title: Smoking reduction and biomarkers in two longitudinal studies.
abstract: OBJECTIVE
  To measure reduction in exposure to smoke in two population-based studies of self-reported smoking reduction not using nicotine replacement.
  
  
  METHODS
  Cross-sectional analyses of biomarkers and smoking.
  
  
  METHODS
  Data from two time-points in the Copenhagen City Heart Study (CCHS), 1981/83 and 1991/94, and the Copenhagen Male Study (CMS) in 1976 and 1985/86, respectively.
  
  
  METHODS
  There were 3026 adults who were smokers at both time-points in the CCHS and 1319 men smoking at both time-points in the CMS.
  
  
  METHODS
  Smoking status and tobacco consumption were assessed by self-completion questionnaire. Measurements of biomarkers of smoke intake were taken at the second time-point in the two studies: expired-air carbon monoxide (CO) in the CCHS and serum cotinine in the CMS. Biomarker levels in medium (15-29 g tobacco/day) and heavy (> 30 g/day) smokers at the first time-point who later reported a reduction in cigarettes per day of 50% or more without quitting were compared with continuing medium, heavy and light smokers (1-14 g/day) using linear regression. Sex (CCHS only), age, self-reported inhalation of smoke, duration of smoking, type of tobacco and amount smoked were included as covariates in multivariate models.
  
  
  RESULTS
  Heavy smokers who reduced did not show lower levels of biomarkers at follow-up. Medium smokers who reduced showed a reduction in cotinine but not CO. The reduction in cotinine was not commensurate with the reported reduction in consumption.
  
  
  CONCLUSIONS
  Long-term reductions in self-reported tobacco smoking are probably associated with, at best, modest reductions in smoke exposure.
authors.affiliation: The Copenhagen Centre for Prospective Population Studies, Institute of Preventive Medicine, Copenhagen University Hospital, Denmark. duegodt@dadlnet.dk
authors.forename: Nina S
authors.initials: NS
authors.lastname: Godtfredsen
authors.forename: Eva
authors.initials: E
authors.lastname: Prescott
authors.forename: Jørgen
authors.initials: J
authors.lastname: Vestbo
authors.forename: Merete
authors.initials: M
authors.lastname: Osler
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D003367:Cotinine / Q000097:blood; D003430:Cross-Sectional Studies; D005260:Female; D040261:Harm Reduction / Q000187:drug effects*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D000074606:Smoking Prevention; D014028:Tobacco Smoke Pollution / Q000517:prevention & control
chemical_list: D015415:Biomarkers; D014028:Tobacco Smoke Pollution; D003367:Cotinine