Long hours may lead to injuries, poor health

NIOSH reviews studies on work schedule

Long hours and overtime are linked to higher injury rates, more frequent illnesses, and even increased mortality, according to a review of 52 published research reports by the National Institute for Occupational Safety and Health (NIOSH).

The health effects were magnified when shifts of 12 hours or longer were combined with a work week of more than 40 hours. For example, two studies of physicians who worked very long shifts reported a decline in cognitive performance.1 Although the review was not limited to health care, 19 of the studies were conducted in the health care arena.

This NIOSH review adds to the findings of a 2003 Institute of Medicine report, which recommended restricting nurses from working more than 12 hours at time or more than 60 hours in a week to prevent "error-producing fatigue." While the IOM focused on patient safety, the NIOSH study relates overtime and long hours to worker health.

The relationship between work schedule and worker health is a complex one, says Claire Caruso, PhD, RN, a NIOSH research health scientist based in Cincinnati and an author of the report. "When you have a combination of several demanding work characteristics together, it seemed to produce more consistently negative outcomes," she says.

For example, working night shift or rotating shifts adds to the burden if someone also had long shifts with mandatory overtime, adds Caruso. "There’s an issue about the pattern of workdays to rest days. Are you working seven 12-hour shifts in a row and then you’ve got four days off . . . or are there interspersed short runs of workdays?"

Having time to rest improves function and health outcomes, she says. Yet researchers still have much to learn about how longer shifts affect worker health, she says.

One study linked shifts of 12 or more hours to increased risk of back disorders for nurses, compared with those who worked an 8-hour shift. The combination of 12-hour shifts and 40 or more hours of work per week also was associated with greater risk for neck, shoulder, and back disorders compared with nurses who worked five 8-hour days.2

"Are 8-hour shifts better, or are 12-hour shifts better? We don’t have a clear-cut answer to that," says Caruso. "One of the problems is that the studies often don’t give us enough details about the work schedules."

Overtime is a research area that is just gaining more attention, she notes. In a handful of studies, overtime was linked to "unhealthy weight gain," increased smoking and alcohol use, and poorer neuropsychological test performance.

Yet there are far fewer studies on the effects of overtime than on other work schedules, such as night shifts and rotating shifts, says Caruso. She is midway through a comprehensive study that will use overtime diaries and sleep/activity diaries to track the work life of nurses. The study will include information on demographics, home environment, child care, second jobs, elder care, educational courses, health history, medications, the family’s health history, and sleep characteristics, she says.

"Coping styles probably influence how people respond to these work schedules," she says.

Nursing shortages have led to increased pressure on nurses to work overtime. The American Nurses Association (ANA) has lobbied for state and federal legislation to restrict mandatory overtime for nurses.

A number of states have responded. For example, a new West Virginia law prohibits hospitals from mandating nurses to accept an assignment of overtime. In Connecticut, hospitals may not require a nurse to work more than a predetermined scheduled work shift except in certain circumstances, such as a public health emergency.

In Oregon, nurses may not be required to work more than two hours beyond a regularly scheduled shift or 16 hours in a 24-hour time period.

"We’ve always been concerned about overtime and its implications for patients. Our concern has broadened also to consider the implications for nurses and other health professionals in terms of health and safety," says Katherine Kany, RN, of the ANA’s Department of Nursing Practice and Policy.

Studies will shed light on how much a person can safely work, she says. "We have people working 12 hours [in a shift], anyway. You keep them overtime for even half a shift, and that’s 18 hours. I’ve actually talked to nurses who worked 20 hours in critical care areas.

"The reality is that people are working way too long," Kany adds. "There are implications for patients and implications for health care workers."


1. Caruso CC, Hitchcock EM, Dick RB, et al. Overtime and Extended Work Shifts: Recent Findings on Illnesses, Injuries, and Health Behaviors. Cincinnati: National Institute for Occupational Safety and Health (Publication No. 2004-143); 2004.

2. Lipscomb JA, Trinkoff AM, Geiger-Brown J, et al. Work-schedule characteristics and reported musculoskeletal disorders of registered nurses. Scand J Work Environ Health 2002; 6:394-401.