Fig. 2

Association between the number of natural teeth and mortality. The results were based on addictive cox regression taking number of natural teeth as a smoothing term in the model. The inflection point with lowest hazard (28 teeth) was considered the reference. The addictive cox regression model has adjusted for age, sex, residence, denture use, education, sufficient income for daily needs, living arrangement, BMI, smoking, alcohol drinking, frequent vegetable consumption, frequent fruit consumption, impaired activity of daily living, cognitive impairment, hypertension, self-reported history of diabetes mellitus, self-reported history of heart disease, self-reported history of cerebrovascular disease, and self-reported history of respiratory diseases. The minimum number of natural teeth showing no significantly increased risk was 25 (HR for 24 teeth: 1.05, 95%CI 1.00 to1.10, P = 0.05; HR for 25 teeth: 1.03, 95%CI 0.99 to 1.08, P = 0.18)