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Spiekerman CF, Hujoel PP et al. J Dent Res 2003; 82: 345–349

One current problem in numerous studies purporting to give evidence of systemic effects arising from chronic periodontal diseases is that tobacco may be a causal factor common to both. Merely including smoking in the analysis is insufficient, since the quality of this datum may be inadequate for identifying causality.

This study used serum cotinine, an objective measure of current tobacco exposure, to evaluate self-reported current smoking in relation to periodontal attachment loss in a cohort of 1507 participants in the large US Third National Health and Nutrition Examination Survey.

Unadjusted correlations of cotinine with log cigarettes smoked and mean attachment loss were 0.5 and 0.17 respectively. However, a regression model adjusted for self-reported current smoking still indicated a significant correlation between serum cotinine and mean attachment loss. The authors consider that this bias may contribute to the reported associations between periodontitis and smoking related systemic diseases.