Research substantiates the adverse effect of overtime on productivity and morale. A report published by the Center for Diseases Control and Prevention and National Institute of Occupational Safety and Health, under the U. S. Department of Health and Human Services revealed that 16 out of the 22 major studies surveyed associated overtime with poorer general health, increased injury rates, more illnesses, and increased mortality. Following are examples of some of these studies (links can be found in the reference section.)
A 1996 study by Proctor et al. report that working overtime results in loss of cognitive function and erosion in ability to prioritize and plan tasks. Extended work hours also Increase incidences of on the job accidents.
A 1998 study by Rosa et al. reports a direct relationship between longer shifts and fatigue, especially when the extended hours occur during night shifts. The study found highest fatigue levels in 12-hour night shifts.
A 2000 study by Macdonald and Bendak associates a longer workday with deterioration in grammatical reasoning and alertness.
A 2001 research by Van der Hulst and Geurts places an employee performing overtime with increased risk for somatic complaints, burnout, and work-life imbalance, all ultimately leading to loss of morale.
A 2004 Unscheduled Absence Survey by CCH Incorporated revealed a direct association with high overtimes and high absenteeism. Unscheduled absenteeism costs U.S. employers $3,600 per hour owing to loss of productivity and work held up.
Another 1998 study by Smith et al. reports that 12-hour shifts with employers having some flexibility in start times led to better psychological wellbeing and alertness levels among employees, suggesting the ill-effects of overtime may be owing to rigid schedules. Flextime may mitigate some of the ill effects of overtime.
An article by Michelle Rafter, The Yawning of a New Era, published December 2010 in Workforce Management Magazine, documents facts related to the rise of human fatigue in the workplace and illustrates the case of nurses’ work hours at Allegheny General Hospital in Pittsburgh Pennsylvania. The hospital, to cut costs had mandated compulsory overtime for nurses, but it only resulted in increased fatigue levels, and consequently more sick leaves. These sick leaves further increased demand for overtime, causing the formation of a vicious cycle. The loss of productivity and frequent absenteeism led to performance related issues, again causing loss of morale. The hospital finally ended the policy of compulsory overtime and the vicious cycle of low productivity and sick leaves owing to fatigue ended.
Although some studies do not find any association between overtime and productivity, or state that a direct association remains difficult to establish owing to the intervention of many other complex factors, the negative association remains fairly well-established.