The time-trend and the relation between smoking and circulating selenium concentrations in Norway

The objectives of this study were to investigate biomarkers of selenium status in relation to smoking habits and to analyze the time-trend of selenium in serum (S-Se) in Norway during the time period 1995–2006. The impact of smoking habits was investigated in a population recruited to a cross-sectional study of blue-collar workers in the southern part of the country ( n=98). The time-trend was studied in all subjects who delivered blood samples for the determination of S-Se to a large commercial clinical chemistry laboratory in Norway. Smokers had 0.14 and 0.20 μmol/L lower concentrations of selenium in whole blood (B-Se) and serum, respectively, than non-smokers. The amount of smoking, as assessed by the serum cotinine concentration, was negatively associated with the B-Se concentration (Pearson's r=−0.43). The 1/3 of the blue-collar workers with the lowest concentrations of B-Se or S-Se had lower activity of glutathione peroxidase in serum (S-GSHpx) than the remaining subjects. Snuff users had about the same levels of B-Se and S-Se as the non-smokers, although they had about the same amount of nicotine metabolites in urine and serum as the smokers. A decreasing trend of S-Se was observed during the observation period from 1995 to 2006. The mean concentration was 1.26 μmol/L in 1995, while the lowest mean concentration was measured in 2003 (1.01 μmol/L). Smoking, but not snuffing, is associated with lower concentrations of B-Se and S-Se. The reduction of B-Se is negatively associated with the nicotine biomarker cotinine in serum. A substantial proportion of blue-collar workers had not maximized the activity of S-GSHpx. Selenium status may have become poorer since 1995.