Time-Related Aspects of the Healthy Worker Survivor Effect

Details

• Personal Author:
  McKelvey W ; Richardson D ; Steenland, Kyle ; Wing S
• Description:
  PURPOSE: Health is important for continued employment and therefore continued accrual of occupational exposure; furthermore, steady employment can benefit health. Consequently, bias can occur in estimates of cumulative exposure-mortality associations. This has been called the healthy worker survivor effect (HWSE). The processes associated with the HWSE tend to lead to variation in mortality rates with time-since-termination of employment, most notably a peak in mortality shortly after termination of employment. We use simulations and an empirical example to demonstrate that time-since-termination can be a confounding factor in analyses of occupational-exposure-mortality associations. METHODS: Simulation data were generated for 20,000 workers followed for 40 years under a model of no effect of employment duration (a proxy for cumulative exposure) on mortality. Proportional hazards regression methods were used to quantify exposure-mortality associations and evaluate methods to control for the HWSE. Results were derived after 100 iterations of the simulation. Relationships between employment duration and mortality were also investigated in a cohort of 122,247 male utility workers with adjustments for time since termination. RESULTS: Simulation data show a peak in mortality rates in the first year after termination of employment which declined in magnitude with continued time since termination of employment; average employment duration also declined with time since termination of employment. This led to confounding of cumulative-exposure-mortality associations, with spurious evidence of a positive association between cumulative exposure and mortality in the post-termination period. Adjustment for time-since-termination eliminated this spurious association; in contrast, adjustment for a binary indicator of employment status led to positively-biased relative rate estimates. A similar pattern was observed in analyses of utility worker data. The log relative rate of all cancer mortality is -0.12+/-0.03 per decade of employment without adjustment for time-since-termination, and -0.01+/-0.03 with adjustment for time-since-termination of employment. CONCLUSIONS: The HWSE can lead to temporal variation in mortality rates that is correlated with cumulative exposure. Under these conditions, adjusting for time-since-termination of employment may reduce bias in estimates of cumulative-exposure-mortality trends more effectively than the commonly-used method of adjusting for a binary indicator of employment status. [Description provided by NIOSH]
• Subjects:
  Epidemiology Mortality Occupational Health Race Factors Safety Sex Characteristics Workplace
• Keywords:
  Humans Mortality-rates Mortality-surveys Racial-factors Sex-factors Statistical-analysis Workplace-monitoring
• ISSN:
  1047-2797
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  North Carolina ; Ohio ; OSHA Region 10 ; OSHA Region 4 ; OSHA Region 5 ; Washington
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  DSHEFS - Division of Surveillance, Hazard Evaluations, and Field Studies
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  14
• Issue:
  9
• NIOSHTIC Number:
  nn:20029372
• Citation:
  Ann Epidemiol 2004 Oct; 14(9):633-639
• Contact Point Address:
  Department of Epidemiology, School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
• Email:
  david_richardson@unc.edu
• CAS Registry Number:
  Plutonium (CAS RN 7440-07-5)
• Federal Fiscal Year:
  2005
• Performing Organization:
  Department of Epidemiology; School of Public Health; University of North Carolina
• Peer Reviewed:
  True
• Start Date:
  19960930
• Source Full Name:
  Annals of Epidemiology
• End Date:
  20010929
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:43d8041f1e7e90930a9a88fabcdc82b5927710f783ede6fee6f5dd118f6789ea3c98ec15e9e0de61d96603983bc585928a29e35c568a9f36186be4559d8e4643
• Download URL:
  https://stacks.cdc.gov/view/cdc/190363/cdc_190363_DS1.pdf
• File Type:
  [PDF - 137.49 KB ]