ORIGINAL ARTICLE Bias From Using Occupational Smoking Prevalence to Adjust Occupational Incidence Cohort Lung Cancer Mortality Rates

Objective: To describe how smoking correction factors based on comparing worker smoking prevalence with population smoking prevalence are biased if applied to an occupational incidence cohort. Methods: Relative rates of smoking for shorter-tenure workers derived from occupational cohort lung cancer studies were applied to incidence and prevalence population tenure distributions to calculate relative smoking estimates. Results: High smok-ing rates in short-tenure workers have little effect on prevalent worker rates (relative smoking estimates, 1.04 and 1.02) and much larger effect in occu-pational incidence populations (relative smoking estimates, 1.58 and 1.21), which have a much higher proportion of short tenure-workers. Conclusions: Smoking correction estimates derived from surveys of smoking habits in prevalent workers may introduce bias when applied to incidence workers because of very different proportions of short-tenure workers (length-time biased sampling). E fforts were made to indirectly assess the influence of tobaccosmoking in two lung cancer mortality studies1,2 of berylliu