Effect of smoking on periodontal health and validation of self-reported smoking status with serum cotinine levels

To investigate whether self-reported smoking and serum cotinine levels associate with periodontal pocket development and to determine the accuracy of self-reported smoking using serum cotinine. This 4-year prospective cohort study included data from 294 dentate adults, aged ≥30 years, who participated in both the Health 2000 Survey and the Follow-up Study of Finnish Adults’ Oral Health. Subjectively reported smoking status (daily smokers <i>n</i> = 62, occasional smokers <i>n</i> = 12, quitters <i>n</i> = 49, and never-smokers <i>n</i> = 171), serum cotinine levels, demographic factors, education level, dental behaviours and medical history were collected at baseline. The outcome measure was the number of teeth with periodontal pocketing ≥4 mm over 4 years. Self-reported daily smokers had 1.82 (95% CI: 1.32–2.50) higher incidence of deepened periodontal pockets than never-smokers. A positive association was observed between serum cotinine (≥42.0 μg/L) and the development of periodontal pockets. The misclassification rate of self-reported smoking was 6%. Both self-reported daily smoking and higher serum cotinine were associated with periodontal pocket development. Self-reported smoking was fairly accurate in this study. However, higher cotinine levels among a few self-reported never-smokers indicated misreporting or passive smoking. Thus, self-reports alone are not enough to assess the smoking-attributable disease burden.