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A structural approach to address the healthy-worker survivor effect in occupational cohorts: an application in the trucking industry cohort
  1. Andreas M Neophytou1,2,
  2. Sally Picciotto2,
  3. Jaime E Hart1,3,
  4. Eric Garshick1,4,
  5. Ellen A Eisen2,
  6. Francine Laden1,3
  1. 1Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA
  2. 2Division of Environmental Health Sciences, University of California, School of Public Health, Berkeley, California, USA
  3. 3Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
  4. 4Primary and Critical Care Medicine Section, VA Boston Healthcare System, Boston, Massachusetts, USA
  1. Correspondence to
    Dr Andreas M Neophytou, Division of Environmental Health Sciences, UC Berkeley School of Public Health, 772 University Hall, Berkeley, CA 94720, USA; aneophytou{at}berkeley.edu

Abstract

Background Occupational cohort studies are often challenged by the Healthy Worker Survivor Effect, which may bias standard methods of analysis. G-estimation of structural failure time models is an approach for reducing this type of bias. Accelerated failure time models have recently been applied in an occupational cohort but cumulative failure time models have not.

Methods We used g-estimation of a cumulative failure time model to assess the effect of working as a long-haul driver on ischaemic heart disease mortality in a cohort of 30 448 men employed in the unionised US trucking industry in 1985. Exposure was defined by job title and based on work records. We also applied g-estimation of an accelerated failure time model as a sensitivity analysis and approximated HRs from both models to compare them.

Results The risk ratio (RR) obtained from the cumulative failure time model, comparing the observed risk under no intervention to the risk had nobody ever been exposed as a long-haul driver, was 1.09 (95% CI 1.02 to 1.16). The RR comparing the risk had everyone been exposed as long-haul driver for 8 years to the risk had nobody ever been exposed was 1.20 (95% CI 1.04 to 1.46). After HR approximations, accelerated failure time model results were similar.

Conclusions The cumulative failure time model can effectively control time-varying confounding by Healthy Worker Survivor Effect, and provides an easily interpretable effect estimate. RRs estimated from the cumulative failure time model indicate an elevated ischaemic heart disease mortality risk for long-haul drivers in the US trucking industry.

  • Methodology, speciality

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