Objectives To examine further the association between endotoxin and risk of lung cancer among Shanghai women textile workers in an extended follow-up of the cohort. The initial follow-up indicated an inverse exposure-response relation.
Method We updated a case-cohort study nested within a cohort of 267 400 women. We compared exposure histories of 1456 incident lung cancers cases diagnosed during 1989–2006 with those of a reference subcohort of 3022 workers who were free of lung cancer at the end of follow-up. Endotoxin exposures were based on a quantitative job/exposure matrix. Relative risks (hazard ratios [HR]) associated with cumulative exposure, adjusted for age and smoking history, were estimated by Cox proportional hazards modelling adapted for the case-cohort design. We conducted exposure-response trend analyses for cumulative exposures lagged by 0, 10, and 20 years, and separately for time windows of <15 and >15 years since first exposure.
Results Overall, we observed no associations between cumulative exposure and lung cancer. In contrast, analyses by exposure time windows revealed a modestly elevated risk at the highest 3 exposure quintiles for exposures that occurred >15 years since first exposure; HR=1.28 (95% CI 0.90–1.82), HR=1.27 (95% CI 0.93–1.73), and HR=1.27 (95% CI 0.91–1.77), respectively; p-trend = 0.13.
Conclusions Exposures to endotoxin with long-term, relatively intense exposures were at most weakly associated with lung cancer risk in this cohort. The findings do not support a protective effect of endotoxin, but are suggestive of possible lung cancer promotion with increasing time since first exposure.
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