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13 ARTICLE SUMMARIES* Reviewer: Susan Buchanan Title: Bruske-Hohlfeld, I., Mohner, M., Ahrens, W., Pohlabeln, H., Heinrich, J., Kreuzer, M., Jockel, K.H., and Wichmann, H.E. "Lung cancer risk in male workers occupationally exposed to diesel motor emissions in Germany." Am J Ind Med. 1999 Oct;36(4):40514. Abstract: Background: Although in several epidemiological studies exposure to diesel motor emis- sions (DME) shows an elevated lung cancer risk, it is still controversial whether DME is a human carcinogen. Methods: In a pooled analysis of two case-control studies on lung can- cer in Germany a total of 3,498 male cases with histologically or cytologically ascertained lung cancer and 3,541 male population controls were included. Information about lifelong occupational and smoking history was obtained by questionnaire. Drivers of lorries, buses, taxies, diesel locomotives and forklift trucks, bulldozers, graders, excavators, and tractors, were considered as exposed to DME and their cumulative exposure was estimated. All odds ratios were adjusted for smoking and asbestos exposure. Results: The evaluation of lung cancer risk for all jobs with DME-exposure combined showed an odds ratio of OR = 1.43 (95%-CI: 1.231.67). Most pronounced was the increase in lung cancer risk in heavy equip- ment operators (OR = 2.31 95%-CI: 1.443.70). The risk of tractor drivers increased with length of employment and reached statistical significance for exposures longer than 30 years (OR = 6.81, 95%-CI: 1.1739.51). The group of professional drivers (e.g., trucks, buses, and taxies), showed an increased risk only in West Germany (OR = 1.44, 95%-CI: 1. 181.76), but not in East Germany (OR = 0.83, 95%-CI: 0.601.14). DME-exposure in other traffic-related jobs (e.g., diesel engine locomotive drivers, switchmen, forklift opera- tors) was associated with an odds ratio of OR = 1.53 (95%-CI: 1.042.24). Conclusions: The study provides further evidence that occupational exposure to diesel motor emissions is associated with an increased lung cancer risk. Methodology: Two case-control studies were pooled for a joint analysis: all patients born in Germany after 1913 and diagnosed with lung cancer between 1988 and 1993 were used in one of the stud- ies. The other study evaluated residents in 4 regions of Germany who were diagnosed with lung cancer in 1994. Controls for both studies were selected at random from municipal reg- istries. A standardized questionnaire was performed in face-to-face interviews to obtain demographic information and job histories. Exposure to diesel motor exhaust was charac- terized by years of exposure after evaluating job task descriptions. Lung cancer risk was calculated according to the cumulated exposure and with respect to job group. Scope of Work: To estimate lung cancer risk in workers occupationally exposed to diesel motor exhaust. Sample Size: 3,498 cases and 3,541 controls Industry Sector: Professional drivers Major Limitations: Exposure was estimated based on participants' self-reported job task history. Findings Directly Related Working Conditions (Environmental except sleeper berth) to HOS (include page references): Odds ratios were adjusted for smoking and asbestos exposure and showed that professional drivers had significantly higher rates of lung cancer. Workers of any category who were exposed to diesel motor exhaust for between 20 and 30 years had significantly higher rates of lung cancer. Risk increased with increased duration of exposure. And compared with workers who had never been exposed, those who were exposed had a 43% higher rate of lung cancer. *Summaries are presented in the order submitted by the researchers.
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14 "Our study results show an increasing lung cancer risk for professional drivers, adjusted for smoking and asbestos exposure (Table III), which is similar to the results of most other epi- demiological studies." (p. 412) Reviewer's Notes: Though retrospective with estimated exposures, this study, with a large sample population, showed significant associations between lung cancer and both exposure to diesel exhaust and a dose-response.
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15 Reviewer: Susan Buchanan Title: Colt, J.S., Baris, D., Stewart, P., Schned, A.R., Heaney, J.A., Mott, L.A., Silverman, D., and Karagas, M. "Occupation and bladder cancer risk in a population-based case-control study in New Hampshire." Cancer Causes Control. 2004 Oct;15(8):75969. Abstract: Objective: To identify occupations with excess bladder cancer risk in New Hampshire, where bladder cancer mortality rates have been elevated for decades. Methods: Lifetime occupational histories were obtained from interviews with 424 cases and 645 controls in a population-based case-control study. Unconditional logistic regression models were used to estimate odds ratios (OR) and 95% confidence intervals (CI) for each occupation, adjusted for age and smoking. Analyses by duration of employment were carried out and interactions with smoking were examined. Results: Male tractor-trailer truck drivers had an elevated risk for bladder cancer (OR = 2.4, CI = 1.44.1), with a significant positive trend in risk with increasing duration of employment (P (trend) = 0.0003). Male metal/plastic pro- cessing machine operators also had a significant excess (OR = 4.9, CI = 1.615.1), attrib- utable mainly to molding/casting machine operators (OR = 16.6, CI = 2.1131). Elevated risk was also observed for male fabricators, assemblers, and hand workers (OR = 1.8, CI = 1.03.4). Women in certain sales occupations (sales clerks, counter clerks, and cashiers) had a significant excess risk (OR = 2.2, CI = 1.33.9) and a significant trend with duration of employment (P (trend) = 0.016), as did female health service workers (OR = 4.1, CI = 1.610.7; P (trend) = 0.014). There was a positive interaction between smoking and employment as a health service worker (p = 0.036). Conclusions: These findings are gen- erally consistent with previous studies. Elevated risks for male molding/casting machine operators, female sales workers, and female health service workers, especially those with a history of smoking, require further investigation. Methodology: This study is part of a larger population-based case-control study evaluating risk factors for bladder cancer in New Hampshire. This paper reports on the occupational data. New Hamp- shire residents diagnosed with bladder cancer between July 1994 and June 1998 were iden- tified from the state cancer registry. Controls were selected from the Department of Trans- portation population lists and matched for age and gender. Participants underwent a detailed in-home interview and information on job history was collected. Odds ratios were calcu- lated adjusting for age and smoking status. Scope of Work: To identify high-risk occupations in New Hampshire, where bladder cancer mortality rates have been elevated for decades, and to re-examine occupations that have been found to be associated with bladder cancer in previous studies. Sample Size: 424 cases, 645 controls Industry Sector: Tractor-trailer truck drivers Major Limitations: This study excludes cases which did not survive to the time of the interview, such as those with rapidly growing or late diagnosed cancers (e.g., most severe cases). This would be a positive bias if another factor produced a more aggressive picture than driving exposure and a negative bias if the reverse was true. Exposure duration had only 2 categories: employed as truck driver <5 years or 5 years. Findings Directly Related Driver Health (General) to HOS (include page references): Tractor-trailer truck drivers had an excess bladder cancer odds ratio of 2.3, which was sig- nificant. See Table 2. There was a positive trend of increasing risk with duration of employ- ment. See Table 3. Duration of employment was categorized by <5 year or 5 years. "In
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16 our study, bladder cancer risk was higher among men who drove trucks typically fueled by diesel (tractor-trailers) than among drivers of other types of trucks, and there was no increase for taxicab or bus drivers. Thus, our study supports the possibility of diesel expo- sure as the putative factor." (p. 765) Reviewer's Notes: This study was chosen from several that have shown significant odds ratios for bladder can- cer in truck drivers (see secondary references). Although the characterization of exposure was limited, it was the most recent study published on this issue. It showed both a positive association between truck driving and bladder cancer and a dose-response trend between drivers exposed 5 years compared with those with exposure for <5 years.
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17 Primary Reviewer: Susan Buchanan Complete Title: Guo, J., Kauppinen, T., Kyyronen, P., Heikkila, P., Lindbohm, M.L., and Pukkala, E. "Risk of esophageal, ovarian, testicular, kidney and bladder cancers and leukemia among Finnish work- ers exposed to diesel or gasoline engine exhaust." Int J Cancer. 2004 Aug 20;111(2):28692. Abstract: Occupational exposure to diesel exhaust has been classified as probably carcinogenic and occupational exposure to gasoline engine exhaust as possibly carcinogenic to humans. Ear- lier results concerning cancers other than lung cancer are scarce and inconsistent, and exposure-response relations have seldom been reported. We followed up a cohort of all eco- nomically active Finns born between 1906 and 1945 for 30 million person-years during 19711995. Incident cases of esophageal cancer (n = 2,198), ovarian cancer (5,082), testicu- lar cancer (387), kidney cancer (7,366), bladder cancer (8,110) and leukemia (4,562) were identified through a record linkage with the Finnish Cancer Registry. Occupations from the population census in 1970 were converted to exposures to diesel and gasoline engine exhausts with a job-exposure matrix (FINJEM). Cumulative exposure (CE) was calculated as product of prevalence, level and estimated duration of exposure. The relative risk of cancer for expo- sure categories in relation to the unexposed group was calculated using the Poisson regres- sion model and adjusted for confounders. An increasing relative risk for ovarian cancer was observed with the increasing CE of diesel exhaust (p for trend = 0.006). The relative risk in the highest CE category was 3.69 (95% CI = 1.389.86). For gasoline engine exhaust, the rel- ative risk was significantly increased only in the middle CE category (1.70; 95% CI = 1.112.62). Slight elevations of relative risk for bladder and kidney cancers were found at the lowest exposure level of engine exhausts, largely attributable to drivers. No effect of the expo- sures was observed for the other cancers. This study suggests an exposure-response relation between diesel exhaust and ovarian cancer. Copyright 2004 Wiley-Liss, Inc. Methodology: The study cohort comprised all economically active Finns born between 1906 and 1945. The incident cases of esophageal cancer, ovarian cancer, testicular cancer, kidney cancer, bladder cancer, and leukemia, diagnosed between 1971 and 1995 among persons born between 1906 and 1945 were extracted from the Finnish Cancer Registry. A job-exposure matrix was created on the basis of the census occupation and a national job-exposure matrix (FINJEM). The exposure estimates were based on exposure measurements, hazard surveys, and the judgments of 20 Finnish occupational hygienists. Since the exposure to diesel exhaust decreased in most occupations between 1945 and 1984, cumulative exposure was estimated for 5-year birth cohorts. Cumulative exposure to diesel exhaust was categorized into three categories: lowest, middle, and highest, in mg/m3-years. Risk ratios were con- trolled for cancer-specific confounding factors: socioeconomic status, cigarette smoking, alcohol consumption, body mass index (BMI), number of children (for women), and occu- pational exposure to ionizing radiation and aromatic hydrocarbon solvents. Scope of Work: To assess the risk of leukemia and cancers of the esophagus, ovary, testis, kidney and blad- der suspected to be associated with engine exhausts. Sample Size: 2,198 cases of esophageal cancer, 5,082 cases of ovarian cancer, 387 cases of testicular can- cer, 7,366 cases of kidney cancer, 8,110 cases of bladder cancer, and 4,562 cases of leukemia Industry Sector: Truck drivers; no further characterization Major Limitations: Exposure data not specific to individual cases Findings Directly Related Driver Health (General) to HOS (include page references): Standard incidence ratios of all six types of cancer in truck drivers were all greater than 1.0 and leukemia was statistically significant (Table II). Relative risks for cancers in occupations
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18 exposed to high, middle, or low levels of engine exhaust were significant for high cumula- tive exposure to diesel exhaust and ovarian cancer (Table III). Relative risks for high or mid- dle cumulative exposures were all insignificant for esophageal cancer, testicular cancer and leukemia. Kidney and bladder cancer were associated with low exposures. "Applying more sophisticated analysis to the same data, the present study revealed a positive exposure- response relation between ovarian cancer and diesel exhaust." (p. 290) "In the present study, we did not observe any positive exposure-response relations between engine exhausts and the other 5 cancers." (p. 290) Reviewer's Notes: This study addresses general causality as well as dose-response. Relative risks for all six types of cancer were greater than 1. Regarding dose-response, this was a negative study except for the interesting association between ovarian cancer and high cumulative exposure to diesel exhaust.
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19 Reviewer: Susan Buchanan CompleteTitle: Jansen, N., Kant, I., van Amelsvoort, L., Nijhuis, F., and van den Brandt, P. "Need for recovery from work: evaluating short-term effects of working hours, patterns and sched- ules." Ergonomics. 2003 Jun 10;46(7):66480. Abstract: In this paper working hours, patterns, and work schedules of employees were evaluated in terms of need for recovery from work. Self-administered questionnaire data from employ- ees of the Maastricht Cohort Study on Fatigue at Work (n = 12,095) were used. Poisson regression analyses and multivariate logistic regression analyses revealed that higher work- ing hours a day and working hours a week generally went together with more need for recovery from work. Overtime work was associated with higher need for recovery from work in both genders. Both male and female three-shift or irregular shift workers had higher odds of elevated need for recovery compared with day workers. When additionally control- ling for work-related factors, need for recovery levels among shift workers substantially low- ered. This study clearly showed that working hours and schedules are associated with need for recovery from work, with different associations for men and women. The associations between work schedules and need for recovery from work were very interrelated with other work-related factors. Future studies could further investigate the possibility that (a) shift work might function as a proxy of other work-related factors that explain the different lev- els in need for recovery from work or (b) job demands are perceived higher among shift workers and may therefore lead to more need for recovery from work. Methodology: Data from a baseline questionnaire from a large study on fatigue at work was used. Partic- ipants were employees of 45 different companies in The Netherlands. Three populations were studied: A. day employees only, B. day workers with vocation-level education only, and C. workers with 26 to 35 hr/wk of work, which would include those working on 5-shift systems. The Need for Recovery scale used was derived from the Dutch Experience and Assessment of Work questionnaire. The scale was derived using statements such as "I find it hard to relax at the end of a working day" and "My job causes me to feel rather exhausted at the end of a working day." Scope of Work: The present study was designed to describe the magnitude of associations between work- ing hours and need for recovery from work. Sample Size: Population A: 5170, Population B: 2167, Population C: 815 Industry Sector: n/a Major Limitations: No information on occupation. Healthy worker effect might be seen in workers who choose to work shifts. This would underestimate the effect. Findings Directly Related Recovery/Restart Periods to HOS (include page references): In men, continuous Need for Recovery scores were significantly associated with working more than 40 hr per week compared with fewer hours per week, working 9 to 10 hr per day compared with working fewer hours per day, and working overtime frequently. Working 25 hr per week was also significant. These results were controlled for age, disease, job characteristics of physical, emotional, and psychological demands. Using dichotomous out- come for Need for Recovery (highest quartile vs. lowest quartile), results in men showed significant associations between high need for recovery and working 9 to 10 hr per day, working more than 40 hr per week, and working frequent overtime. No dose-response analyses were performed. Regarding shift work, three-shift workers were significantly more likely to need recovery time from work than day workers.
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20 Author's conclusion: "The study showed that high working hours a day and high working hours a week generally went together with a higher need for recovery, confirming our hypothesis that day workers with many working hours a week report more need for recov- ery from work compared to employees working less hours a week. Extension of the work- ing day, in terms of overtime work, was particularly associated with more need for recov- ery in both men and women." (p. 674) Reviewer's Notes: This study, with a large sample, showed significant need for recovery from work in those working 9 to 10 hr a day, more than 40 hr per week, and overtime.
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21 Reviewer: Susan Buchanan Complete Title: Miyamoto, M., Shirai, Y., Nakayama, Y., Gembun, Y., and Kaneda, K. "An epidemio- logic study of occupational low back pain in truck drivers." J Nippon Med Sch. 2000 Jun;67(3):18690. Abstract: The factors involved in occupational LBP occurring in professional drivers were investi- gated epidemiologically with questionnaires (92 items) including LBP symptoms, personal factors and occupational factors. The responses of 153 of 181 truck drivers who work in a large chemical industry corporation were analyzed after they had completely filled in ques- tionnaires. As analysis of the results shows, the prevalence of LBP in 1 month of the sur- vey was 50.3%. Correlating among data of personal factors and LBP, the prevalence of LBP was significantly higher in the drivers (odds ratio of 2.7) who answered "yes" to the item "shortage of spending time with family" than in the drivers who did not answer yes. The occupational factors, working load and working environment showed no correlation with the prevalence of LBP. In contrast, 3 items of the working format related significantly to the prevalence of LBP: irregular duty time (odds ratio of 3.0), short resting time (2.4), and long driving time in a day (2.0). Eighty-one of the 153 drivers (52.9%) pointed out the rela- tionship between LBP and work, especially work which involves vibration or road shock. Our results and the results from previously published studies suggested that vibration is an obvious risk factor for LBP. From the viewpoint of prophylaxis, an improvement in work- ing conditions reduces the incidence of drivers' LBP to some extent. Methodology: Truck drivers who work for a large chemical industry corporation completed questionnaires. The questionnaire had 92 items with sections on LBP symptoms, personal factors, and occu- pational factors including working load, working environment, and working format. Scope of Work: To investigate by use of questionnaires, the prevalence of LBP symptoms and its risk fac- tors among truck drivers. Sample Size: 153 completed questionnaires Industry Sector: Truck drivers, no further characterization Major Limitations: No information on participant recruitment. Were they volunteers who might be more likely to have symptoms? No information was given on job types or exposures of participants. They all worked for the same company so one might not be able to generalize these results. Details on risk factors were lacking: what do irregular duty time and short resting time mean exactly? Self-reported symptoms of back pain may not indicate medical condition. Findings Directly Related Driver Health (General) to HOS (include page references): Lack of sleeping time was a risk factor for LBP but was not significant. Working load and working environment factors were not significant, although some associations were posi- tive. Two working format factors were significant: irregular duty time and short resting time. Insignificant but positive working format factors were long driving time in a day, long driving time in a week, long working time in a day, irregular meal time, and long working time in a week. (See Table 4, p. 189.) Reviewer's Notes: Despite the limitations noted above, this was a decent sized sample showing a significant relationship between LBP and irregular duty time and short resting time. Several other working format factors showed positive associations but were not significant. Overall this study suggests a relationship between driving hours in a day and LBP.
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22 Reviewer: Susan Buchanan Complete Title: Magnusson, M.L., Pope, M.H., Wilder, D.G., and Areskoug, B. "Are occupational drivers at an increased risk for developing musculoskeletal disorders?" Spine. 1996 Mar 15;21(6):7107. Abstract: Study Design: This study analyzed the role of exposure to driving and other covariates in reports of back, neck, and shoulder pain and resultant disability. Cohorts in Sweden and the United States were compared. Objectives: To establish the effect of mechanical and psy- chosocial factors in reporting back, neck, and shoulder pain and work loss. Summary of Background Data: There are numerous reports of a positive relationship between back pain and driving. However, exposure data are minimal. The influence of job satisfaction has not been assessed. Methods: The physical factors affecting reports of back, neck, and shoulder pain were investigated in a two-country cohort study of bus and truck drivers and sedentary workers. Vibration exposure was obtained by directly measuring the vibration imposed on the driver during a typical work day. Lifting exposure was attained by questionnaire. Cumu- lative exposure was computed based on work history. Musculoskeletal health information was based on a modified Nordic questionnaire, and other questionnaires recorded the phys- ical and psychosocial aspects of the work environment. Results: Of the sample, 50% reported LBP, with no difference between countries. The highest risk factors (odds ratios) for back and neck pain were long-term vibration exposure, heavy lifting, and frequent lift- ing. A combination of long-term vibration exposure and frequent lifting carried the highest risk of LBP. Work loss from LBP was influenced by perceived job stress. Conclusions: Vibration (resulting from driving) and lifting cause back, neck, and shoulder pain, whereas inability to work seems affected by stress at work. Methodology: Participants were recruited by personal contact with workers in several companies in Ver- mont and in Gothenburg, Sweden, who were male truck drivers or bus drivers. Sedentary workers served as the control group. Musculoskeletal health information was based on modified Nordic questionnaires (a standardized questionnaire used to assess musculo- skeletal symptoms.) Another questionnaire had detailed questions about the work environ- ment and the amount of lifting, sitting, standing, and driving on the job. Vibration levels during representative driving conditions were measured. The summed products of "aver- age acceleration" × "exposure duration" represented the daily vibration dose for that driver. Long-term vibration exposure was calculated as the product of daily exposure dose and years on the job as drivers. Scope of Work: To compare the effect of exposure to vibration on drivers' back, neck, and shoulder pain with those of control subjects in cohorts in two countries. Sample Size: U.S.: 124, Sweden: 241 Industry Sector: Bus drivers and truck drivers; no further detail given Major Limitations: Did not explain recruitment nor any detail on the participants. Did not measure awkward postures and seated exposure. Findings Directly Related Working Conditions (Environmental except sleeper berth) to HOS (include page references): "American truck drivers had a significantly higher daily exposure (to vibration) than bus drivers." (p. 9 of 16) "Those who reported LBP had a significantly higher total long-term vibration exposure than those who did not report LBP in those aged 35 to 45 years. Long- term exposure to vibration (equal to the vibration exposure over years in the profession)
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23 was the strongest predictor of length of sick leave because of LBP." (p. 9-10 of 16) "Sig- nificant single risk factors were . . . long-term vibration exposure." (p. 11 of 16) Reviewer's Notes: Because this study did not elaborate on sampling and recruiting methods, it is difficult to judge its validity; however, results show that long-term exposure to vibration was a signif- icant risk factor for LBP.
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38 Reviewer: Susan Buchanan Complete Title: Boffetta, P. and Silverman, D.T. "A meta-analysis of bladder cancer and diesel exhaust exposure." Epidemiology. 2001 Jan;12(1):12530. Abstract: The aim of this study is to review and summarize the available epidemiologic studies of bladder cancer and occupational exposure to diesel exhaust. We retrieved relevant studies and abstracted their characteristics and results. We assessed the heterogeneity of the results to decide whether to perform a fixed-effects model meta-analysis. We identified 35 relevant studies. No overall meta-analysis was performed because of heterogeneity in results. Results of railroad workers (N = 14) suggested an increased occurrence of bladder cancer, but we did not conduct a meta-analysis. The summary relative risk (RR) among truck driv- ers was 1.17 (95% CI = 1.061.29, 15 studies) and that among bus drivers was 1.33 (95% CI = 1.221.45, 10 studies). Ten studies considered diesel exhaust exposure based on a job exposure matrix or a similar approach; the summary relative risk for these studies was 1.13 (95% CI = 1.001.27). A positive dose-response relationship was suggested by 10 of the 12 studies that provided relevant information. The summary relative risk for high diesel exposure was 1.44 (95% CI = 1.181.76). There was some evidence of publication bias, however, with a lack of small studies with null or negative results. Our review suggests that exposure to diesel exhaust may increase the occurrence of bladder cancer, but the effects of misclassification, publication bias, and confounding cannot be fully taken into account. Methodology: Searched epidemiologic literature for studies on cancer after exposure to diesel exhaust and for studies on occupational risk factors for bladder cancer. Concentrated on 5 occupational groups including truck drivers. Scope of Work: To summarize available results of epidemiologic studies of the association between occu- pational exposure to diesel exhaust and occurrence of urinary bladder cancer. Sample Size: 29 studies on bladder cancer and exposure to diesel exhaust Industry Sector: Truck drivers, no further characterization Major Limitations: Findings Directly Related Working Conditions (Environmental except sleeper berth) to HOS (include page references): Fifteen results were available for truck drivers. Exposure was characterized by either years of employment or job exposure matrix. For exposure to diesel exhaust characterized as "high," relative risk was 1.44 and significant. For "any exposure," relative risk was 1.23 and significant. See Table 5. "Out of 12 results for `heavy exposure,' 10 were higher than their corresponding results for `any exposure,' and only one of the remaining was lower." (p. 129) Reviewer's Notes: Meta-analysis showing positive evidence for increased risk of bladder cancer among truck drivers with "any exposure" to diesel exhaust. Truck drivers with "high" exposure were sig- nificantly more likely to have bladder cancer than those with lower levels of exposure.
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39 Reviewer: Susan Buchanan Complete Title: Lings, S. and Leboeuf-Yde, C. "Whole-body vibration and low back pain: a systematic, crit- ical review of the epidemiological literature 19921999." Int Arch Occup Environ Health (2000);73: 290297. Abstract: Objectives: A previous extensive review of the literature including that from the middle of 1992 concluded that WBVs may contribute to low back pain, but that the exposure-response relationship had not been clarified. We reviewed the literature of the past 7 years to find out: (i) whether there is evidence in the recent epidemiological literature for a causal associa- tion between WBV and LBP, and (ii) if there is evidence in the recent literature for a dose- response relationship between WBV and LBP. Methods: All relevant epidemiological arti- cles, which were obtained through a search in the databases MEDLINE, OSH-ROM, and TOXLINE, and through personal communication, were reviewed independently by the two authors, using a checklist. Results: Twenty-four original articles concerning the association between WBV and the lower back were retained for use. Only seven articles passed our pre- determined quality criteria. Of the seven reports, one showed increased frequency of lum- bar prolapse in occupational drivers, and six showed LBP to be more frequent in WBV- exposed groups. Only two of the four articles reporting on dose showed a dose-response association. Conclusions: Despite the lack of definite evidence, we found sufficient reasons for the reduction of WBV-exposure to the lowest possible level. If new knowledge is to be produced, good prospective studies with repeated measurements of exposure, analyses of work postures, and clear definitions and subgroupings of LBP are needed. Other research in this field should be given up, and the resources used for more important issues, as the size of the problem of WBV is probably on the decrease because of the technical prophy- lactic developments that are already in progress. Methodology: Literature review of MEDLINE, OSH-ROM, and TOXLINE of all original epidemiologi- cal articles published from 1992-1999. They were reviewed by the two authors, indepen- dently using predetermined quality criteria. Scope of Work: To conduct a review of the literature on WBV and LBP since the issue was last reviewed in 1992. Questions addressed were: Is there evidence for a definite association between WBV and LBP? Is there evidence for a dose-response relationship between WBV and LBP? Sample Size: 24 original reports were identified: 21 passed initial screening, 7 studies fulfilled at least 5 of the 6 quality criteria. Industry Sector: Various Major Limitations: Authors seemed a little opinionated, may have had an agenda Findings Directly Related Working Conditions (Environmental except sleeper berth) to HOS (include page references): Six reports showed LBP to be more frequent in study groups and one showed increased fre- quency of hospitalization for disc herniation in drivers. Of the four studies on dose-response, two showed an association. ". . . despite at least 24 epidemiological publications address- ing the question, the evidence still remains weak." (p. 291) Authors' conclusion: "The six reports that best fulfilled our quality criteria were predomi- nantly in favour of a positive association between WBA and LBP . . . Hence it can still be concluded that here is probably an association between WBV and LBP," ( but not causal-
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40 ity) "Existing knowledge yields sufficient reasons for reducing exposure to the lowest pos- sible level." (p. 296) Reviewer's Notes: Although the authors give mixed conclusions about the effect of WBV on LBP, most of the studies included in the literature review found positive associations. However, evidence for dose-response was weak.
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41 Reviewer: Peter Orris Complete Title: Jensen, Marianne V. Tuchsen, F., and Orhede, E. "Prolapsed Cervical Intervertebral Disc in Male Professional Drivers in Denmark, 19811990: A Longitudinal Study of Hospital- izations." Spine 1996, October 21(20): 23522355. Abstract: Study Design: This study of professional drivers is a part of a longitudinal record linkage study of all economically active men in Denmark, identified on January 1, 1981. Informa- tion about the main occupation was identified in 1980. The cohort was followed for first hospitalization with prolapsed cervical intervertebral disc until December 31, 1990. Objec- tives: To examine the risk of prolapsed cervical intervertebral disc in all Danish professional drivers, and to analyze exposures of the male drivers in a sample of all Danish male drivers. Methods: A standardized hospitalization ratio was calculated for each subgroup of drivers using all economically active people as the standard. Additional exposure information was extracted from a national survey on work environment. Almost all men in occupations involving professional driving had a statistically significant elevated risk of being hospi- talized with prolapsed cervical intervertebral disc. Conclusions: Professional driving is a risk factor for prolapsed cervical intervertebral disc. Methodology: Methods: This study of professional drivers is a part of a longitudinal record linkage study of all economically active men in Denmark, identified on January 1, 1981. Information about the main occupation was identified in 1980. The cohort was followed for first hospi- talization with prolapsed cervical intervertebral disc until December 31, 1990. A standard- ized hospitalization ratio was calculated for each subgroup of drivers using all economi- cally active people as the standard. Additional exposure information was extracted from a national survey on work environment. Scope of Work: Only a few studies on occupation and prolapsed cervical intervertebral disc have been pub- lished. These studies suggest that professional driving may be a risk factor for development of prolapsed cervical intervertebral disc. Drivers are exposed to WBVs, heavy lifting, and a sedentary position. Other potential exposures are accelerations and decelerations and whiplash accidents. Such exposures may be involved in the causation of prolapsed cervical intervertebral disc. Sample Size: 1.3 million economically active men in Denmark Industry Sector: Various Major Limitations: Unable to separate WBV from other musculoskeletal stressors on drivers Findings Directly Related Driver Health (General) to HOS (include page references): Almost all men in occupations involving professional driving had a statistically significant elevated risk of being hospitalized with prolapsed cervical intervertebral disc. Reviewer's Notes: An objective prospective study identifying professional driving as a risk factor for the development of prolapse of a cervical intervertebral disc.
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42 Reviewer: Susan Buchanan Complete Title: Gustavsson, P., Plato, N., Hallqvist, J., Hogstedt, C., Lewne, M., Reuterwall, C., and Scheele, P. "A population-based case-referent study of myocardial infarction and occupa- tional exposure to motor exhaust, other combustion products, organic solvents, lead, and dynamite. Stockholm Heart Epidemiology Program (SHEEP) Study Group." Epidemiol- ogy. 2001 Mar;12(2):2228. Abstract: This case-control study investigated the risk of MI from occupational exposure to motor exhaust and other combustion products. We identified first-time, nonfatal MIs among men and women 45 to 70 years of age in Stockholm County from 1992 through 1994. We selected referent subjects from the population to match the demographic characteristics of the cases. A lifetime history of occupations was obtained by questionnaire. The response rate was 81% for the cases and 74% for the referents, with 1,335 cases and 1,658 referents included in the study. An occupational hygienist assessed occupational exposures, coding the intensity and probability of exposure for each subject. We adjusted relative risk esti- mates for tobacco smoking, alcohol drinking, hypertension, diabetes mellitus (DM), being overweight, and physical inactivity at leisure time. The relative risk of MI was 2.11 (95% CI = 1.233.60) among those who were highly exposed and 1.42 (95% CI = 1.051.92) among those who were intermediately exposed to combustion products from organic mate- rial. We observed an exposure-response pattern, in terms of both maximum exposure inten- sity and cumulative dose. Exposure to dynamite and organic solvents was possibly associ- ated with an increased risk. The other exposures were not consistently associated with MI. Methodology: Case-control study of first-time MI. Cases were identified from intensive care units in Stockholm County. Controls were selected from a computerized population register and were matched according to sex, age, and hospital catchment area. Subjects completed ques- tionnaires on occupational history. A job exposure matrix was created by industrial hygien- ists using unpublished and published occupational hygiene reports, personal contacts and professional experience to quantify intensity of exposure using estimated exposure preva- lence within each occupation (in terms of annual average of 8-hr work day exposures to motor exhaust.) Relative risks were adjusted for smoking, alcohol intake, hypertension, weight, DM, and physical inactivity. Scope of Work: To investigate the risk of MI from occupational exposure to motor exhaust and other com- bustion products. Sample Size: 1,335 case and 1,658 controls Industry Sector: Did not specify Major Limitations: Those who survived MI were interviewed. Those not surviving were excluded (history of exposure not taken from surviving family members). Exposures to exhaust were estimated, not measured. Did not control for cholesterol results. Did not specify type of exhaust. Findings Directly Related Working Conditions (Environmental except sleeper berth) to HOS (include page references): (Actual journal page numbers are not given in this on-line document.) Working conditions: There was a non-significant elevation of relative risk of MI with moderate exposure to motor exhaust. No dose response trend was seen. There was a significantly increased rela- tive risk of MI with high or intermediate exposure to combustion products, (besides motor
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43 exhaust). The same results were found when cumulative exposure was estimated. (See Tables 2 and 4.) "We found some indications of an increased risk of MI in association with exposure to motor exhaust, but no firm evidence of an exposure-response relation." Reviewer's Notes: The results are suggestive of increasing MI risk with cumulative exposure to motor exhaust.
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44 Reviewer: Susan Buchanan Complete Title: Chen, J.C., Dennerlein, J.T., Shih, T.S., Chen, C.J., Cheng, Y., Chang, W.P., Ryan, L.M., and Christiani, D.C. "Knee pain and driving duration: a secondary analysis of the Taxi Driv- ers' Health Study." Am J Public Health. 2004 Apr;94(4):57581. Abstract: Objectives: We explored a postulated association between daily driving time and knee pain. Methods: We used data from the Taxi Drivers' Health Study to estimate 1-year prevalence of knee pain as assessed by the Nordic musculoskeletal questionnaire. Results: Among 1,242 drivers, the prevalence of knee pain, stratified by duration of daily driving (6, >6 through 8, >8 through 10, and >10 hr), was 11%, 17%, 19%, and 22%, respectively. Compared with driving 6 or fewer hr per day, the odds ratio of knee pain prevalence for driv- ing more than 6 hr per day was 2.52 (95% CI = 1.364.65) after adjustment for socioeco- nomic, work-related, and personal factors in the multiple logistic regression. Conclusions: The dose-related association between driving duration and knee pain raises concerns about work-related knee joint disorders among professional drivers. Methodology: Taxi drivers in Taipei city were recruited during free government physical exams. Ques- tionnaires were completed which included information on daily driving hours, among other work factors, and presence of knee pain in the previous 12 months. Scope of Work: To test the hypothesis that prolonged driving is associated with increased knee pain among taxi drivers. Sample Size: 1,242 taxi drivers (of at least 1 years' duration) Industry Sector: Taxi drivers Major Limitations: Used self-reports of knee pain. Presence of pain does not necessarily indicate a medical condition. Findings Directly Related Shifts/Time of Day/Circadian to HOS (include page references): Workers with >10 hr of daily driving had significantly increased risk of knee pain. There was a dose response in history of knee pain and daily driving times of 6 hr, 6 to 8 hr, 8 to 10 hr, and >10 hr (all significant) when controlled for age, gender, BMI, income, other demographics, and physical exertion during work and leisure time, and professional senior- ity. No associations were found between knee pain and vehicle manufacturers or engine sizes. Authors' conclusion: "Our exploratory analyses of the TDHS (Taxi Drivers' Health Study) baseline data revealed a strong and robust association between long driving times and knee pain. The public health impact of work-related knee pain among professional driv- ers could be substantial." Reviewer's Notes: Agree with previous quote.
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45 Reviewer: Susan Buchanan Complete Title: Barton, J. and Folkard, S. "Advancing Versus Delaying Shift Systems." Ergonomics 1993;36(1-3):5964. Abstract: Two-hundred sixty-one shift workers from a range of UK industrial and service organiza- tions took part in a study to determine the impact of the direction of shift rotation on the health and well-being of the individuals concerned. All the systems were continuous, rotat- ing over three shifts. Systems were classified according to whether they delayed (i.e., rotated in a forward direction) or advanced (i.e., rotated in a backward direction). In addi- tion, advancing systems were divided into those which incorporated a quick return (i.e., a break of only 8 hr when changing from one shift to another) and those which did not. The results add some support for the use of delaying as opposed to advancing systems, and high- light the detrimental affects of incorporating a quick return into an advancing system. Methodology: All subjects completed the Standard Shift Work Index. ANCOVA was performed to deter- mine the effect of the direction of shift rotation on each outcome measure. Scope of Work: To examine the relative effect of advancing or delaying systems on shift workers. Sample Size: A total of 261 industrial and service shift workers from a range of occupations took part in the study Industry Sector: Shift workers from steel industry, power industry, post office, police force, and air traffic control officers Major Limitations: There was no information given on the sampling method, whether the participants were vol- untary or randomly selected. Findings Directly Related Shifts/Time of Day/Circadian to HOS (include page references): Compared with the delayed rotating shift system, workers on the advancing system were significantly more likely to complain of digestive and cardiovascular disorders, chronic fatigue, and cognitive anxiety. (See Table 1, p. 61.) "Comparing advancing systems with and without a quick return produced few significant differences, yet overall, it was the former who reported poorer physical health." (p. 63) "In conclusion it would appear that the critical feature may not be related entirely to the direction of rotation but to a combination of direction and the length of break when chang- ing from one shift to another." (p. 64) Reviewer's Notes: This article adds to the body of literature associating a change in sleep schedule (a.k.a. cir- cadian rhythm) with GI and cardiovascular effects.
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46 Reviewer: Susan Buchanan Complete Title: Morgan, L., Arendt, J., Owens, D., et al. "Effects of the endogenous clock and sleep time on melatonin, insulin, glucose and lipid metabolism." J Endocrin 1998;157:443451. Abstract: This study was undertaken to determine whether the internal clock contributes to the hor- mone and metabolic responses following food, in an experiment designed to dissociate internal clock effects from other factors. Nine female subjects participated. They lived indoors for 31 days with normal time cues, including the natural light and darkness cycles. For 7 days they retired to bed from 0000 to 0800. They then underwent a 26-hr `constant routine' (CR) starting at 0800 h, being seated awake in dim light with hourly 88 Kcal drinks. They then lived on an imposed 27-hr day for a total of 27 days. A second 26-hr CR, start- ing at 22 hr was completed. During each CR salivary melatonin and plasma glucose, triglyc- eride (TAG), non-essential fatty acids (NEFA), insulin, gastric inhibitory peptide (GIP) and glucagons-like peptide-1 (GLP-1) were measured hourly. Melatonin and body temperature data indicated no shift in the endogenous clock during the 27-hr imposed schedule. Post- prandial NEFA, GIP and GLP-1 showed no consistent effects. Glucose, TAG, and insulin increased during the night in the first CR. There was a significant effect of both the endoge- nous clock and sleep for glucose and TAG, but not for insulin. These findings may be rel- evant to the known increased risk of cardiovascular disease amongst shift workers. Methodology: Subjects were observed for 31 days and were required to live on an imposed 27-hr day cycle. Activity was monitored with wrist monitors and rectal temps were recorded. Blood levels for triacylglycerol, insulin, and glucagon-like peptide. Salivary melatonin was measured. Scope of Work: To determine to what extent the internal clock contributes to the hormonal and metabolic responses following a meal. Sample Size: 9 female undergraduates Industry Sector: n/a Major Limitations: Testing was performed in experimental conditions which might not reflect real life scenarios. Findings Directly Related Shifts/Time of Day/Circadian to HOS (include page references): "Dissociation of the internal clock and sleep in the second constant routine leads to a dampening of the peak response to glucose and the appearance of two comparable peaks, suggesting a `spreading' of glucose intolerance such that it occurs at two periods of the day." (p. 448449) "The present study has shown for the first time that the length of wake- fulness also has an effect on glucose tolerance, independent of any circadian rhythm or sleep itself." (p. 449) Reviewer's Notes: This group previously reported that immediately after a simulated 9-hr advance, such as might be found in rotating shift work, postprandial insulin and glucose responses to a stan- dard mixed meal were significantly greater than to the same meal at the same external clock time before the phase shift. The changes were suggestive of insulin resistance, a risk factor for cardiovascular disease. This study takes this issue a step further and tries to separate out the possible effect of a cir- cadian rhythm change. Results showed that insulin resistance indeed worsened with a longer sleep-wake cycle but was independent of changes in the internal clock or circadian rhythm.
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47 Reviewer: Susan Buchanan Complete Title: Scott, A. "Shift Work and Health." Primary Care Dec 2000;27(4):10571078. Abstract: Night work and rotating shift work disrupt the circadian timing system. This disruption may produce significant deleterious symptoms in some workers. Certain medical conditions may be aggravated by shift-work scheduling, and shift workers are at increased risk of experi- encing cardiovascular, GI, and reproductive dysfunction. Vulnerable individuals may develop clinical depression when working shifts. Primary care practitioners may intervene by providing medical surveillance and education programs for shift-working patients and their families. Methodology: Written as a chapter with 166 references. It is not original research but is an excellent review of the current literature up to 2000. Scope of Work: This is a chapter on Occupational and Environmental Medicine in a hard bound journal. It offers an overview of circadian rhythms and the health effects of night work and sleep depri- vation, and offers a review of specific medical disorders associated with shift work. Sample Size: n/a Industry Sector: n/a Major Limitations: This is not original research. It assumes validity of its references. Findings Directly Related Shifts/Time of Day/Circadian: to HOS (include page references): Circadian rhythm: ". . . each time the work schedule rotates, for a period of time after the time shift, the circadian system will be in a desynchronized state." (p. 1059) Shift-work intolerance: "Up to 20% of shift workers may have a disproportionate number of symptoms of illness when assigned to chronobiologically poorly designed shift-work schedules involving night work." (p. 1061) "Specific factors that affect shift work tolerance include: . . . rotating or fixed, number of nights worked consecutively, frequency of week- ends off, length of shift and starting time, overtime requirements, predictability of sched- ule." (p. 1061) GI Disorders: "Gastrointestinal dysfunction is common in shift workers. . . . Some studies have not found an increased incidence of peptic ulcer disease in shift workers, but the majority of studies addressing this outcome have. Including non-English reports, 16 of 24 studies evaluating PUD and shift work found shift workers to be at greater risk of devel- oping PUD than day workers. . . . Circadian rhythm disruption also contributes to shift- work related GI dysfunction." (p. 1062) Cardiovascular morbidity: "Although there are studies that have not found changes in lipid profiles related to shift work, a recent thorough review of this research concluded that the better studies do indicate that shift workers have somewhat higher levels of cholesterol as well as triglycerides." "Although early studies concluded shift work was not associated with an increase in CVD, most of the more recent, better epidemiologically designed studies have found an increased risk of CVD." (p. 1063) Reproductive Health: Studies quoted showed shift work and rotating shift work to be asso- ciated with higher prematurity rate, low birth weight, spontaneous abortion, and decreased fertility rate." (p. 1064-65)
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48 Exacerbation of Medical Disorders: "Shift work also may aggravate certain medical disorders related to circadian rhythm disruption, psychosocial stress, or sleep deprivation. Conditions that may be exacerbated or aggravated by irregular schedules or night work and are therefore potential contraindications for shift work include: GI disorders, DM, epilepsy, cardiovascu- lar disease, psychiatric disorders, sleep disorders, reproductive dysfunction." (p. 1066) Reviewer's Notes: This chapter, with 166 references, confirms the multiple health issues related to shift work and rotating shift work including GI, cardiovascular, and reproductive health.