Abstract
Employees within an occupational cohort may demonstrate a moire favorable mortality experience while maintaining employment than those who leave employment. At the stone time, they may experience an apparent decline in health with time-since-hire. The time-since-hire effect may occur independently of exposure but may nevertheless result in groups categorized by cumulative exposure that are not comparable. Controlling for time-since- hire appears to solve this problem. To quantify, the empirical bias in estimates of exposure effect due to confounding from time-since-hire, we analyzed two occupational cohorts using Poisson regression with and without adjustment for time-since-hire or time-since-start-of-follow-up. In a cohort exposed to airborne arsenic, a strong dose-response relation with respiratory cancer mortality had been established. In a cohort exposed to external, penetrating ionizing radiation, a weak and controversial dose-response relation had been reported. The parameter estimates relating exposure to disease from the models that explicitly adjusted for time-since-hire or time- since-start-of-follow-up are within 10% of the estimates from models that did not. It appears, from this empirical analysis of two datasets, that occupational studies may not need to adjust explicitly for such time-related factors as time-since-hire or time-since-start-of-follow-up if these are implicitly controlled through other variables in the model.
Original language | English (US) |
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Pages (from-to) | 415-418 |
Number of pages | 4 |
Journal | Epidemiology |
Volume | 6 |
Issue number | 4 |
State | Published - 1995 |
Externally published | Yes |
Keywords
- bias
- cohort studies
- epidemiologic methods
- models
- occupational exposures
- time- related factors
ASJC Scopus subject areas
- Epidemiology