Background: The principal objectives of this study were to examine the relationship between cigarette smoking and periodontitis and to estimate the proportion of periodontitis in the United States adult population that is attributable to cigarette smoking.

Methods: Data were derived from the Third National Health and Nutrition Examination Survey, a nationally representative multipurpose health survey conducted in 1988 to 1994. Participants were interviewed about tobacco use and examined by dentists trained to use standardized clinical criteria. Analysis was limited to dentate persons aged > or =18 years with complete clinical periodontal data and information on tobacco use and important covariates (n = 12,329). Data were weighted to provide U.S. national estimates, and analyses accounted for the complex sample design. We defined periodontitis as the presence of > or =1 site with clinical periodontal attachment level > or =4 mm apical to the cemento-enamel junction and probing depth > or =4 mm. Current cigarette smokers were those who had smoked > or =100 cigarettes over their lifetime and smoked at the time of the interview; former smokers had smoked > or =100 cigarettes but did not currently smoke; and never smokers had not smoked > or =100 cigarettes in their lifetime.

Results: We found that 27.9% (95% confidence interval [CI]: +/-1.8%) of dentate adults were current smokers and 23.3% (95% CI: +/-1.2%) were former smokers. Overall, 9.2% (95% CI: +/-1.4%) of dentate adults met our case definition for periodontitis, which projects to about 15 million cases of periodontitis among U.S. adults. Modeling with multiple logistic regression revealed that current smokers were about 4 times as likely as persons who had never smoked to have periodontitis (prevalence odds ratio [ORp] = 3.97; 95% CI, 3.20-4.93), after adjusting for age, gender, race/ethnicity, education, and income:poverty ratio. Former smokers were more likely than persons who had never smoked to have periodontitis (ORp = 1.68; 95% CI, 1.31-2.17). Among current smokers, there was a dose-response relationship between cigarettes smoked per day and the odds of periodontitis (P <0.000001), ranging from ORp = 2.79 (95% CI, 1.90-4.10) for < or =9 cigarettes per day to ORp = 5.88 (95% CI, 4.03-8.58) for > or =31 cigarettes per day. Among former smokers, the odds of periodontitis declined with the number of years since quitting, from ORp = 3.22 (95% CI, 2.18-4.76) for 0 to 2 years to ORp = 1.15 (95% CI, 0.83-1.60) for > or =11 years. Applying standard epidemiologic formulas for the attributable fraction for the population, we calculated that 41.9% of periodontitis cases (6.4 million cases) in the U.S. adult population were attributable to current cigarette smoking and 10.9% (1.7 million cases) to former smoking. Among current smokers, 74.8% of their periodontitis was attributable to smoking.

Conclusions: Based on findings from this study and numerous other reports, we conclude that smoking is a major risk factor for periodontitis and may be responsible for more than half of periodontitis cases among adults in the United States. A large proportion of adult periodontitis may be preventable through prevention and cessation of cigarette smoking.