Periodontitis was reported to be associated with chronic obstructive pulmonary disease (COPD), and both diseases are related to smoking. To identify associations between periodontitis, smoking, and COPD, this cross-sectional study enrolled 1474 Japanese men (mean age 55.2 ± 8.9 years) surveyed between 2003 and 2006. Periodontal status was evaluated by using the community periodontal index. Periodontitis was defined as the presence of at least one sextant with a pocket depth ≥4 mm. Lung function was measured by spirometry, and COPD was defined as ratio of forced expiratory volume after 1 second to forced vital capacity of <0.70. Logistic regression analysis showed that the association between COPD and smoking was stronger for men with periodontitis (odds ratio 2.45; 95% confidence interval 1.37-4.37) than for those without periodontitis (odds ratio 1.64; 95% confidence interval 0.91-2.94), after adjusting for age, number of present teeth, body mass index, alcohol intake, occupation, hypertension, and diabetes. The association between smoking and COPD was significant for men with periodontitis but was weaker for those without periodontitis. These findings suggest that periodontitis modifies the association between smoking and COPD.
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