OVERTIME

Overtime was associated with poorer perceived general health, increased injury rates, more illnesses, or increased mortality in 16 of 22 studies. One meta-analysis of long work hours suggested a possible weak relationship with preterm birth. Overtime was associated with unhealthy weight gain in two studies, increased alcohol use in two of three studies, increased smoking in one of two studies, and poorer neuropsychological test performance in one study. Some reports did not support this trend, finding no relationship between long work hours and leisure-time physical activity in two of three studies and no relationship with drug abuse in one study.

EXTENDED WORK SHIFTS

A pattern of deteriorating performance on psychophysiological tests and injuries while working long hours was observed across study findings, particularly in very long shifts and when 12-hour shifts were combined with more than 40 hours of work a week. Four studies reported that the 9th to 12th hours of work were associated with feelings of decreased alertness and increased fatigue, lower cognitive function, declines in vigilance on task measures, or increased injuries. Effects after the 12th hour of work were not examined. Two studies examining physicians working very long shifts reported deterioration in various measures of cognitive performance.

When 12-hour shifts were combined with other work-related demands, a pattern of more adverse findings was detected across studies. Six studies, examining 12-hour shifts combined with more than 40 hours of work per week, reported increases in health complaints, deterioration in performance, or slower pace of work. Two studies that compared 8- and 12-hour schedules during day and night shifts reported that 12-hour night shifts were associated with more fatigue, smoking, or alcohol use. Two studies examining start times for 12-hour shifts reported that decrements in alertness or more health complaints were associated with early 6:00 a.m. start times. One study examining 12-hour shifts in hot work environments also reported a slower pace of work as compared to shorter shifts. Another study examining high workloads during 12-hour shifts showed increased discomfort and deterioration in performance as compared to shorter shifts.

More definitive statements about differences between 8-hour and 12-hour shifts are difficult due to the inconsistencies in work schedules examined across studies. Work schedules differed by the time of day (i.e., day, evening, night), fixed versus rotating schedules, speed of rotation, direction of rotation, number of hours worked per week, number of consecutive days worked, and number of rest days on weekends. All of these factors can influence how overtime relates to health and safety. In addition, some studies of extended work shifts did not report how many hours participants worked per week or other details about their work schedules, which may have accounted for the findings. Also, some studies reported findings for groups of workers working mixed directional shift rotations and varying numbers of hours per week, details which complicated an assessment of the results.

OTHER WORK SCHEDULE CHARACTERISTICS

Few studies examined the combined influence of shift work and overtime on health. The laboratory study by Rosa et al. [1998] reported that four 12-hour night shifts per week were associated with the highest upper extremity muscle fatigue as compared to five 8-hour days and four 12-hour days. Trinkoff and Storr [1998] reported that nurses on extended night or extended rotating shifts were at increased odds for alcohol use and that extended night shifts increased the odds for smoking.

Some findings indicated that worker ability to exert control over work schedules may have influenced outcomes. For example, Smith et al. [1998] reported that 12-hour shifts having some flexibility in start times were associated with more favorable sleep quality, psychological wellbeing, and alertness, as compared with rigid schedules. One of the 52 summarized studies directly examined the influence of mandated or involuntary overtime. The combined influence of high pressure to work overtime and low rewards was associated by van der Hulst and Geurts [2001] with an increased risk for somatic complaints, poor recovery, burnout, and negative work-home interference. Previously published reviews of the literature did not address the influence of mandated overtime on health and safety [Rosa 1995; Sparks et al. 1997; Spurgeon et al. 1997]. Golden and Jorgensen [2002], however, cautioned that the mandated nature of overtime may limit the worker’s ability to plan for sleep and recuperation, and to arrange for child care and other family responsibilities. As a result, health and safety effects associated with mandated versus voluntary overtime may differ.

COMPENSATION, VACATION TIME, COMMUTE TIME

Siu and Donald [1995] and van der Hulst and Geurts [2001] suggested that compensation may reduce adverse effects. In addition, Nakano et al. [1998] indicated that economic conditions (prosperity as compared with recession or depression) may influence the relationship between pay, overtime, and health and safety. Few studies, however, systematically examined how compensation influenced the relationship between long work hours and health and safety.

Length of vacation and commute time may also influence associations of overtime with health and safety. Higher numbers of annual leave days may allow more rest and may reduce the impact of overtime. Also, commute time to work may add to the job strain and may influence associations with overtime. Few studies have examined the influence of vacation time or commute time on long work hours and health.

GENDER AND AGE

Studies have given more attention to male workers than to female workers and less is known about how overtime and extended work shifts influence health and safety in women. Statistics Canada [2000] reported that women tend to spend more of their time away from work on child care and domestic responsibilities, which may reduce the time available for sleep and recovery from work. The study by Fredriksson et al. [1999] provided some support for increased risk for musculoskeletal disorders when long hours worked combined with additional domestic workload.

Another consideration is the influence of long work hours on reproductive outcomes. One metaanalysis reported a possible weak relationship between overtime and preterm births, and another study reported an association between long work hours and subfecundity [Mozurkewich et al. 2000; Tuntiseranee et al. 1998]. Few studies have examined the influence of overtime and extended work shifts in pregnant women, or prenatal and neonatal mortality and morbidity, as well as fertility rates.

One laboratory study examining the influence of age on extended work shifts reported that younger participants maintained better performance across extended work shifts when compared with older participants [Reid and Dawson 2001]. However, few studies have examined the effect of worker age on performance or health and safety in real-work environments. In addition, little is known about the way various work tasks and other work-related factors influence the relationship with age.

CHRONIC HEALTH PROBLEMS

Studies of long working hours have examined healthy workers for the risk of contracting an acute myocardial infarction, diabetes mellitus, hypertension, subfecundity, and preterm birth. Little data, however, are available about symptom management and disease progression in workers with pre-existing chronic conditions. According to Yelin et al. [1999], the 1992 data from the U.S. Health and Retirement Survey indicated that 83% of all persons aged 51 to 61 years live with a self-reported chronic condition.

OCCUPATIONAL EXPOSURES

Two of the 52 summarized reports addressed occupational exposures (i.e., chemical, heat, noise, lifting) in conjunction with overtime and extended work shifts. Mizoue et al. [2001] reported that overtime was associated with more sick building syndrome symptoms, and Brake and Bates [2001] found that miners working long shifts in hot environments paced themselves, thus, reducing their effort. Little has been reported on other occupational exposures. Extended work shifts and overtime lengthen exposure times and shorten recovery times, and the health consequences are uncertain.

Index: Main Page Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Table 8 Table 9 Abbreviations Acknowledgments Introduction Description of Work Schedules and Samples Health and Safety Findings Summary Concluding Remarks References