Overtime and Extended Work Shifts: Recent Findings on Illnesses, Injuries, and Health Behaviors Claire C. Caruso, Ph.D., R.N. Edward M. Hitchcock, Ph.D. Robert B. Dick, Ph.D. John M. Russo, Ph.D. Jennifer M. Schmit, M.A. U. S. Department of Health and Human Services Centers for Disease Control and Prevention National Institute for Occupational Safety and Health April 2004 Overtime and Extended Work Shifts Ordering Information To receive documents or other information about occupational safety and health topics, contact the National Institute for Occupational Safety and Health (NIOSH) at NIOSH Publications Dissemination 4676 Columbia Parkway Cincinnati, OH 45226-1998 Telephone: 1-800-35-NIOSH (1-800-356-4674) Fax: 1-513-533-8573 E-mail: [email protected] or visit the NIOSH Web site at www.cdc.gov/niosh This document is in the public domain and may be freely copied or reprinted. Disclaimer: Mention of any company, product, policy, or the inclusion of any reference does not constitute endorsement by NIOSH. DHHS (NIOSH) Publication No. 2004-143 ii Recent Findings on Illnesses, Injuries, and Health Behaviors Foreword The average number of hours worked annually by workers in the United States has increased steadily over the past several decades and currently surpasses that of Japan and most of Western Europe. The influence of overtime and extended work shifts on worker health and safety, as well as on worker errors, is gaining increased attention from the scientific community, labor representatives, and industry. U.S. hours of serv- ice limits have been regulated for the transportation sector for many years. In recent years, a number of states have been considering legislation to limit mandatory overtime for health care workers. The volume of legislative activity seen nationwide indicates a heightened level of societal concern and the timeliness of the issue. This document summarizes recent scientific findings concerning the relationship between overtime and extended work shifts on worker health and safety. The number of studies increased dramatically over the past few years, but important research questions remain. I am confident that this document will contribute to an informed discussion of these issues and provide a basis for further research and analysis. John Howard, M.D. Director, National Institute for Occupational Safety and Health iii Overtime and Extended Work Shifts Executive Summary PURPOSE vigilance on task measures, and increased injuries. Two studies examining physicians who This report provides an integrative review of 52 worked very long shifts reported deterioration on recently published research reports that examine various measures of cognitive performance. the associations between long working hours and illnesses, injuries, health behaviors, and perform- When 12-hour shifts combined with other work- ance. The report is restricted to a description of related demands, a pattern of more adverse find- the findings and methods and is not intended as ings was detected across studies. Six studies an exhaustive discussion of all important issues examining 12-hour shifts combined with more related to long working hours. Findings and than 40 hours of work per week reported increas- methods are summarized as reported by the origi- es in health complaints, deterioration in perform- nal authors, and the study methods are not criti- ance, or slower pace of work. Two studies com- cally evaluated for quality. paring 8- and 12-hour schedules during day and night shifts reported that 12-hour night shifts SUMMARY were associated with more physical fatigue, smoking, or alcohol use. Two studies examining In 16 of 22 studies addressing general health start times for 12-hour shifts reported that decre- effects, overtime was associated with poorer per- ments in alertness or more health complaints ceived general health, increased injury rates, were associated with early 6:00 a.m. start times. more illnesses, or increased mortality. One meta- One study examining 12-hour shifts in hot work analysis of long work hours suggested a possible environments reported a slower pace of work as weak relationship with preterm birth. Overtime compared with shorter shifts. Another study was associated with unhealthy weight gain in two examining high workloads during 12-hour shifts studies, increased alcohol use in two of three showed increased discomfort and deterioration in studies, increased smoking in one of two studies, performance as compared with shorter shifts. and poorer neuropsychological test performance in one study. Some reports did not support this More definitive statements about differences trend, finding no relationship between long work between 8-hour and 12-hour shifts are difficult hours and leisure-time physical activity (two of because of the inconsistencies in the types of three studies) and no relationship with drug abuse work schedules examined across studies. Work (one study). schedules differed by the time of day (i.e., day, evening, night), fixed versus rotating schedules, A pattern of deteriorating performance on psy- speed of rotation, direction of rotation, number of chophysiological tests as well as injuries while hours worked per week, number of consecutive working long hours was observed across study days worked, number of rest days, and number findings, particularly with very long shifts and of weekends off. All of these factors could have when 12-hour shifts combined with more than 40 interacted with overtime and influenced study hours of work a week. Four studies that focused results. Also, some studies did not report how on effects during extended shifts reported that the many hours participants worked per week or 9th to 12th hours of work were associated with other details about the work shifts, which compli- feelings of decreased alertness and increased cated the assessment of their results. The many fatigue, lower cognitive function, declines in iv Recent Findings on Illnesses, Injuries, and Health Behaviors differences in the 8- and 12-hour shift schedules studied may have accounted for their contradicto- ry findings. Few studies have examined related topics, such as the combined influence of shift work and overtime, or how worker control over their work time and mandatory overtime might influence their health. Some studies examined functional abilities or injuries during the 1st to 12th hours of work, but little has been reported about effects after the 12th hour. Few studies have investigated the influence of long working hours on the health and safety of women or older workers. Few stud- ies have explored how long working hours influ- ence workers with pre-existing health problems, or how the hours relate to symptom management and the course of common chronic diseases. Little data are available regarding the influence of occupational exposures (i.e., chemical, heat, noise, lifting) in combination with long working hours on health and safety. Although the number of published studies exam- ining long working hours appears to be increas- ing, many research questions remain on how overtime and extended work shifts influence worker health and safety. v Overtime and Extended Work Shifts Table of Contents Foreword. iii Executive Summary . iv Tables . viii Abbreviations . ix Acknowledgments. x 1. Introduction. 1 2. Description of the Work Schedules and the Samples. 3 3. Health and Safety Findings . 5 3.1 Findings Associated with Overtime. 5 3.1a Overtime and Cardiovascular Findings. 5 3.1b Overtime and Other Illnesses. 8 3.1c Overtime and Injuries . 12 3.1d Overtime and Health Behaviors . 12 3.1e Overtime and Performance. 12 3.2 Findings Associated with Extended Work Shifts . 12 3.2a Extended Work Shifts and Illnesses. 17 3.2b Extended Work Shifts and Injuries. 17 3.2c Extended Work Shifts and Health Behaviors. .17 3.2d Extended Work Shifts and Performance . 17 3.3 Findings Associated with Extended Work Shifts Combined with More than 40-Hours Work per Week . 21 3.3a Extended Work Shifts Combined with More than 40-Hours Work per Week and Illnesses . 21 3.3b Extended Work Shifts Combined with More than 40-Hours Work per Week and Injuries . 24 3.3c Extended Work Shifts Combined with More than 40-Hours Work per Week and Health Behaviors . 24 3.3d Extended Work Shifts Combined with More than 40-Hours Work per Week and Performance . 24 3.4 Findings Associated with Very Long Shifts . 24 vi Recent Findings on Illnesses, Injuries, and Health Behaviors 3.4a Very Long Shifts and Other Illnesses. 24 3.4b Very Long Shifts and Performance . 24 4. Summary . 27 4.1 Overtime . 27 4.2 Extended Work Shifts . 27 4.3 Other Work Schedule Characteristics. 28 4.4 Compensation, Vacation Time, Commute Time . 28 4.5 Gender and Age . 28 4.6 Chronic Health Problems. 28 4.7 Occupational Exposures. 29 5. Concluding Remarks . 30 References . 31 vii Overtime and Extended Work Shifts Tables Table 1. Countries Where Studies Were Conducted . 4 Table 2. Types of Work Investigated . 4 Table 3. Studies Examining Overtime and Cardiovascular Outcomes: Methods and Findings . 6 Table 4. Studies Examining Overtime and Other Illnesses: Methods and Findings . 9 Table 5. Studies Examining Overtime and Injuries: Methods and Findings . 13 Table 6. Studies Examining Overtime, Health Behaviors, and Performance Outcomes: Methods and Findings . 14 Table 7. Studies Examining Extended Work Shifts: Methods and Findings . 18 Table 8. Studies Examining Extended Work Shifts Combined with More than 40 Hours per week: Methods and Findings . .22 Table 9. Studies Examining Very Long Work Shifts: Methods and Findings . ..