Number of Teeth and Dementia-free Life Expectancy: A 10-Year Follow-Up Study from the Japan Gerontological Evaluation Study.

ABSTRACT

OBJECTIVES: Previous studies have reported that tooth loss is associated with an increased risk of dementia; however, few have explored the association between number of teeth and dementia-free and total life expectancies. We investigated whether having more teeth is associated with longer dementia-free and total life expectancies. DESIGN: A 10-year follow-up prospective cohort study from 2010 to 2020. SETTING AND PARTICIPANTS: Functionally independent older adults aged ≥65 years living in 9 municipalities in Japan. METHODS: The exposure was the number of teeth (≥20, 10-19, 1-9, and 0). Dementia onset and mortality within the 10-year follow-up were used as the outcome. Dementia-free and total life expectancies according to the number of teeth were derived from multistate modeling estimates. RESULTS: A total of 44,083 participants were included (men 46.8%). The mean age was 73.7 years [standard deviation (SD) = 6.0]. During follow-up, 17.3% and 21.4% of the participants experienced the onset of dementia and death, respectively. Having fewer teeth was associated with dementia [hazard ratio (HR), 1.14; 95% confidence interval (CI), 1.07-1.22, 10-19 teeth; HR, 1.15; 95% CI, 1.08-1.22, 1-9 teeth; HR, 1.13; 95% CI, 1.05-1.21, 0 teeth] and death (HR, 1.13; 95% CI, 1.05-1.22, 10-19 teeth; HR, 1.27; 95% CI, 1.19-1.37, 1-9 teeth; HR, 1.47; 95% CI, 1.36-1.59, 0 teeth) compared with having ≥20 teeth. Dementia-free life expectancies at the age of 65 years were 16.43 years and 18.88 years with ≥20 teeth, and 14.40 years and 17.12 years with 0 teeth for men and women, respectively. The total life expectancies at the age of 65 were 17.84 years and 22.03 years with ≥20 teeth, and 15.42 years and 19.79 years with 0 teeth for men and women, respectively. CONCLUSIONS AND IMPLICATIONS Having more teeth was associated with longer dementia-free and total life expectancies.