title: Heaviness of smoking predicts smoking relapse only in the first weeks of a quit attempt: findings from the International Tobacco Control Four-Country Survey.
abstract: BACKGROUND
  The Heaviness of Smoking Index (HSI) is the measure of dependence most strongly predictive of relapse. However, recent research suggests it may not be predictive of longer-term relapse. Our aim was to examine its predictive power over the first 2 years after quitting and explore whether use of stop-smoking medications is a moderator.
  
  
  METHODS
  Data (n = 7,093) came from the first 7 waves (2002-2009) of the International Tobacco Control Four-Country Survey, an annual cohort survey of smokers in Canada, the United States, the United Kingdom, and Australia. HSI and its 2 components (cigarettes per day [CPD] and time to first cigarette [TTFC]) were used to predict smoking relapse risk in the 2 years after the start of a quit attempt.
  
  
  RESULTS
  Scores on HSI and its components all strongly predicted relapse, but there was an interaction with time (p < .001). These measures were strong predictors of relapse within the first week of quitting (hazard ratios [HR] = 1.17, 1.24, and 1.30 for HSI, CPD, and TTFC, respectively; all p < .001), less predictive of relapse occurring between 1 week and 1 month, and not clearly predictive beyond 1 month. Among those using medication to quit, hazard ratio for HSI (HR = 1.11, p < .001) was significantly lower than for those not using (HR = 1.24, p < .001) in the first week but not beyond.
  
  
  CONCLUSIONS
  HSI and its 2 components are strong predictors of short-term smoking relapse, but they rapidly lose predictive power over the first weeks of an attempt, becoming marginally significant at around 1 month and not clearly predictive beyond then.
authors.affiliation: VicHealth Centre for Tobacco Control, Cancer Council Victoria, Carlton, Australia;
authors.forename: Hua-Hie
authors.initials: HH
authors.lastname: Yong
authors.forename: Ron
authors.initials: R
authors.lastname: Borland
authors.forename: James
authors.initials: J
authors.lastname: Balmford
authors.forename: Andrew
authors.initials: A
authors.lastname: Hyland
authors.forename: Richard J
authors.initials: RJ
authors.lastname: O'Connor
authors.forename: Mary E
authors.initials: ME
authors.lastname: Thompson
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Spittal
mesh_terms: D000293:Adolescent; D000328:Adult; D001315:Australia; D002170:Canada; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012008:Recurrence; D012907:Smoking / Q000453:epidemiology*; D016540:Smoking Cessation / Q000706:statistics & numerical data*; D000074606:Smoking Prevention; D062789:Tobacco Products; D014029:Tobacco Use Disorder / Q000453:epidemiology / Q000517:prevention & control; D006113:United Kingdom; D014481:United States; D055815:Young Adult