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Healthy worker effect in cohort studies on chronic bronchitis.
Katja Radon1, Mark Goldberg, Margaret Becklake
1Department of Medicine, Joint Departments of Epidemiology and Biostatistics and Occupational Health, McGill University, Montreal, Quebec, Canada. Katja.Radon@arbeits.med.uni-muenchen.de
Scandinavian Journal of Work, Environment & Health
|November 16, 2002
Summary
The healthy worker survivor effect may underestimate respiratory symptoms in occupational studies. Workers leaving cohorts had a higher prevalence of chronic bronchitis, indicating a significant bias.
Area of Science:
- Occupational Health
- Epidemiology
- Respiratory Medicine
Background:
- The healthy worker effect (HWE) is recognized in mortality studies, but its impact on respiratory symptom research is less understood.
- Two HWE mechanisms exist: health-based employment selection (healthy hire) and health-based attrition (healthy worker survivor effect).
Purpose of the Study:
- To quantify the healthy worker survivor effect in occupational cohort studies investigating chronic bronchitis symptoms.
Main Methods:
- A meta-analysis was conducted on occupational cohort studies.
- Studies were identified through Medline searches (1980-2001) and reference list reviews.
- Eight cohort studies met the inclusion criteria.
Main Results:
- The pooled odds ratio for chronic bronchitis prevalence among workers leaving cohorts was 1.23 (95% CI: 1.04-1.44).
- This indicates a 23% higher prevalence of chronic bronchitis in those who discontinued study participation.
Conclusions:
- Failure to account for the healthy worker survivor effect can lead to underestimation of respiratory symptoms in exposed worker populations.
- This bias is crucial to consider in occupational cohort studies of respiratory health.