Cardio-Metabolic Risk of Shift Work: Sleep Loss vs. Circadian Disruption

Details

• Personal Author:
  Hanlon EC ; Knutson KL ; Leproult R ; Pannain S ; Van Cauter E
• Description:
  This project addresses the occupational health issues that affect shift workers as compared to regular day workers. Worldwide in industrialized countries, nearly 20% of working adults are shift workers. Prospective epidemiologic studies have indicated that shift work is associated with an increased risk of type 2 diabetes and cardiovascular disease but the underlying mechanisms remain unclear. Shift work is generally associated with chronic sleep loss and poor sleep quality, which both have an adverse effect on glucose tolerance and cardiovascular function. Most shift workers are active during the biological night resulting in circadian misalignment, a condition where the behavioral sleep-wake schedule is not aligned with the endogenous circadian rhythm generated by the master circadian clock in the brain. While insufficient sleep has been identified as a risk factor for obesity, diabetes and hypertension, the clinical significance of circadian misalignment is still poorly understood. In a previous 2-week laboratory study, our group showed that circadian misalignment impairs insulin sensitivity, increases inflammation and adversely affects cardiovascular function, independently of sleep loss. The present project represents a translation from short-term sleep and circadian disturbances in the laboratory to the chronic exposure of shift workers in real life. The overall goal is to determine whether shift workers have a higher cardio-metabolic risk than day workers, and whether the accumulated sleep debt and the degree of circadian misalignment predict the severity of cardio-metabolic alterations. Further, we examined whether sleep extension with fixed nocturnal bedtimes is able to improve cardio-metabolic risk. Our approach was to enrolled full-time day workers and shift workers who were matched for age, sex, race, body mass index and all worked in a similar environment. Following extended ambulatory recording of the sleep-wake cycle, the participants underwent a laboratory assessment of sleep, circadian rhythms and cardio-metabolic risk. A subset of subjects participated in a 1-week "proof of concept" study designed to extend and align sleep times. The participants continued their usual daily activities but slept in the laboratory every night with fixed bedtimes in total darkness of 10h per night. Day workers and shift workers had similar habitual sleep duration (<6h per night) but night-to-night variability was greater in shift workers. Despite similar demographics and degree of sleep restriction, the shift workers had higher blood glucose, a lower insulin response to oral glucose and were more likely to be glucose intolerant. Statistical analysis indicated that higher glucose levels were related to sleep irregularity rather than duration. Remarkably, both day and shift workers were able to increase actual sleep duration by more than 2h during the entire week of bedtime extension. A key finding is that they experienced a significant reduction in their risk of diabetes, objectively assessed using an intravenous tolerance test. The correction of metabolic deficits tended to be more robust in day workers than shift workers, despite similar amounts of sleep extension. The findings identify sleep irregularity as a robust predictor of cardio-metabolic risk in shift work and have implications for the design of work schedules that minimize adverse health consequences. [Description provided by NIOSH]
• Subjects:
  Cardiovascular Diseases Cardiovascular System Circadian Rhythm Demography Energy Metabolism Occupational Exposure Occupational Health Safety Sleep Sleep Initiation And Maintenance Disorders
• Keywords:
  Cardiovascular Disease Chronic Exposure Circadian Rhythms Demographic Characteristics Hormone Activity Humans Metabolic Effects Obesity Risk Assessment Shift Workers Sleep Deprivation Sleep Disorders Work Schedules

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• Series:
  Grant Final Reports
• Publisher:
  National Institute for Occupational Safety and Health
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Final Grant Report
• Place as Subject:
  Illinois ; OSHA Region 5
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  OEP - Office of Extramural Programs
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  1-27
• NIOSHTIC Number:
  nn:20052688
• Citation:
  Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, R01-OH-009482, 2017 Apr; :1-27
• Contact Point Address:
  Eve Van Cauter, Ph.D., Frederick H. Rawson Professor, Section of Endocrinology, Diabetes and Metabolism, Department of Medicine, MC 1027, The University of Chicago, 5841 S. Maryland Avenue, Chicago, Illinois 60637-5418
• Email:
  evcauter@medicine.bsd.uchicago.edu
• Federal Fiscal Year:
  2017
• NORA Priority Area:
  Healthcare and Social Assistance
• Performing Organization:
  University of Chicago
• Peer Reviewed:
  False
• Start Date:
  20090901
• Source Full Name:
  National Institute for Occupational Safety and Health
• End Date:
  20150831
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:f21d0a038d3d31e7d577c7076faee8515f03d12696da0912c19c3b887647993ab4c69c5e022c624eda1e3c7be23e035e680b367382b11a0a7fbc9a7cdbfb1e50
• Download URL:
  https://stacks.cdc.gov/view/cdc/218720/cdc_218720_DS1.pdf
• File Type:
  [PDF - 1.31 MB ]