title: Late-onset smokers: how many, and associations with health behaviours and socioeconomic status.
abstract: OBJECTIVE
  Adolescence is considered a critical phase for smoking initiation, while smoking initiation in adulthood has received less attention. In the present study, we investigated smoking initiation in early adulthood, with an additional focus on how socioeconomic status (SES) relates to late-onset smoking.
  
  
  METHODS
  The Norwegian Longitudinal Health Behaviour Study followed a representative sample of adolescents (n=530) from age 13 (7th grade) to age 30 (years 1990-2007) through 9 waves of data collection. Information was collected on the adolescents' gender, smoking, alcohol use, cannabis use, physical activity, and SES. Those reporting to be smokers at age 30, but not at age 18, were defined as "late-onset smokers".
  
  
  RESULTS
  At age 30, 21% were daily smokers, of which 45% met our definition of late-onset smoking. Participants with a low SES had a higher odds ratio for late-onset smoking (OR=3.42) and a lower odds ratio for quitting smoking (OR=0.40) after adjusting for confounders.
  
  
  CONCLUSIONS
  Early adulthood is an additional critical phase for daily smoking initiation. The clear and consistent negative association between SES and late-onset smoking, as well as the positive association between SES and smoking cessation, contribute to the association between SES and smoking in the general adult population.
authors.affiliation: Uni Health, Bergen, Norway. tore.tjora@uni.no
authors.forename: Tore
authors.initials: T
authors.lastname: Tjora
authors.forename: Jørn
authors.initials: J
authors.lastname: Hetland
authors.forename: Leif Edvard
authors.initials: LE
authors.lastname: Aarø
authors.forename: Bente
authors.initials: B
authors.lastname: Wold
authors.forename: Simon
authors.initials: S
authors.lastname: Øverland
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D017668:Age of Onset; D005260:Female; D005500:Follow-Up Studies; D015438:Health Behavior; D006801:Humans; D008297:Male; D009664:Norway / Q000453:epidemiology; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology* / Q000523:psychology*; D016540:Smoking Cessation / Q000706:statistics & numerical data*; D012923:Social Class; D055815:Young Adult