title: The time-trend and the relation between smoking and circulating selenium concentrations in Norway.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  Smokers had 0.14 and 0.20 micromol/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 micromol/L in 1995, while the lowest mean concentration was measured in 2003 (1.01 micromol/L).
  
  
  CONCLUSIONS
  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.
authors.affiliation: National Institute of Occupational Health, Oslo, Norway. dag.ellingsen@stami.no
authors.forename: Dag G
authors.initials: DG
authors.lastname: Ellingsen
authors.forename: Yngvar
authors.initials: Y
authors.lastname: Thomassen
authors.forename: Pål
authors.initials: P
authors.lastname: Rustad
authors.forename: Pål
authors.initials: P
authors.lastname: Molander
authors.forename: Jan
authors.initials: J
authors.lastname: Aaseth
mesh_terms: D000328:Adult; D000368:Aged; D003367:Cotinine / Q000097:blood / Q000652:urine; D003430:Cross-Sectional Studies; D005260:Female; D005979:Glutathione Peroxidase / Q000097:blood; D006801:Humans; D008019:Life Style; D008297:Male; D008875:Middle Aged; D009538:Nicotine / Q000097:blood / Q000652:urine; D009664:Norway; D012643:Selenium / Q000097:blood*; D012907:Smoking / Q000097:blood*; D014131:Trace Elements / Q000097:blood*
chemical_list: D014131:Trace Elements; D009538:Nicotine; D005979:Glutathione Peroxidase; D012643:Selenium; D003367:Cotinine