Meijman, 1987), reduced motivation, and decreased vigor for successful completion of required tasks (Gravenstein et al., 1990). Thus, fatigue also causes decreased productivity. Tired workers accomplish less, especially if their tasks demand accuracy (Krueger, 1994; Rosa and Colligan, 1988). In nurses’ work environments, fatigue is produced by shift work and extended work hours.

Shift Work

Since almost all physiological and behavioral functions are affected by circadian rhythms, the time of day when work must be completed is important. The human circadian rhythm strongly favors sleeping during nighttime hours. Overall capacity for physical work is reduced at night (Cabri et al., 1988; Cohen and Muehl, 1977; Rosa, 2001; Wojtczak-Jaroszowa and Banaszkiewicz, 1974). Reaction times, visual search, perceptual–motor tracking, and short-term memory are worse at night than during the day (Folkard, 1996; Monk, 1990). On-the-job performance also deteriorates. At night, railroad signal and meter reading errors increase, minor errors occur more frequently in hospitals, and switchboard operators take longer to respond to phone calls (Monk et al., 1996).

Night shift workers also have difficulty staying awake. In a survey of nurses working in seven West Coast hospitals, 19.3 percent of those working night and rotating shifts reported struggling to stay awake at least once during the previous month while taking care of patients, compared with 3.8 percent of day and evening shift nurses (Lee, 1992). In a 1986 study of nurses in one hospital, 35.3 percent of those who routinely rotated to the night shift, 32.4 percent of those who always worked nights, and 20.7 percent of day/evening shift nurses who worked occasional nights reported falling asleep during the night shift at least once a week. Nurses working night shifts or rotating shifts also made more on-the-job procedural and medication errors due to sleepiness than did nurses working other shifts. Sleepiness appeared to be confined to the night shift, as none of the shift rotators or day/evening nurses who worked occasional nights reported significant difficulties remaining alert on other shifts (Gold et al., 1992). Likewise, objective findings of sleeping on duty were reported in a study of 15 French nurses working at night. Only 4 of the 15 were able to remain awake all night while at work as measured by activity (wrist actigraphy) and sleep (polysomnographic) recordings; the remaining nurses averaged 86.5 (standard deviation ± 77.6) minutes of sleep while on duty (Delafosse et al., 2000). Difficulties in maintaining alertness at night are not confined to nurses. Self-reported and objective measures of sleep were recorded in U.S. Air Force traffic controllers on duty at night (Luna et al., 1997). And the most consistent factor influencing truck driver fatigue and alertness over a

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