title: Reexamining the association between smoking and periodontitis in the dunedin study with an enhanced analytical approach.
abstract: BACKGROUND
  Smoking is a major risk factor for periodontal disease. Conventional oral epidemiology approaches have found strong, consistent associations between chronic smoking and periodontal attachment loss (AL) through ages 26, 32, and 38 years, but those statistical methods disregarded the data's hierarchical structure. This study reexamines the association using hierarchical modeling to: 1) overcome the limitations of an earlier approach (trajectory analysis) to the data and 2) determine the robustness of the earlier inferences.
  
  
  METHODS
  Periodontal examinations were conducted at ages 26, 32, and 38 years in the Dunedin Multidisciplinary Health and Development Study. The number of participants examined at those three ages were 913, 918, and 913, respectively. A generalized linear mixed model with a quasi-binomial approach was used to examine associations between chronic smoking and periodontal AL.
  
  
  RESULTS
  At ages 26, 32, and 38, smokers had 3.5%, 12.8%, and 23.2% greater AL than non-smokers. Regular cannabis use was associated with greater AL after age 32, but not at age 26. Males had more AL than females. Participants with high plaque scores had consistently greater AL; those who were of persistently low socioeconomic status had higher AL at ages 32 and 38, but not at age 26. The amount of AL in anterior teeth was less than in premolars and molars. Gingival bleeding was associated with higher AL at ages 26, 32, and 38.
  
  
  CONCLUSIONS
  The smoking-periodontitis association is observable with hierarchical modeling, providing strong evidence that chronic smoking is a risk factor for periodontitis.
authors.affiliation: Department of Oral Sciences, Sir John Walsh Research Institute, School of Dentistry, The University of Otago, Dunedin, New Zealand.
authors.forename: Jiaxu
authors.initials: J
authors.lastname: Zeng
authors.forename: Sheila M
authors.initials: SM
authors.lastname: Williams
authors.forename: David J
authors.initials: DJ
authors.lastname: Fletcher
authors.forename: Claire M
authors.initials: CM
authors.lastname: Cameron
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Broadbent
authors.forename: Dara M
authors.initials: DM
authors.lastname: Shearer
authors.forename: W Murray
authors.initials: WM
authors.lastname: Thomson
mesh_terms: D000328:Adult; D000367:Age Factors; D000465:Algorithms; D015331:Cohort Studies; D003742:Dental Devices, Home Care / Q000706:statistics & numerical data; D003773:Dental Plaque / Q000453:epidemiology; D005260:Female; D005884:Gingival Hemorrhage / Q000453:epidemiology; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D008385:Marijuana Smoking / Q000453:epidemiology; D015233:Models, Statistical; D009520:New Zealand / Q000453:epidemiology; D017622:Periodontal Attachment Loss / Q000453:epidemiology; D010518:Periodontitis / Q000453:epidemiology*; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000453:epidemiology*; D012923:Social Class
keywords: Cannabis; cohort studies; multilevel analysis; periodontal diseases; risk factors; smoking