Serum selenium and subsequent risk of prostate cancer

It is suspected that selenium is protective against prostate cancer, To tes t this hypothesis, we conducted a nested case-control study in a cohort of 9345 Japanese-American men examined between 1971 and 1977, At the time of e xamination, a blood specimen was obtained, and the serum was frozen, After a surveillance period of more than 20 years, 249 tissue-confirmed incident cases of prostate cancer were identified. Their stored sera and those of 24 9 matched controls were measured for selenium levels. Odds ratios for prost ate cancer, based on quartiles of serum selenium levels, were determined us ing the General Estimating Equations approach, The multivariate odds ratio for the highest quartile was 0.5 (95% confidence interval, 0.3-0.9) with a two-sided P for trend of 0.02, The inverse association was more notable for cases with advanced disease and for cases diagnosed 5-15 years after phleb otomy, However, the association was mainly present in current or past cigar ette smokers rather than nonsmokers, which leads to caution in the interpre tation of the results.