A comprehensive index for the modeling of smoking history in periodontal research.

Cigarette smoking is both a strong and common risk factor for chronic periodontitis. It is a multi-dimensional exposure that is difficult to model accurately. We propose a new comprehensive smoking index (CSI) that accounts for intensity, duration, and recency of smoking and allows for estimation of the half-life of the smoking effect. Using NHANES III data from 12,623 subjects aged 20+ yrs, we compared the performance of the CSI with that of various conventional approaches using multiple logistic regression models of chronic periodontitis. The estimate of the smoking effect's half-life was 1.5 yrs (95% CI, 0.5-2.5 yrs). Use of the new index resulted in best model fit and the highest Wald statistic for the smoking effect on chronic periodontitis. The results suggest that use of the CSI may be a more comprehensive, efficient, and parsimonious approach to the modeling of smoking history in periodontal research.