9.6–19.2 kHz Low frequency noise: 2.4–4.8 kHz |
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D: Recovery of auditory thresholds over time |
Exposure groups for each recovery period: 1 wk Noise: n = 4 Noise plus CO: n = 3 4 wks Noise: n = 7 Noise plus CO: n = 7 Air: n = 7 |
CO level: 1200 ppm Noise: 9.6–19.2 kHz at 100 dB (Ln) |
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E: Hearing loss potentiation and CO concentration |
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CO level: 0–1500 ppm Noise: 8 h, 9.6–19.2 kHz at 100 dB (Ln) |
Outcome Measure |
Results |
Comments |
CAP and CM threshold shifts in three freq ranges: Low: 2–8 kHz Mid: 12–20 kHz High: 24–40 kHz |
Noise plus CO: CAP threshold shifts and CM elevations greater than noise alone, especially at high and mid frequencies, for 9.6–19.2 kHz and 4.8–9.6 kHz bands Noise alone: only 9.6–19.2 kHz noise band caused significant CAP threshold shifts and CM elevations |
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Difference in mean CAP or CM between noise plus CO and noise alone High-frequency noise: measured at freq > 8kHz Low-frequency noise: measured at 2–6 kHz |
Potentiations shown by CAP and CM are correlated and similar |
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CAP thresholds measured at 1 wk, 2 wks, and 4 wks after exposure |
Thresholds sig higher than controls for noise plus CO and noise alone at freq > 8 kHz Noise plus CO: No sig difference b/t 1 wk and 4 wks Noise alone: Lower thresholds at 4 wks than at 1 wk; sig differences at 12, 16, 30, 35 kHz; remain sig higher than controls at > 8 kHz |
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Average CAP thresholds measured at 2–8 kHz, 12–20 kHz, and 24–40 kHz 4-wk recovery period |
Greater potentiation with higher CO levels; CO effect varies across freq ranges Potentiation of hearing loss begins at CO level of 300–500 ppm for freq > 8 kHz |
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Outcome Measure |
Results |
Comments |
Reflex modulation audiometry: detection sensitivity thresholds at 10 and 40 kHz Thresholds measured before exposure and at 1 wk and 3 wks postexposure |
CO only: no evidence of worse auditory functioning after exposure Noise only: worse thresholds after exposure (p < .01); 10 kHz worse than 40 kHz at 1 wk Noise plus CO: thresholds worse than noise alone; greater shift at 40 kHz than 10 kHz; sig interaction effect at 1 week (p < .05); not sig at 3 wks Control: thresholds unchanged |
CO levels higher than those likely in occupational settings |
TABLE D-3 Smoking as a Risk Factor for Noise-Induced Hearing Loss
Citation |
Design |
Population |
Exposures and Source of Exposure Data |
Ferrite and Santana (2005) |
Cross-sectional |
535 male metal plant workers participating in hearing screening and enrolled in health promotion program Northeast Brazil Exclusions: women; age > 55 yrs; missing audiometric data; hearing loss inconsistent with noise damage |
Questionnaire: sociodemographics, lifestyle, occupational and health-related data, and smoking Noise exposure Based on job-noise matrix: Exposed: jobs w/ 81–93 dBA Nonexposed: jobs w/ < 81 dBA Pre-employment noise exposure assessed Total duration of exposure: 0 < 4 yrs and ≥ 4 yrs Smoking Nonsmokers (never smoked or < 6 months) Ever-smokers (current or past smokers) Age categories 20–40 yrs, 41–55 yrs |
Palmer et al. (2004) |
Cross-sectional |
12,907 men and women 10,418 with responses on hearing Britain, 1997–1998 Age: 16–64 yrs Postal survey of randomly selected members of armed forces and persons from age-sex registers of 163 general practitioners in Britain |
Survey questionnaire: exposure to vibration, time spent working in noisy jobs, smoking history, and hearing aid use Noise Time spent working in noisy places (a need to shout to be heard; considered equivalent to at least 85–90 dBA) Smoking history Smoker: smoked at least once/day for at least 1 month Current smokers Former smokers Lifelong nonsmokers |
Outcome Measure |
Results |
Comments |
Hearing loss: hearing threshold > 25 dB HL at 3, 4, 6, or 8 kHz Pure-tone hearing thresholds measured at 0.25, 0.5, 1, 2, 3, 4, 6, 8 kHz |
Smoking w/ noise exposure, was sig. associated w/ greater hearing loss compared w/ younger nonsmokers not exposed to noise Younger workers: PR = 4.85 (90% CI 2.49–9.46) Older workers: PR = 7.65 (90% CI 4.43–13.23) Smoking alone not sig associated with greater hearing loss in younger workers (PR = 1.27, 90% CI: 0.37–4.32) Prevalence of hearing loss: Older noise-exposed smokers: 46% Younger noise-exposed smokers: 29% Older nonsmokers not exposed to noise: 24% Younger nonsmokers not exposed to noise: 6% |
No other known ototoxic agents in the workplace Smoking, noise exposure, and age examined as dichotomous variables No information on use of hearing protection Possibility of selection bias from exclusion of workers without existing audiometric test data Nonoccupational noise exposure not considered |
Self-reported hearing difficulties assessed by response to— “How well can you hear a person who is talking to you when he is sitting on your right [left] side in a quiet room?” Severe difficulty in worse ear, or wore hearing aid Moderate difficulty in worse ear Normal: no or slight difficulty |
Combined exposure to noise and smoking was consistent with an additive effect Current vs nonsmokers with moderate to severe hearing difficulty No work noise: PR = 1.5 (95% CI 1.1–2.1) 1–5 yrs work in noise: PR = 3.3 (95% CI 2.4 to 4.5) > 5 yrs work in noise: PR = 5.7 (95% CI 4.4 to 7.1) (PRs age- and sex-adjusted) |
Response rate was 58%; response rate higher for women and older subjects No dose-response effect tested for smoking or noise Use of hearing protection not determined |
Citation |
Design |
Population |
Exposures and Source of Exposure Data |
Mizoue et al. (2003) |
Cross-sectional |
4,624 male steel company workers Japan, 1999 Age: < 61 yrs Current smokers: 56% Working in potentially high noise levels: 29% Exclusions: no auditory examination, incomplete smoking history, ex-smoker |
Noise exposure Company worksite records for workers who had hearing tests Worksite noise levels measured twice/yr Smoking history As reported at periodic audiometric tests Nonsmoker: never smoked Ex-smoker Current smoker Cigarettes per day: < 15, 15–24, ≥ 25 Age groups < 40, 40–49, 50–60 yrs |
Starck et al. (1999) |
Cross-sectional |
199 professional forest workers 171 shipyard workers Finland Mean age: Forest workers: 43 yrs Shipyard workers: 38 yrs Exclusions: hearing loss from ear diseases or severe head injuries |
Questions to establish work history and use of hearing protection, smoking history Medical records reviewed, overall health status, otological examination Noise exposure A-weighted noise level for average working day for both groups: 100 dB Effective exposure with hearing protectors (measured for each worker) Forest workers: 95 dB Shipyard workers: 85 dB Smoking Nonsmokers: never smoked or quit > 10 yrs ago Smokers |
Outcome Measure |
Results |
Comments |
Hearing loss (worse ear) Low frequency: pure-tone threshold > 25 dB HL at 1 kHz High frequency: pure-tone threshold > 40 dB HL at 4 kHz Pure-tone air conduction audiometric tests: Workers w/o significant noise exposure: 1, 4 kHz Workers in noisy environments (> 85 dBA): 0.5, 1, 2, 4, 8 kHz |
Combined effect of noise and smoking on high-frequency hearing loss is comparable to sum of their independent effects 4 kHz comparisons w/ nonsmokers not exposed to noise Smokers exposed to occ noise: PRR = 2.56 (95% CI 2.12 to 3.07) Smokers not exposed to noise: PRR = 1.57 (95% CI 1.31 to 1.89) Nonsmokers exposed to noise: PRR= 1.77 (95% CI 1.36 to 2.30) Smoking not associated with low-frequency hearing loss |
No control for past occupational noise exposure or leisure time noise exposure No information on ear disease or injuries that might have affected hearing PRR calculated by Cochran-Mantel-Haenszel method, w/ age stratification |
Hearing level at 4 kHz Measured hearing level compared with expected level (ISO-1999), calculated on the basis of age, noise level (A-wt), and duration of exposure (50% estimate) Age correction of hearing levels with ISO 1999 (1990) model |
Variation in hearing loss explained (linear regression) Forest workers Age: 26% Noise exposure: 10% Smoking: 1% (p=ns) Shipyard workers Age: 48% Noise exposure: 15% Smoking: 3% (p < .05) Hearing levels for smokers and nonsmokers not significantly different |
All workers exposed to noise; differed in noise levels and duration of exposure |
Citation |
Design |
Population |
Exposures and Source of Exposure Data |
Cruickshanks et al. (1998) |
Population-based, cross-sectional |
3,753 adults, ages 48–92 yrs Beaver Dam, Wisconsin, 1993–1995 Mean age: 66 yrs 58% women |
Questionnaire and examination Noise exposure History of occupational noise exposure: having to speak in a loud voice to be heard; farmer driving tractor w/o cab, or military service with noise (pilot, aircraft or tank crew, ship engine room, use of grenades, mortars, multiperson weapons systems) Smoking status at examination Nonsmoker: < 100 cigarettes (lifetime) Ex-smoker Current smoker Amount smoked Pack-years |
Virokannas and Anttonen (1995) |
Cross-sectional |
433 reindeer herders Northern Finland, 1988 Mean age: 43 yrs (range 18–64 yrs) Exclusions: accidental exposure to explosion; suffered ear disease; abnormal findings for tympanic membrane |
Clinical examination and questions on exposure to noise, smoking history, use of ear protectors Principal noise sources: Snowmobiles: 92–104 dBA Chainsaws: 96–103 dBA Gunshots: under 80 dBA (annual equivalent) Noise exposure (based on cumulative hrs of use of noisy tools and vehicles) Mild: 0–3,700 h Moderate: 3,701–8,700 h Heavy: 8,701–15,000 h |
Outcome Measure |
Results |
Comments |
Hearing loss: Average hearing threshold at 0.5, 1, 2, and 4 kHz > 25 dB HL (worse ear) Mild: > 25, ≤ 40 dB HL Moderate: > 40, ≤ 60 dB HL Marked: > 60 dB HL |
Current smokers had sig increased risk of hearing loss compared w/ nonsmokers among those w/ and w/o occupational noise exposure W/ occupational noise: OR = 1.85 (95% CI 1.33–2.57) W/o occupational noise: OR = 1.53 (95% CI 1.03–2.29) |
Self-reported smoking may have been understated |
Pure-tone hearing thresholds(audiometers calibrated to ISO 389 standard) Frequencies tested: 0.5, 1, 2, 3, 4, 6, 8 kHz Age adjustment: measured hearing thresholds transformed to values at age 18 (ISO 7029) |
Analysis of Covariance Covariant: exposure time to noise Significant effect of heavy or very heavy lifetime smoking on age-adjusted hearing thresholds: 3 kHz (right p = .044, left p = .001) 4 kHz (right p = .055, left p = .086) Not significant at other frequencies |
Very heavy and heavy smokers tended to use noisier tools than the moderate and nonsmokers Non-, moderate, and heavy smokers used hearing protectors more often (61–64%) than very heavy smokers (47%) |
TABLE D-4 Progression of Hearing Loss After Noise-Induced Hearing Loss
Citation |
Design |
Population |
Exposures and Source of Exposure Data |
Lee et al. (2005) |
Longitudinal cohort |
188 participants (91 women, 97 men); 376 ears Participation for at least 3 yrs (mean 6.4 yrs) Ages at entry: 60–81 yrs (mean 68 yrs) Recruitment through advertisements and referral, began in 1987 Conventional thresholds tested annually Exclusions: conductive hearing loss, active otologic/neurologic disease Longitudinal study of presbyacusis, Medical University of South Carolina |
Questionnaire: noise history, medication use, self-evaluation of hearing handicap History of noise exposure: 56 of 85 men 18 of 78 women |
Outcome Measure |
Results |
Comments |
Rate of change in pure-tone hearing thresholds (0.25, 0.5, 1, 2, 3, 4, 6, 8 kHz) (slope from linear regression of changes for each ear) Testing also done for extended high frequencies |
No significant difference in rate of threshold change at 1–2 kHz for noise-exposed and unexposed Rate of change at 6–8 kHz lower for noise-exposed than unexposed males; lower at 2 kHz for noise-exposed females Hearing thresholds at 2–8 kHz were significantly higher (7.7 to 12.1 dB, p < 0.05) for noise-exposed men Noise-exposed women had smaller threshold elevations (2.2 to 7.6 dB) Overall, men had significantly poorer initial thresholds than women at 2–8 kHz Rates of change at 0.25–2 kHz had positive correlations w/ initial thresholds at higher frequencies Rates of change at 3–8 kHz had negative correlations w/ initial thresholds at those frequencies |
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Citation |
Design |
Population |
Exposures and Source of Exposure Data |
Cruickshanks et al. (2003) |
Longitudinal cohort |
Baseline (1993) 3,753 participants, ages 48 to 92 years 1,925 w/o hearing loss [PTA (0.5, 1,2,4 kHz) in both ears ≤ 25 dB] Mean age: 61 yrs 1,631 w/ hearing loss [PTA (0.5, 1,2,4 kHz) in either ear > 25 dB and < 100 dB in worse ear] Mean age: 71 yrs 5-yr follow-up (1998) 2,800 participants Losses to death, refusal, loss to follow-up; losses greater among persons w/ hearing loss Epidemiology of Hearing Loss Study, Beaver Dam, WI |
Questionnaires: occupation and exposure to occupational noise, leisure noise, military service |
Rosenhall (2003) |
Mixed longitudinal and cross-sectional cohort |
Gerontological and geriatric population study, Gothenburg, Sweden Total population: 616 men 869 women Cohorts 1. 1971, 70 yr olds; seven exams, to age 90 yrs; cohort supplemented beginning at age 85 2. 1976, 70 yr olds; second exam at 75 yrs 4. 1990–1991, 75 yr olds 5. 1992–1993, 70 yr olds |
Questionnaires: occupation and exposure to occupational noise |
Outcome Measure |
Results |
Comments |
Incident hearing loss PTA (0.5, 1, 2, 4 kHz) in either ear > 25 dB at follow-up |
Incident hearing loss All: 21% (95% CI 19.4–23.4) Men (age-adj): 31% (CI 26.8–34.6) Current or former occupation (age-, sex-adj): Mgmt/profess: OR = 1.00 Production: OR = 1.92 (95% CI 1.10–3.37) Operations/fabricators: OR = 1.92 (95% CI 1.26–2.93) Self-reported occupational noise exposure: not significant |
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Progression of hearing loss PTA (0.5, 1, 2, 4 kHz) > 5 dB increase over baseline level |
Progression of hearing loss All: 53.5% (CI 50.2–56.4) Men (age-adj): 51.5% (CI 47.0–55.2) Occupation: no significant assoc between likely noise exposure and progression |
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Change in pure-tone hearing thresholds (0.25, 0.5, 1, 2, 4, 6, 8 kHz) from age 70 to age 75 yrs |
Greater increases in hearing thresholds at 1, 2, 8 kHz for men exposed to noise than men not exposed Increases at 4 kHz similar for exposed and nonexposed Less change between ages 75 and 79; similar changes for exposed and nonexposed |
No measures of statistical significance reported |
Outcome Measure |
Results |
Comments |
15-year change (E22–E15) in audiometric threshold for 8 frequencies: 0.25–8 kHz (each ear assessed separately) Secondary analysis included as predictor variables cardiovascular disease events (lifetime), smoking history (E15–E22), number of prescription medications used regularly (E15–E22) |
0.25, 0.5, 1 kHz: threshold shifts not significantly different across notch groups 2 kHz: notch groups are significantly different; (e.g., LE shifts: N0 = 12.4; N1 = 16.0; N2 = 18.8; p = 0.0018) 4, 6 kHz: N2 shifts significantly smaller than N0, N1 8 kHz: N1 shift significantly greater than N0 or N2; N0 and N2 not significantly different With E15 thresholds as covariates, notch category was significant only at 2 kHz (p < .001) Similar patterns for right and left ears Results adjusted for age, smoking, medications |
Actual noise exposures during E15–E22 interval not documented; presumed no additional occupational noise exposure for most subjects and little recreational exposure Past noise exposure inferred from presence of audiometric notch Possible survival bias |
TABLE D-5 Features of Studies Included in Analysis of Hearing Loss Among Military Personnel
Citation |
Design |
Timing of Data Collection |
Study Population |
Stratification |
a. Air Force Studies |
||||
Sutherland and Gasaway (1976) |
Cross-sectional |
Jan–June 1975 Data from AF Form 1490 (annual hearing conservation audiogram), received Jan–Jun 1975 |
56,951 USAF personnel (men only?) 48,262 military 8,689 civilians Personnel tested as part of the hearing conservation program |
Age (yrs) 18–24; 25–34; 35–44; 45–54; 55–64 |
Sutherland and Gasaway (1978) |
Cross-sectional |
1 June 1975–31 May 1976 Data from AF Form 1490 (annual hearing conservation audiogram) for test dates w/in study period |
117,454 USAF personnel (men only?) 99,318 military 18,136 civilians Received annual hearing conservation audiogram during 1-yr study period (one record/person) |
Age (yrs) 18–24; 25–34; 35–44; 45–54; 55–64 |
Thomas (1995) |
Longitudinal and cross-sectional reporting |
Not specified Data from Air Force hearing conservation program test results |
6,655 persons in hearing conservation program (8 bases) 3,029 military 2,859 civilians 6,207 men 365 women Only personnel with at least 4 sequential audiograms |
Tests 1–4 (mean age for personnel at each test) |
Freqeuencies Tested |
Audiometric Zero, Audiometer, and Earphones |
Summary Measures Reported* |
Comments, Conclusions |
0.5, 1, 2, 3, 4, 6 kHz |
ANSI, 1969 TDH-39 earphones w/ MX-41/AR cushions |
Median hearing threshold levels (military and civilians reported separately) % distribution of HTLs for each frequency % STS |
Hearing levels of military noise-exposed USAF personnel better than USAF civilians and U.S. population (except at ages 18–24, 0.5 kHz, left ear). |
0.5, 1, 2, 3, 4, 6 kHz |
ANSI, 1969 TDH-39 earphones w/ MX-41/AR cushions |
Median hearing threshold levels (military and civilians reported separately) % distribution of HTLs for each frequency % STS |
Noise-exposed USAF military personnel show better hearing than noise-exposed USAF civilians and general U.S. population |
0.5, 1, 2, 3, 4, 6 kHz |
Not specified |
Mean hearing threshold levels (ears not reported separately) (military and civilians reported separately) % worse on subsequent test % better or worse on subsequent test |
Total personnel in hearing conservation program was 14,166 Less variability in women’s HTLs than men’s (combined military and civilian) Analysis of variability of HTLs classifies USAF hearing conservation program as unacceptable to marginal |
Citation |
Design |
Timing of Data Collection |
Study Population |
Stratification |
b. Army Studies |
||||
Walden et al. (1971) |
Cross-sectional (pilot study) |
1971 (Sept–Nov?) |
2,726 men Active duty Officers and enlisted Included recruits, advanced trainees, regular personnel from infantry, armor, artillery, pilots Convenience sample from 6 bases |
Age (yrs) 16–20; 21–25; 26–30; 31–35; 36–40; 41–45; 46–50; 51–55 LOS (yrs): 0–2; 2–4; 4–6; 6–8; 8–10; 10–15; 15–20; 20–25; 25–30; (w/in branches: < 4, 4–10, > 10 yrs) |
Walden et al. (1975) |
Cross-sectional |
June 1974–Sept 1974 |
3,000 enlisted men (10 bases; 1,000 each infantry, armor, and artillery) 75% of active duty spent in designated branch 300 male inductees (3 bases) Random selection |
Branch LOS (yrs): 1.5–2.4; 2.5–7.4; 7.5–12.4; 12.5–17.4; 17.5–22.4 |
Peters and Ford (1983) |
Cross-sectional |
Feb–Aug 1982 |
145 aviators (all men?) Ft. Rucker; officers and warrant officers Age range 24–45 yrs (mean 32 yrs) 54% w/ substantial exposure to small arms and artillery fire Random sample |
Flight hours 50–400; 401–600; 601–800; 801–1000; 1001–2000; 2001–3000; 3001–4000; 4001–5000; 5001–6000; 6001–7000 |
Frequencies Tested |
Audiometric Zero, Audiometer, and Earphones |
Summary Measures Reported* |
Comments, Conclusions |
0.25, 0.5, 1, 2, 4, 6 kHz |
ISO, 1964 Portable audiometers w/ minimum threshold of -10 dB HL |
Mean hearing thresholds (standard deviation) % distribution by hearing profile |
Higher % with hearing impairment w/ longer active duty service Higher thresholds seen as early as first 4–6 months of active duty Authors cite need for longitudinal study |
0.25, 0.5, 1, 1.5, 2, 3, 4, 6, 8 kHz < 81 dBA exposure in 14 hours before test |
ANSI, 1969 Manual testing w/ audiometers and test booths available at each base TDH-39 earphones w/ MX-41/AR cushions |
Mean hearing thresholds (standard deviation) % distribution by hearing profile (standard error) |
Hearing ability decreases as time-in-service increases Clinically significant losses: 20–30% at ≥ 2 yrs LOS; > 50% at ≥ 15 yrs LOS Middle to high frequencies most affected Assigned hearing profile category not correct for many |
2, 3, 4, 6 kHz |
ANSI, 1969 Grason-Stadler audiometer, Model 1701 w/ TDH 49 earphones or Grason-Stadler GSI 10 w/ TDH 50P earphones |
Mean and median hearing thresholds (standard deviation, standard error) |
Mean thresholds lower (better) than aviators in Walden et al. (1971) Thresholds higher for left ear at 2, 4 kHz, higher for right ear at 6 kHz Significant effect of flight hours (50–400; 401–3000; 3001–6000 hrs) on left-ear threshold differences between 4 and 2 kHz |
Citation |
Design |
Timing of Data Collection |
Study Population |
Stratification |
Chandler and Fletcher (1983) |
Retrospective analysis of longitudinal data |
Date not specified Reference and current audiograms (w/in past 12 mos) |
209 men in six engineering MOS (1) Basic engineers; (2) carpenters, plumbers, electricians; (3) heavy equipment operator/ mechanic; (4) maintenance (wheeled vehicle); (5) truck driver; (6) petroleum supply and storage Exclusions: history of nonoccupational noise hazards, head or acoustic trauma, middle-ear pathology, or family history of hearing loss Age range: 18–50 yrs |
MOS |
Ohlin (1992) |
Cross-sectional |
1989 Hearing conservation program reports Last test in 1989 DD Form 2215:1,284 tests DD Form 2216:1,625 tests |
2,903 enlisted men (10 bases: 985 Infantry; 963 Armor; 959 Artillery) Random selection from registry for hearing conservation program 3,534 inductees (1 base) Test results from feasibility study for reference audiograms No otologic examinations |
LOS (yrs) 1.5–2.4; 2.5–7.4; 7.5–12.4; 12.5–17.4; 17.5–22.4 yrs Branch (w/o LOS) |
Frequencies Tested |
Audiometric Zero, Audiometer, and Earphones |
Summary Measures Reported* |
Comments, Conclusions |
0.5, 1, 2, 3, 4, 6 kc/s |
ANSI, 1969 No information on audiometer or earphones |
Mean hearing threshold levels (current) Change from reference thresholds (graphed data only) |
No remarkable differences among MOS groups Better current HTLs at 3, 4, and 6 kc/s by 23–34 dB, than 1954 data for comparably aged men working in industry may reflect exclusions for other causes of hearing loss in military population |
0.5, 1, 3, 4, 6 kHz (no quiet period required before DD Form 2216 test) |
Standard hearing conservation program calibration HEARS microprocessor audiometers; group testing Circumaural test earphones (Audiocups) |
Mean hearing thresholds (average of left and right ears) (standard error) % distribution by hearing profile (standard error) |
59% of enlisted combat arms personnel from sampled bases in HEARS in 1989 Entrance standards stricter as of 1 Aug 87 (AR 40-501) No data on race or nonoccupational noise Systematic increase in HTLs with increase in LOS, w/ approx 50% of hearing loss attributed to aging Differences among branches not clinically significant Improvements over 1974 levels for all LOSs |
Citation |
Design |
Timing of Data Collection |
Study Population |
Stratification |
Henselman et al. (1995) |
Cross-sectional |
1989 Records from hearing conservation program tests (high-noise MOS) and periodic physical examinations (low-noise MOS) |
39,006 enlisted men from high-noise-exposure MOS (infantry, armor, artillery) 18,730 enlisted men from low-noise-exposure MOS (administration, supply and services, medical, visual information, electronic maintenance and calibration, public affairs, automated data processing, topography, intelligence) Age range: 17–56 yrs |
Race (white black, other), LOS (yrs): by yr for 0–14.9 yrs; 15–19.9; 20–24.9 yrs |
c. Navy and Marine Corps Studies |
||||
Robertson et al. (1978) |
Cross-sectional |
“[N]early three years” (mid 1970s? dates not specified) |
3,050 enlisted sailors: 1,561 in “experimental” ratings (high noise exposure expected: airman, fireman, equipment operator, machinist mate, engineman, boiler tech, aviation mechanic, aviation machinist mate, aviation boatswain mate, aviation ordnance man) |
LOS (yrs) For ratings: 1–2; 2–3; 3–4; 4–5; 5–10; 10–15; 15–20; 20–25 yrs For apprentices: 1–2; 2–3; 3–4 yrs |
Frequencies Tested |
Audiometric Zero, Audiometer, and Earphones |
Summary Measures Reported* |
Comments, Conclusions |
0.5, 1, 2, 3, 4, 6 kHz |
Standard hearing conservation program calibration Tracor RA 600AM microprocessor audiometer TDH-39 earphones with ear cushions |
Age-corrected threshold average (1, 2, 3, and 4 kHz; left and right ears averaged) Age correction from ISO-1999, database B |
Analyzed records cover 25% of total personnel in high-noise MOS and 18% of personnel in low-noise MOS Exposure categories based on current MOS; no information on noise-exposure history No control for nonoccupational noise Significant difference in average thresholds between high-and low-noise groups, but differences were < 5 dB |
0.5, 1, 2, 3, 4, 6, 8 kHz |
ANSI, 1969 Manual audiometry No information on audiometer or earphones |
“Average” hearing threshold levels (standard deviation) % of subjects with significant high- and low-frequency hearing losses ( ≥ 30 dB) |
37% of experimental group and 23% of control group had significant high-freq hearing losses at ≥ 5 yrs of service USMC high-freq losses described as generally greater than Navy; only those for Navy EO rating similar to USMC |
Citation |
Design |
Timing of Data Collection |
Study Population |
Stratification |
|
|
|
1,489 in “control” ratings (low noise exposure expected: hospitalman, dentalman, hospital corpsman, dental tech, mess management spec., yeoman, personnelman, disbursing clerk, training device tech, aviation maintenance admin) 361 apprentices (airman, fireman, hospitalman, dentalman) 121 recruits 298 women (9% overall: 18% of recruits: 16% of control; 1.7% of experimental) “Subjects were identified by computer” Exclusions: conductive hearing loss |
|
Goldenberg (1977) |
Cross-sectional |
13-month period (early 1970s? date not specified) |
11,577 men (Marine Corps enlisted personnel and officers) Consecutive unique test subjects at one site No otologic examination |
Age (yrs) < 18; 18–24; 25–34; 35–44; 45–54; 55–64 |
Frequencies Tested |
Audiometric Zero, Audiometer, and Earphones |
Summary Measures Reported* |
Comments, Conclusions |
0.5, 1, 2, 3, 4, 6 kHz |
ISO (1964) Rudmose ARJ-4A audiometer, 10-man booth TDH-39 earphones If questionable self-recording audiogram, retested in 1-man booth w/ Beltone 15 CW audiometer, TDH-39 earphones |
Median hearing thresholds (better ear only; graphed data) % w/ > 25 dB and % w/ > 45 dB loss at avg of speech frequencies (0.5, 1, 2 kHz) or high frequencies (3, 4, 6 kHz) |
Marine Corps data similar to USPHS for civilians Markedly higher thresholds at ages 35–44 yrs and older |
Frequencies Tested |
Audiometric Zero, Audiometer, and Earphones |
Summary Measures Reported* |
Comments, Conclusions |
0.5, 1, 2, 3, 4, 6 kHz |
Not reported; reference to testing according to NEHC guidance |
Mean hearing thresholds (standard deviation) |
Mean thresholds for USN and USMC were generally worse than OSHA age-adjusted values Women had lower thresholds than men w/in each service at corresponding ages |
0.5, 1, 2, 3, 4, 6 kcps |
ASA, 1951 Beltone audiometers, TDH-39 earphones w/ MX-41/AR cushions Minimum threshold: −10 dB HL |
Median hearing thresholds (method for calculating 95% confidence intervals described) % distribution by hearing threshold categories |
No noise-exposure history Hearing levels higher w/ age from youngest to oldest |
TABLE D-6 Studies on Prevalence of Tinnitus and Prevalence of Tinnitus with Hearing Loss
Study |
Design, Population |
Definition of Tinnitus |
Definition of Hearing Level or Hearing Loss |
a. Community-based Studies |
|||
Sindhusake et al. (2003a,b, 2004) Blue Mountains Hearing Study, Australia, 1997 |
Cross-sectional 2,015 persons, ages 55+ yrs (mean 70 yrs) Residents of 2 suburban postal code areas |
Tinnitus Sounds persisting for 5 minutes or longer during the past yr |
Hearing level Lower frequencies: PTA for 0.5, 1, 2, and 4 kHz Higher frequencies: PTA for 4, 6, and 8 kHz Hearing loss PTA for 0.5, 1, 2, and 4 kHz > 25 dB HL in better ear Pure-tone testing at 0.25, 0.5, 1, 2, 4, 6, 8 kHz (3 kHz if 20 dB difference b/t 2 and 4 kHz) |
Hoffman and Reed (2004) Tambs et al. (2003) Nord-Trøndelag Hearing Loss Study, Norway, 1995–1997 |
Cross-sectional 51,975 persons, ages 20–101 yrs (mean: 50 yrs) Residents of Nord-Trøndelag County |
Tinnitus Bothered by ringing in the ears |
Hearing loss PTA for 0.5, 1, 2, and 4 kHz in worse ear: ≤ 25 dB HL > 25, ≤ 40 dB HL > 40 dB HL |
Noise Exposure and Source of Exposure Data |
Prevalence of Tinnitus |
Prevalence of Tinnitus, by Hearing Level |
Comments |
Questionnaire on noise exposure Duration (yrs) and level of occupational noise (quiet; tolerable; “unable to hear speech”) Noise during military service Leisure noise (e.g., gunfire) |
30% w/ tinnitus Age- and sex-standardized to Australian population |
Hearing loss 35% w/ tinnitus Normal hearing 27% w/ tinnitus |
75% participation rate for eligibles |
Questionnaire on noise exposure Occupational noise: difficult to have a conversation; type of work; exposed to staple gun, hammering, chain saw, blasting, etc; Other noise: impulse noise (y/n); brass band; personal stereo |
15% w/ tinnitus |
Odds ratio for tinnitus ≤ 25 dB HL Men: 1.0 Women: 1.0 > 25, ≤ 40 dB HL Men: 2.84 (95% CI 2.55–3.16) Women: 2.78 (95% CI 2.45–3.15) > 40 dB HL Men: 4.18 (95% CI 3.66–4.77) Women: 5.40 (95% CI (4.67–6.24) |
Possible response bias Participation rates were 65% for men; 73% for women; < 50% for ages < 30 yrs; ≥ 75% for ages 50–80 yrs |
Study |
Design, Population |
Definition of Tinnitus |
Definition of Hearing Level or Hearing Loss |
Nondahl et al. (2002) Epidemiology of Hearing Loss Study, Beaver Dam, WI 1993–2000 |
Cross-sectional and longitudinal Baseline 3,737 participants, ages 48 to 92 years 5-yr follow-up 2,558 participants (75% of those w/o significant tinnitus at baseline) |
Significant tinnitus “buzzing, ringing, or noise” in the ears in the past year, rated as at least moderately severe or causing problems w/ sleep or both Excludes tinnitus rated mild or of unknown severity and not causing problems w/ sleep |
Hearing loss PTA of thresholds at 0.5, 1, 2, and 4 kHz > 25 dB HL in worse ear Pure-tone testing at 0.25, 0.5, 1, 2, 3, 4, 6, 8 kHz |
Palmer et al., (2002) United Kingdom, 1997–1998 |
Cross-sectional 12,907 responses from adults, ages 16–64 yrs Postal survey using random sample from age-sex registers for 34 general medical practices, plus members of the armed services |
Tinnitus Noises lasting longer than 5 minutes during the past 12 months Persistent tinnitus Occurring most or all of the time |
No hearing difficulty Report of no or slight difficulty hearing a person talking in a quiet room w/ better ear Severe hearing difficulty Use of a hearing aid or report of severe difficulty hearing or inability to hear a person talking in a quiet room Intermediate hearing difficulty All others No audiometric testing done |
Noise Exposure and Source of Exposure Data |
Prevalence of Tinnitus |
Prevalence of Tinnitus, by Hearing Level |
Comments |
Occupational noise history - full-time job required using loud voice to be heard at 2 ft; - farmer who drove tractor w/out cab at least half of the time; or - military duties on aircraft; tracked vehicle, ship engine room; on weapons range ≥ 7 times per yr; used grenades, mortars, or shoulder-held grenade launchers; used weapons system requiring more than one operator |
Baseline (significant tinnitus) 8% [8.2%; 95% CI 7.4–9.1] Severe: 1.5% Moderate or causing sleep problems: 6.7% 5-yr Incidence 6% [5.7%; 95% CI 4.8–6.6] |
Baseline w/ hearing loss 12% w/ significant tinnitus w/o hearing loss 5% w/ significant tinnitus |
|
Questionnaire response on number of years working in noisy places (need to shout to be heard) |
Persistent tinnitus Men: 6% Women: 3% |
W/ severe hearing difficulty Men: 16.1% w/ persistent tinnitus (age-standardized) Women: 33% w/ persistent tinnitus W/ no hearing difficulty Men: 5.0% w/ persistent tinnitus Women: 3% w/ persistent tinnitus |
Possible response bias (58% response rate) |
Study |
Design, Population |
Definition of Tinnitus |
Definition of Hearing Level or Hearing Loss |
Adams et al. (1999) National Health Interview Survey, United States, 1996 |
Cross-sectional 63,402 persons, all ages Nationally representative random sample; noninstitutionalized population; excludes armed forces and nursing home residents |
“Does [household member] now have tinnitus or ringing in the ears?” |
|
Hoffman and Reed (2004) Adams and Marano (1995) Disability Supplement, National Health Interview Survey, United States, 1994–1995 |
Cross-sectional, household interviews 99,435 adults, ages 20 yrs and older Subset of participants in national sample of noninstitutionalized population; excludes armed forces and nursing home residents Excludes proxy responses on tinnitus |
“Does [household member] have ringing, roaring or buzzing in the ears or head now that has lasted for at least 3 months?” |
Moderate or worse hearing loss (subjective assessment, criteria not specified) Uses hearing aid |
Hoffman and Reed (2004) Adams and Benson (1991) Hearing Supplement, National Health Interview Survey, United States, 1990 |
Cross-sectional, household interviews 59,343 adults, ages 20 yrs and older Subset of participants in national sample of noninstitutionalized population; excludes armed forces and nursing home residents Excludes proxy responses on tinnitus |
“At any time over the past 12 months, have you ever noticed ringing in the ears, or have you been bothered by other funny noises in your ears or head?” If yes: Occurs all the time/ every few days/ less often Bothered quite a bit/ just a little/ not at all |
Moderate or worse hearing loss (subjective assessment, criteria not specified) |
Noise Exposure and Source of Exposure Data |
Prevalence of Tinnitus |
Prevalence of Tinnitus, by Hearing Level |
Comments |
No exposure data |
3% w/ tinnitus Age < 45 yrs: 1% 45–64 yrs: 6% 65+ yrs: 9% 18+ yrs: 4% 45+ yrs: 7% |
|
94% participation rate |
|
4% w/ tinnitus |
Moderate or worse hearing loss 32% w/ tinnitus Uses hearing aid 12% w/ tinnitus |
Unknown effect of exclusion of proxy responses on representativeness of data (40,570 adult proxy responses) |
No exposure data |
8% w/ tinnitus |
Moderate or worse hearing loss 42% w/ tinnitus |
Unknown effect of exclusion of proxy responses on representativeness of data (27,364 proxy responses) |
Study |
Design, Population |
Definition of Tinnitus |
Definition of Hearing Level or Hearing Loss |
Coles (1996) Tier B, National Study of Hearing, United Kingdom |
Cross-sectional 3,234 people selected in stratified random sample from postal survey responses Stratification to ensure larger proportion of persons w/hearing disorders and tinnitus |
Prolonged spontaneous tinnitus: lasting at least 5 minutes and not temporarily induced by noise, drugs, or ear or respiratory illness |
Hearing threshold levels |
Medical Research Council’s Institute of Hearing Research, (1981) Coles (1984) Tier A, National Study of Hearing, United Kingdom, 1978–1982 |
Cross-sectional (multiple samples) Postal survey, responses from random samples of adults, age 17+ yrs, from 4 cities: Prepilot: 522 Pilot: 5,000 (74%) Phase I: 8,069 Phase II: 7,645 |
Prolonged spontaneous tinnitus lasting at least 5 minutes and not temporarily induced by noise, drugs, or ear or respiratory illness Prepilot Ever noticed noises in your head Spontaneous tinnitus Pilot Ringing or buzzing lasting 5 minutes or more, excluding those occurring only after exposure to loud noise Phase I Ever have noises lasting 5 minutes or more, excluding those occurring only after exposure to loud noise |
|
Noise Exposure and Source of Exposure Data |
Prevalence of Tinnitus |
Prevalence of Tinnitus, by Hearing Level |
Comments |
|
|
Presence of moderately or severely annoying tinnitus HTL 10–19 dB vs HTL < 10 dB OR=2 HTL >80 dB vs HTL < 10 dB OR= 27 |
Controlling for hearing thresholds eliminates associations w/ age, noise exposure, or socioeconomic status |
Little or no occupational noise exposure: 8% w/ tinnitus High lifetime noise dose: 21% w/ tinnitus |
Prolonged, spontaneous 10% Any tinnitus 34% to 39% Brief or nonspontaneous 23% to 27% Spontaneous 11% to 18% Moderately or severely annoying: 5% Sleep-disturbing: 5% Severe effect on quality of life: 1% Severe effect on ability to lead a normal life: 0.5% |
|
80% response rate 7% of all adults have sought a doctor’s help for tinnitus |
Study |
Design, Population |
Definition of Tinnitus |
Definition of Hearing Level or Hearing Loss |
|
|
Phase II “Nowadays” noises lasting 5 minutes or more, excluding those occurring only after exposure to loud noise |
|
Parving et al. (1993) Copenhagen Male Study, Denmark, 1985–1986 |
Cross-sectional assessment of tinnitus 3,387 men, ages 53–75 in 1985–86 Participants in a prospective cohort study of cardiovascular health |
Tinnitus of greater than 5 minutes duration |
Self-assessed hearing ability: do you think your hearing is affected? |
Rosenhall and Karlsson (1991) Gothenburg, Sweden, 1971–1976 |
Repeated cross-sectional assessments of defined cohorts Cohorts F01:377 initial members; born 1901–02; first examined in 1971 F06:297 initial members; born 1906–07; first examined in 1976 Gerontological and geriatric population study |
Tinnitus (buzzing): none, occasional, continuous |
Pure-tone thresholds at 0.25, 0.5, 1, 2, 4, and 8 kHz |
Noise Exposure and Source of Exposure Data |
Prevalence of Tinnitus |
Prevalence of Tinnitus, by Hearing Level |
Comments |
|
17% w/ tinnitus |
Significantly higher prevalence of tinnitus if hearing affected (X2, p < 0.001) Hearing affected: Yes: 27% w/ tinnitus No: 11% w/ tinnitus |
|
|
Continuous tinnitus F01 Age 70:8% Age 75:12% Age 79:11% F06 Age 70:12% Occasional tinnitus F01 Age 70:20% Age 75:17% Age 80:30% F06 Age 70:19% |
|
|
Study |
Design, Population |
Definition of Tinnitus |
Definition of Hearing Level or Hearing Loss |
Axelsson and Ringdahl (1989) Gothenburg, Sweden, 1980s |
Cross-sectional 2,378 responses from adults, ages 20–79 yrs Postal survey using age-stratified random sample from city population register |
Do you suffer from tinnitus? (never/seldom/often/always) Additional characterization of tinnitus only for those responding “often” or “always” |
Subjective hearing: - normal - some hearing loss - marked hearing loss - deaf |
Roberts (1968) Health Examination Survey, United States, 1960–1962 |
Cross-sectional 6,672 adults, ages 18–79 yrs Nationally representative random sample; noninstitutionalized population; excludes armed forces and nursing home residents |
“At any time over the past few years, have you ever noticed ringing (tinnitus) in your ears of have you been bothered by other funny noises in your ears?” If yes, how often (every few days / less often) If yes, do they bother you (quite a bit / just a little) Severe and mild tinnitus not explicitly defined |
Average thresholds Better than normal: −5 dB HL or better Normal: −4 dB to 15 dB HL Some hearing impairment: 16 dB HL or worse Average of thresholds at 0.5, 1, and 2 kcps (audiometric zero: ASA, 1951) Testing at 0.5, 1, 2, 3, 4, 6 kcps |
Noise Exposure and Source of Exposure Data |
Prevalence of Tinnitus |
Prevalence of Tinnitus, by Hearing Level |
Comments |
|
Tinnitus Always: 6% Often: 8% Seldom/never: 86% |
|
Response rate: 66% (usable responses) |
No exposure data |
32% w/ tinnitus Severe: 6% Mild: 27% |
W/ better than normal hearing 3% w/ tinnitus W/ some hearing impairment 22% w/ tinnitus |
|
Study |
Design, Population |
Definition of Tinnitus |
Definition of Hearing Level or Hearing Loss |
b. Industrial Workers |
|||
Sulkowski et al. (1999) Poland |
Cross-sectional 261 male drop-forge operators Age range: 18–61 yrs (mean: 31 yrs) Employment: 1–28 yrs (mean: 10 yrs) 169 age-matched controls from low-noise factory areas (mean age: 35 yrs) Exclusions: ear disease or pre-employment noise exposure |
No definition provided Interview to determine presence and characteristics of tinnitus |
Pure-tone audiometric testing before the beginning of the workday |
Griest and Bishop (1996) Oregon, 1971–1990, 1992 |
Longitudinal (retrospective cohort) 138 men in steel foundry hearing conservation program Initial ages: 18 to 41 yrs (mean 28 yrs) No exclusions for other tinnitus risk factors |
Tinnitus reported at annual audiogram (never / 1–2 times / 3+ times) Tinnitus reported on 1992 questionnaire: Ever hear ringing noises or other sounds When first aware How often (rarely / several times a month / several times a week / several times a day / always there) How long (only a few minutes / several hours / several days / always there) |
Annual audiograms starting in 1971 Threshold at 4 kHz for men 20–29 yrs in 1971 |
Noise Exposure and Source of Exposure Data |
Prevalence of Tinnitus |
Prevalence of Tinnitus, by Hearing Level |
Comments |
Noise survey; 0.34 impulses per second Hearing protectors not worn regularly |
Noise-exposed 70% w/ tinnitus Controls 4% w/ tinnitus |
|
|
Noise levels: TWA of 85 to 101 dBA Exposure of ≥ 85 dBA for 10 yrs or more Sound surveys and dosimetry from 2 to 4 hour exposures Hearing protection use recorded |
Tinnitus reports at audiograms Never: 62% 1–2 times: 17% 3+ times: 20% Tinnitus reports on questionnaire Never: 39% Rarely / several times a month: 43% Several times a week or more: 17% Significant association between frequency of tinnitus reports at audiogram and report of tinnitus several times a week or more in questionnaire (X2, p < 0.0001) |
|
Tinnitus at baseline not excluded For 20- to 29-yr olds at baseline, no significant differences between those reporting any tinnitus and no tinnitus in military, recreational, or other occupational noise exposure |
Study |
Design, Population |
Definition of Tinnitus |
Definition of Hearing Level or Hearing Loss |
Gabriels et al. (1996) Western Australia |
Cross-sectional 38,725 otologically normal, noise-exposed workers given baseline hearing tests required by workers compensation program Age range:16–55+ yrs Noise exposure: 0–25+ yrs Exclusions: indications of hearing loss from injury or disease |
Tinnitus: Yes to “Do you ever have ringing noises … which last more than 5 minutes?” (yes/ no / maybe) |
Noise-induced hearing loss Age-corrected “percentage loss of hearing” > 0% Percentage loss of hearing calculated from Australian National Acoustic Laboratory tables specific for age and sex Tested at 0.5, 1, 1.5, 2, 3, 4, 6, 8 kHz; 16 hrs of prior quiet |
Phoon et al. (1993) Singapore, 1990 |
Cross-sectional 647 workers from 808 workers identified as having noise-induced hearing loss through annual monitoring audiograms Mean age: 39 yrs Exclusions: ear disease, ear drum abnormality, conductive hearing loss |
Interview at follow-up examination: Any tinnitus w/in past 6 months? Frequency: all the time/ once a day/ ≥ once a week/ < once a week/ not sure |
Hearing loss (average of thresholds at 1, 2, 3 kHz) Early: ≤ 25 dB HL Intermediate: > 25, < 50 dB HL Late: ≥ 50 dB HL |
Noise Exposure and Source of Exposure Data |
Prevalence of Tinnitus |
Prevalence of Tinnitus, by Hearing Level |
Comments |
Workplace exposure of 8-hr TWA of 90 dBA, or peak 140 dB |
18% w/ tinnitus 10% maybe tinnitus |
>10% NIHL 37% w/ tinnitus 0% NIHL 16% w/ tinnitus |
No significant differences for age or number of years of noise exposure |
Assumed to be 8-hr time weighted average ≥ 85 dBA (basis for requirement for annual testing) |
23% w/ tinnitus No significant differences by age, duration of noise exposure W/ tinnitus (n=151) Once a day or more: 34% < once a week: 39% Excluded cases 42% w/ tinnitus |
Hearing loss Early: 20% w/ tinnitus Intermediate: 30% w/ tinnitus Late: 27% w/ tinnitus Prevalence significantly lower in early hearing loss cases than intermediate and late cases (X2, p = 0.02) |
Consulted a doctor: 14% Interfered w/ sleep: 14% Interfered w/ some daily activity: 30% |
Study |
Design, Population |
Definition of Tinnitus |
Definition of Hearing Level or Hearing Loss |
Neuberger et al. (1992) Austria, 1984–1986 |
Cross-sectional 110,647 noise-exposed factory workers Documented noise-exposure history: > 4 hr daily, > 85 dBA for ≥ 6 months Ages 15–65 yrs (median: 38 yrs) Exclusions: insufficient or unspecified noise exposure |
No definition provided |
Roeser speech impairment index = 0.5 (HL 3 kHz) + HL 1 kHz − 15 Impairment: Index > 10% Pure-tone thresholds at 0.25 to 8 kHz (only results for left ears included in analysis) |
Kamal et al. (1989) Egypt |
Cross-sectional 88 forge hammering workers Age range: 30–60 yrs Noise exposure: 9–25 yrs Exclusions: ear infections |
No definition provided Interview to obtain tinnitus reports |
Pure-tone audiometric testing at 0.25, 0.5, 1, 2, 4, 6, 8 kHz Each worker tested before and after a work shift |
Chung et al. (1984) British Columbia |
Cross-sectional 33,168 workers in industrial hearing conservation programs Exclusions: history of ear disease, head injury, ear surgery, relative w/ hereditary hearing loss; current day-to-day changes in hearing, ruptured ear drum |
From medical history interview: “do you now have ringing in your ears?” (instruction to interviewers: tinnitus present more than momentarily and at least recurring if not continuous) |
Audiometric surveillance records for annual testing for hearing conservation programs |
Noise Exposure and Source of Exposure Data |
Prevalence of Tinnitus |
Prevalence of Tinnitus, by Hearing Level |
Comments |
Median noise exposure: 90.5 dBA SPL Worksite records of A-weighted noise levels Self-report of previous noise exposure Self-reported hearing protector use: seldom (< 10% of work time), occasional (10–50%), or continuous (> 50%) |
7% w/ tinnitus Rates described as higher w/ increasing hearing loss and w/ history of ear disease or head injury |
|
93% exposed to steady-state noise Noise levels recorded w/ most recent audiogram attributed to prior periods of noise-exposed work (attribution justified by low workforce turnover) |
Noise measured at workers’ ears Background: 92–94 dBA Hammer: 120–135 dBA No hearing protection used |
88% w/ tinnitus |
|
|
Assumed to be 8-hr TWA ≥ 85 dBA (basis for requirement for annual testing) Reports on shooting history |
7% w/ tinnitus No association w/ age, smoking history (current or past), or shooting history after controlling for hearing thresholds |
All thresholds ≤ 25 dB HL: 3% w/ tinnitus |
|
Study |
Design, Population |
Definition of Tinnitus |
Definition of Hearing Level or Hearing Loss |
c. Military Personnel |
|||
Attias et al. (2002) Israel |
Cross-sectional 2,200 male soldiers Random selection of noise-exposed personnel routinely screened for hearing problems Age: 22–50 yrs |
Do you experience or hear sounds when no sound source appears to be present? Interview to determine tinnitus onset, variability, impact |
Noise-induced hearing loss Average threshold at 2–8 kHz ≥ 25 dB HL Pure-tone audiometric testing |
Ylikoski and Ylikoski (1994) Finland |
Cross-sectional 699 male Finnish army officers Age-stratified random sample Mean age: 39.8 yrs (median 41.0, range 25–61) Exclusions: incomplete audiometric or questionnaire data; apparent ear disease |
Continuous tinnitus: occurred practically always, steady-state character |
Hearing loss, worse ear Slight: > 20 dB, ≤ 40 dB at any freq 3–8 kHz; and ≤ 20 dB at 0.5, 1, 2 kHz Moderate: 41 dB–64 dB at any freq 3–8 kHz; and ≤ 20 dB at 0.5, 1, 2 kHz Severe: ≥ 65 dB at any freq 3–8 kHz; and ≤ 20 dB at 0.5, 1, 2 kHz Disabling: > 20 dB at any freq 0.5, 1, 2 kHz |
Christiansson and Wintzell (1993) Sweden, Nov 1986–Feb 1987 |
Cross-sectional 204 male infantry officers (entire unit) Providing training in use of small (rifles, machine guns) and heavy firearms (recoilless rifles, mortars) Exclusions: acute, chronic, secretory otitis |
Questionnaire: occurrence of tinnitus No information on persistence (no questions or definitions provided) |
Audiometric testing at 0.25 to 8 kHz |
Noise Exposure and Source of Exposure Data |
Prevalence of Tinnitus |
Prevalence of Tinnitus, by Hearing Level |
Comments |
Interview to determine previous noise exposure |
14% w/ tinnitus |
Normal hearing 3% w/ tinnitus Hearing loss 19% w/ tinnitus |
|
Questionnaire to establish exposure to weapons fire |
Continuous tinnitus: 9% Occasional tinnitus: 34% Correlations: Number of weapons impulses: r = 0.27, p < 0.001 Small-caliber weapons: r = 0.26, p < 0.001 Large-caliber weapons: r = 0.1, p < 0.005 Frequent use of hearing protectors: r = −0.17, p < 0.001 |
Normal hearing 2% continuous tinnitus 33% occasional tinnitus Slight/moderate loss 3% continuous 31% occasional Severe loss 20% continuous 32% occasional Disabling loss 26% continuous 43% occasional |
Data on other noise exposure may be incomplete |
Questionnaire on type of service, previous impulse noise exposure, use of hearing protectors Sound pressure levels for weapons measured at gunner’s ear and likely position of instructor |
17% w/ “annoyance of tinnitus” Ever exposed to heavy detonations: Yes: 26% w/ tinnitus No: 5% w/ tinnitus (X2, p < 0.001) Age (yrs) < 30 11% 31–40 19% 41–50 16% > 50 24% |
|
Possible recall bias in link between tinnitus and exposure to heavy detonations |
Study |
Design, Population |
Definition of Tinnitus |
Definition of Hearing Level or Hearing Loss |
d. Acoustic Trauma |
|||
Mrena et al. (2002) Finland, 1999 |
Longitudinal Former conscripts, Finnish Defense Forces 418 soldiers treated for acoustic trauma July 1984–April 1989, all w/ tinnitus 122 w/ persistent tinnitus at discharge, 1984–1989 101 reached in 1999 (83%), 66 still w/ tinnitus Mean age at exposure: 21 yrs (18.8–30.4) Age at follow-up 30–41 yrs Duration of tinnitus: 12 yrs (9.8–14.3) No prior tinnitus |
Tinnitus Handicap Questionnaire Rating scales for intensity, level of annoyance (0–100, least to most) |
Hearing loss: threshold > 20 dB HL at any frequency at discharge 6 cases w/ hearing loss on entering military service No indication of audiometric testing at follow-up |
Temmel et al. (1999) Austrian military service, Jan 1995–June 1996 |
Cross-sectional 81 male acoustic trauma patients Mean age: 22 yrs Treated 3 days after exposure Exclusions: hearing threshold > 20 dB HL at any frequency at start of service; illnesses, conditions that might affect auditory system |
No questions/ definition provided |
Acute acoustic trauma: acute acoustic exposure producing temporary or permanent pure-tone threshold shift Hearing loss: threshold > 20 dB HL Hearing thresholds at 0.125–8 kHz |
Noise Exposure and Source of Exposure Data |
Prevalence of Tinnitus |
Prevalence of Hearing Level Tinnitus, by |
Comments |
Assault rifle: 42 cases Bazooka: 3 cases Single cases: handguns, cannons, grenades 73% had fired the weapon 2 cases wore hearing protection (ear plugs) Other exposure history from medical records |
At discharge 29% (122 of 418) w/ tinnitus At follow-up (10–15 yrs) 66% (66 of 101) w/ tinnitus |
Normal hearing 4 cases (at time of discharge) Greater hearing impairment associated w/ greater tinnitus disturbance Perceived problems 33% tinnitus worse than hearing loss 33% hearing loss worse than tinnitus |
79% response (52 of 66) |
80% not wearing hearing protection (accidental discharges, loss of protectors, etc.) |
84% w/ tinnitus |
Hearing loss 83% w/ tinnitus No hearing loss 100% w/ tinnitus 75% had hearing loss at frequencies above 2 kHz |
No significant differences for: a. blank/live ammunition b. number of shots c. use of hearing protection |
Study |
Design, Population |
Definition of Tinnitus |
Definition of Hearing Level or Hearing Loss |
Man and Naggan (1981) Israel |
Cross-sectional 102 patients w/ acoustic trauma; 81 w/ tinnitus Age: 18–35 Selected for evidence of “cochlear trauma” (high-frequency hearing loss?) Exclusions: head injury, history of ear disease |
|
Audiometric testing, ISO calibration Worst threshold: 6 kHz for 76% Ears pooled |
Melinek et al. (1976) Israel, 1967–1970 |
Cross-sectional and longitudinal 433 soldiers treated for acute acoustic trauma 313 transferred to noncombat unit 120 continued in field units Inclusion criteria: Age 18 to 25 yrs; abrupt onset of tinnitus or hearing loss w/in 2 mos; audiometric grade of 2+ in at least one ear; diagnostic audiometry 1 wk or more after exposure; no history of prior industrial noise exposure; no history of ear disease; audiometric follow-up w/in 1 to 24 mos |
No definition provided |
Acute acoustic trauma: abrupt onset of symptoms (tinnitus or hearing loss) generally associated w/ unusually loud impact noise Severity grouping Normal: all thresholds except 8 kHz ≤ 15 dB Mild: thresholds 20–25 dB at 4 kHz and up to 30 dB or more at 6 kHz Moderate: thresholds ≥ 20 dB at 4 kHz w/ or w/out elevated thresholds at 3 kHz Severe: thresholds of ≥ 45 dB at 4 kHz w/ thresholds ≥ 35 dB at 2 kHz or thresholds of ≥ 25 dB at 1 kHz |
Noise Exposure and Source of Exposure Data |
Prevalence of Tinnitus |
Prevalence of Tinnitus, by Hearing Level |
Comments |
Questionnaire on noise exposure and complaints about hearing, tinnitus |
79% of subjects Always present: 70% (of ears) Sometimes present: 30% (of ears) Tinnitus matched at frequencies between 4 and 8 kHz (37% at 6; 23% at 4; 24% at 8) |
Higher intensity tinnitus associated w/ greater hearing loss (r = 0.71, p < 0.001) |
No statistical association between tinnitus level and disturbed sleep or concentration Potential selection effect from use of clinic population |
No ear protection used |
61% (of ears) w/ tinnitus Change in subjective symptoms (including tinnitus) at follow-up: Transferred Deterioration: 2% Improvement: 34% Continued field unit Deterioration: 15% Improvement: 22% |
Normal 42% Mild AT 60% Moderate AT 66% Severe 66% |
Some hearing loss may have existed before acoustic trauma Lower initial severity rating for group continuing in field units Statistical significance of differences not reported |
Noise Exposure and Source of Exposure Data |
Prevalence of Tinnitus |
Prevalence of Tinnitus, by Hearing Level |
Comments |
Noise levels measured under field conditions |
No overall prevalence reported |
Prevalence of tinnitus Normal: 15.7% I: 33% II: 25% III: 35% IV: 56% |
|
No estimate of rounds fired by individuals |
|||
|
|
Prevalence of tinnitus after firing Normal: 41% I: 49% II: 49% III: 57% IV: 64% |
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