title: The interactive association of smoking and drinking levels with presence of periodontitis in South Korean adults.
abstract: BACKGROUND
  Periodontitis is a chronic and long-lasting low-grade inflammatory disease. Numerous studies have shown that the severity of periodontitis rose when there was an increase in the amount of smoking or alcohol consumption. However, as periodontitis known as a chronic disease, it is important to consider not only the amount but "duration" with frequency i.e., rates, of smoking or drinking. This study assessed impacts of the amount and duration of smoking and drinking on periodontal health in Korean adults. We also investigated whether or not there is an interactive effect of smoking and drinking on periodontal health.
  
  
  METHODS
  Under a cross-sectional study design, we used data from the fourth and fifth the Korean National Health and Nutrition Examination Survey (KNHANES) sessions (2008-2010). A total of 18,488 subjects (over 19 years) answered both smoking and drinking status and were given the periodontal examination. Periodontal health status was determined by the community periodontal index (CPI) developed by the World Health Organization (WHO). According to the WHO guidelines, if a participant's CPI was 3 or larger, we classified the person as a case of periodontitis. Participants with a CPI < 3 were assigned to the control group.
  
  
  RESULTS
  Prevalence of periodontitis for self-reported smokers or drinkers in South Korea was 35.0 or 28.0 %, respectively. We observed 1.20 (0.93~1.56) of odds ratio (95 % CI) for prevalence (POR) of periodontitis for those smoked <13 pack-year (PY) and drank ≥6.8 glass-year (GY). And we had POR of 1.91 (1.34~2.73) for those smoked ≥13 PY and drank <6.8 GY, compared to those nonsmoking nondrinkers. The observed POR of 2.41 (95 % CI: 1.94-3.00), for those smoked ≥13 PY and drank ≥6.8 GY, was higher than a multiplicative effect estimated, i.e., 1.20 (0.93~1.56) [those smoked <13 PY and drank ≥6.8 GY] × 1.91 (1.34~2.73) [those smoked ≥13 PY and drank <6.8 GY], or 2.29.
  
  
  CONCLUSIONS
  We observed a multiplicative interactive effect of smoking and drinking on periodontal status among Korean adults.
authors.affiliation: Department of Environmental Health Sciences, Soonchunhyang University, Soonchunhyang-Ro 22, Asan, Chungnam, 336-745, South Korea.
authors.forename: Mira
authors.initials: M
authors.lastname: Lee
authors.affiliation: Graduate School of Medicine, Gachon University, Incheon, South Korea.
authors.forename: Yoon-Hyeong
authors.initials: YH
authors.lastname: Choi
authors.affiliation: Preventive Medicine and Public Health, College of Medicine, Yeungnam University, Daegu, South Korea.
authors.forename: Jun
authors.initials: J
authors.lastname: Sagong
authors.affiliation: Department of Environmental Health Sciences, Soonchunhyang University, Soonchunhyang-Ro 22, Asan, Chungnam, 336-745, South Korea.
authors.forename: Sol
authors.initials: S
authors.lastname: Yu
authors.affiliation: Department of Preventive Medicine, Soonchunhyang University, Cheonan, South Korea.
authors.forename: Yongbae
authors.initials: Y
authors.lastname: Kim
authors.affiliation: Department of Environmental Health Sciences, Soonchunhyang University, Soonchunhyang-Ro 22, Asan, Chungnam, 336-745, South Korea.
authors.forename: Dongjae
authors.initials: D
authors.lastname: Lee
authors.affiliation: Department of Environmental Health Sciences, Soonchunhyang University, Soonchunhyang-Ro 22, Asan, Chungnam, 336-745, South Korea. sungroul.kim@gmail.com.
authors.forename: Sungroul
authors.initials: S
authors.lastname: Kim
mesh_terms: D000328:Adult; D000428:Alcohol Drinking; D003430:Cross-Sectional Studies; D006801:Humans; D009749:Nutrition Surveys; D010518:Periodontitis / Q000453:epidemiology*; D056910:Republic of Korea / Q000453:epidemiology; D012907:Smoking
keywords: Drinking; Interaction; Periodontitis; Smoking