Toenail selenium concentration and lung cancer in male smokers (Finland).

Background: The objective of this investigation was to evaluate the association between toenail selenium concentration and lung cancer risk in male smokers. Methods: We conducted a nested case–control study within the Alpha–Tocopherol Beta–Carotene Cancer Prevention Study cohort. This substudy included 250 randomly selected incident lung cancer cases and 250 controls matched on age (up to ± 5 years), intervention group assignment, and date or randomization (±15 days). Odds ratios (ORs) and 95% confidence intervals (CIs) were determined using conditional logistic regression methods. Finland began fortification of argricultural fertilizers in the fall of 1984, increasing the dietary intake, plasma, and toenail selenium concentrations for the population. The present analyses were based on the calculated residual of toenail selenium after regressing it on date of randomization. The selenium residual and the interaction of the residual with date of randomization were included in models with smoking status and body mass index as covariates. Results: We observed a suggestion of a protective association for higher selenium status among men who entered the trial early (when the range of selenium values included very low levels). The OR for men with adjusted toenail selenium concentrations at the 75th percentile compared to those with the lowest selenium concentrations ranged between 0.20 (0.09–0.44) for men randomized earliest in the trail and 0.61 (0.27–1.41) for men randomized in the fifth year. Conclusions: These results suggest that low selenium status may be associated with increased risk for lung cancer.