Shift Work: An Occupational Health and Safety Hazard. Sandra Buxton, BA (Hons) This thesis is presented for the degree of Master of Philosophy

Transcription

1 Shift Work: An Occupational Health and Safety Hazard Sandra Buxton, BA (Hons) This thesis is presented for the degree of Master of Philosophy of Murdoch University 2003

2 ii I declare that this thesis is my own account of my research and contains as its main content work which has not previously been submitted for a degree at any tertiary education institution. Sandra Buxton

3 iii ABSTRACT Shift work is a major feature of modern work practices. It involves individuals working at times considered unconventional for most workers, such as at night. Although the community often benefits from such work practices, shift work can be hazardous, for both the workers and the community. The thesis reviews the main problems of shift work, especially when involving night work. These are: an increased risk for accidents and errors; increased sleepiness and fatigue due to difficulties sleeping; increased health problems; and disruption to family and social life. Strategies to limit the risk associated with these hazards are also reviewed, and include using knowledge of circadian principles to plan shift schedules, sleeping schedules and meal times; planned napping; consideration of the work environment; and newer techniques such as using bright lights and melatonin. While this information is known to the research community, it has not filtered down to many shift work workplaces and thus has had little if any positive effect on actual shift work practices. For a change in shift work practices to occur, the research knowledge must become available to every shift work workplace, as must some incentive or motivation to ensure that workplaces make the necessary changes. The Occupational Health and Safety (OHS) laws provide such a framework. Considering shift work as an OHS hazard would ensure that all shift work workplaces identified the hazards of shift work, conducted a risk assessment to identify the risk associated with the hazards, and then implemented the appropriate strategies, from the hierarchy of shift work hazard control measures, for both employers and employees, to fulfil their duty of care to minimise the risks. Considering shift work as an OHS issue would ensure that the research information was used as intended to improve the safety, performance, and quality of life of all shift workers. The present thesis reviews the shift work research and introduces an OHS perspective as a method to manage shift work effectively.

4 iv TABLE OF CONTENTS 1. INTRODUCTION What is Shift Work? Shift Work Statistics Working at Night The body clock the circadian rhythm system... 4 Circadian Rhythm Desynchronisations Sleep loss the homeostatic need for sleep The Adverse Effects of Shift Work How to Help Shift Workers The Occupational Health and Safety Perspective Overall Aim of the Thesis Overview of the Thesis PART 1: THE HAZARDS ASSOCIATED WITH SHIFT WORK ACCIDENTS AND INJURY RISK Increased Sleepiness and Decreased Performance at Night Occupational Injury Data Studies finding no increase in accident risk on the night shift Studies finding an increase in accident risk on the night shift Accident risk and confounding factors Shift Workers and Driving Summary SLEEP The Sleep of Shift Workers Complaints with Sleeping and Sleepiness in Shift Work Summary HEALTH Sleep Disruption, Sleep Loss and Health Effects Gastrointestinal Problems... 60

5 v 4.3 Cardiovascular Disease Problems Blood pressure and hypertension ECG measures of heart function Shift Work, Depression, and the Antidepressive Effects of Sleep Loss Shift Work and Women How are Shift Work and Ill-Health Linked? Control / Autonomy Stress a stimulus-based model Stress a transactional ( stress-strain ) model Social support Summary Shift Work and Health Research - Study Limitations Methodological differences The healthy worker effect Absenteeism data Job dimensions Lack of longitudinal studies Summary FAMILY AND SOCIAL LIFE Family and Social Adjustment as a Function of the Type of Shift Leisure Time for Shift Workers Partners Children Partners and Children Summary PART 2: FACTORS THAT CAN AFFECT SHIFT WORK TOLERANCE SHIFT WORK SCHEDULING FACTORS Shift Timing Night, Morning, and Afternoon Shifts Night shift Morning and afternoon shift

6 vi 6.2 Speed of Rotation Rapidly Rotating vs. Slow or Permanent Night Rosters? Studies favouring rapidly rotating rosters Studies favouring slow, or permanent night shift rosters Summary Direction of Rotation Backward or Forward Rotating Rosters? Shift Length - Extended Work Hours versus 12 hour shifts Overtime and long weekly working hours Summary Time Between Shifts Rest Breaks During Work Regularity of Start Times - Shift Work and Jet Lag Twelve-Hour Time Zone Changes and the Bimodal Circadian Rhythm System Summary INDIVIDUAL DIFFERENCES Age Gender Age and Gender Physical Fitness Circadian Type Psychological Measures Complex Interactions Between Psychophysiological Variables Can Shift Work Tolerance be Predicted from Psychological Variables? Circadian Rhythm Markers of Tolerant/Non-Tolerant Shift Workers Stable differences in the circadian rhythm system Differences in adaptability of the circadian rhythm system Summary NAPPING FOR SHIFT WORKERS Sleep Loss Naps during a night shift

7 vii Naps before a night shift the maintenance nap Summary Nap Duration Sleep Period length Core Sleep Anchor Sleep Nap length How long do nap benefits last? Naps and the next main sleep period Summary The Circadian Rhythm in Ability to Sleep When to Take a Nap Ability to sleep The outcomes of differently timed naps Summary Sleep Inertia and Groggy Performance Effects After a Nap: The Time Between the Nap and the Next Performance Period Slow-wave sleep within naps Sleep loss prior to napping Circadian rhythm timing of nap taking Summary Using Napping in the Real World as a countermeasure to Shift Work Fatigue Summary BRIGHT LIGHT, MELATONIN, STIMULANTS, AND SEDATIVE- HYPNOTICS FOR SHIFT WORKERS Bright Light and Melatonin Bright light Melatonin Bright light and melatonin together Stimulants Caffeine Modafinil Sedative Hypnotics

8 viii 9.4 Summary PART 3: THE OHS APPROACH TO MANAGING SHIFT WORK THE SHIFT WORK HAZARD CONTROL STRATEGIES The Occupational Health and Safety Approach The Occupational Health and Safety Hierarchy of Intrinsic Shift Work Hazard Control Measures Main sleep timing Fast Shift Rotations Slow Shift Rotations Permanent Night Shift Napping Sleep environment the sleep hygiene rules Meal timing and content Foods to Avoid on the Night Shift Foods to Eat on the Night Shift Domestic and social strategies Health status - risk factors and contraindications for shift work Risk Factors Contraindications Fitness and exercise The Occupational Health and Safety Hierarchy of Extrinsic Shift Work Hazard Control Measures Shift work scheduling recommendations Recommendations for Good Shift Work Schedules Additional Things Employers can do to Help Shift Workers Shift Work Scheduling for the Older Shift Worker Work conditions to improve performance on night shift Health interventions and monitoring Bright light, melatonin, caffeine, and sedative-hypnotic strategies Bright Light Melatonin Caffeine and Napping

9 ix Sedative-hypnotics Summary THE ROLE OF EDUCATION IN MANAGING SHIFT WORK Designing Shift Work Education Evaluating Shift Work Education Summary SUMMARY AND CONCLUSIONS REFERENCES

10 x ACKNOWLEDGEMENTS The communications of the following people are gratefully acknowledged Assoc. Prof. Laurence Hartley Institute for Research in Safety and Transport Psychology, Murdoch University Western Australia. Gerald P Krueger, PhD, CPE Krueger Ergonomics Consultants Alexandria, Virginia USA. Prof. Torbjorn Åkerstedt Psykosocial Medicin & Stressforskning/Folkhälsovetenskap Inst for Psychosocial Medicine & Section for Stress Research Department of Public Health Sciences Karolinska Institutet, Stockholm. Prof. Dr. Frida Marina Fischer Department of Environmental Health School of Public Health University of São Paulo, Brazil.

11 xi Dr. David F. Dinges Professor of Psychology in Psychiatry Chief, Division of Sleep and Chronobiology Director, Unit for Experimental Psychiatry Department of Psychiatry, University of Pennsylvania School of Medicine. Dr. Naomi L. Rogers Division of Sleep and Chronobiology Unit for Experimental Psychiatry Department of Psychiatry, University of Pennsylvania School of Medicine. Assoc. Prof. Philippa Gander Sleep-Wake Research Centre University of Otago Wellington School of Medicine New Zealand. Serge Casoti WA Freight Lines, Perth, Western Australia. Lance Poore W.A. Department of Transport, Perth, Western Australia.