title: Evaluation of a Novel Difficulty of Smoking Cessation Phenotype Based on Number of Quit Attempts.
abstract: BACKGROUND
  Numerous studies have sought to identify genes that influence the ability to quit smoking, but none found any that are consistently associated with smoking cessation.
  
  
  METHODS
  We developed a novel difficulty of quitting smoking phenotype based on the extremes of the number of quit attempts needed to achieve successful abstinence: Easy quitters were defined as having achieved long-term (>1 year) abstinence after their first quit attempt and difficult quitters as having reported 10 or more quit attempts. We conducted a two-stage study to determine if this phenotype could be useful for identifying single nucleotide polymorphisms (SNPs) that influence smoking cessation. In stage 1, 82 SNPs in 26 genes involved in nicotine signaling and metabolism were genotyped in 1357 easy quitters and 1321 difficult quitters from Cancer Prevention Study 3 (CPS-3). In stage 2, the 11 SNPs associated with difficult quitting in stage 1 (p < .1) were genotyped in an independent sample of 1300 easy quitters and 1299 difficult quitters from CPS-3.
  
  
  RESULTS
  Three of 11 SNPs (HTR1B rs6298, NR4A2 rs834829, and CYP2A65 rs8192729) were significantly associated with the difficult quitting phenotype in stage 2 (p < .05). In addition, a polygenic risk score based on the 11 SNPs identified in stage 1 was significantly associated with the difficult quitting phenotype in stage 2 (odds ratio = 1.08, 95% confidence interval: 1.03-1.14 per quintile, p trend = 4.5×10-3).
  
  
  CONCLUSIONS
  Using a novel difficulty of quitting phenotype, three gene variants and a polygenic risk score based on 11 SNPs were found to be significantly associated with smoking cessation.
  
  
  CONCLUSIONS
  Our results provide evidence that a difficulty of quitting smoking phenotype based on the extremes of number of quit attempts could be a useful tool for identifying genetic variants that influence difficulty of smoking cessation. Knowledge of these genetic variants will indicate biological pathways that could be targeted for the development of novel smoking cessation aids and could be used to determine which smokers are most likely to benefit from such smoking cessation aids.
authors.affiliation: Epidemiology Research Program, American Cancer Society, Atlanta, GA.
authors.forename: Victoria L
authors.initials: VL
authors.lastname: Stevens
authors.affiliation: Epidemiology Research Program, American Cancer Society, Atlanta, GA.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Jacobs
authors.affiliation: Epidemiology Research Program, American Cancer Society, Atlanta, GA.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Gapstur
authors.affiliation: Epidemiology Research Program, American Cancer Society, Atlanta, GA.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Carter
authors.affiliation: Epidemiology Research Program, American Cancer Society, Atlanta, GA.
authors.forename: Mia M
authors.initials: MM
authors.lastname: Gaudet
authors.affiliation: Behavioral Research Center, American Cancer Society, Atlanta, GA.
authors.forename: J Lee
authors.initials: JL
authors.lastname: Westmaas
authors.affiliation: Epidemiology Research Program, American Cancer Society, Atlanta, GA.
authors.forename: Alpa V
authors.initials: AV
authors.lastname: Patel
mesh_terms: D006801:Humans; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D012907:Smoking / Q000453:epidemiology / Q000235:genetics / Q000628:therapy; D016540:Smoking Cessation / Q000706:statistics & numerical data*