Nested case-control study of occupational physical activity and prostate cancer among workers using a job exposure matrix

Objective We conducted a nested case-control study of 362 cases diagnosed between 1 January 1988 and 31 December 1999, and 1,805 matched controls to examine the association between occupational physical activity and prostate-cancer incidence among workers at a nuclear and rocket engine-testing facility in Southern California. Methods We obtained cancer incidence data from the California Cancer Registry and seven other state cancer registries. Data from company records were used to construct a job exposure matrix (JEM) for occupational physical activity during employment. Conditional logistic regression was used to estimate associations. Results With adjustment for occupational confounders, including socioeconomic status and trichloroethylene (TCE) exposure, high activity levels at work were inversely associated with prostate-cancer incidence among aerospace workers (odds ratio [OR] = 0.55; 95% CI = 0.32-0.95), but not among radiation workers (OR = 0.95; 95% CI = 0.43-2.1). Conclusions Our results suggest that adult men who are more continually active at work may have a decreased risk of prostate cancer.