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NIOSH study examines long hours
Working overtime is accepted by most industries as part of doing business. But a study by NIOSH (www.cdc.gov/niosh/docs/2004-143/) looks at the cost of long hours and overtime. Overtime in the United States has increased steadily from 1970 through the 1990s and, according to figures released in 2002 by the International Labour Office in Geneva, the annual number of hours worked per person in the United States is more than that in Japan and most of Western Europe, and is surpassed only by Thailand, Hong Kong, and South Korea.
The CDC report, "Overtime and Extended Work Shifts: Recent Findings on Illnesses, Injuries, and Health Behavior," examines 52 published studies that analyzed the relationship between long working hours and injuries, illnesses, health behaviors (alcohol use, smoking, physical activity, and body weight), and performance (muscular fatigue, cardiovascular fatigue, subjective alertness, car crashes, and cognitive functioning) in several fields of work, including health care, construction, manufacturing mining, public administration, transportation, and white-collar professions.
The studies revealed a pattern of deteriorating performance on psychophysiological tests as well as injuries in workers who put in long hours, especially those working very long shifts and those who combined 12-hour shifts with more than 40 hours total work per week.
Four studies found that during extended shifts, the ninth through 12th hours of work brought on feelings of decreased alertness, lower cognitive function, declined vigilance, and increased number of injuries. 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 pre-term 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.
Results were not all in agreement, NIOSH found. Some studies found no correlation between overtime or extended working hours and health or performance. Most found some link between working hours and at least one of the categories of health or performance.