Association of Number of Teeth with Cognitive and Physical Functions in Japanese Older Adults: A Cross-sectional Study

Abstract

The relationship of the number of teeth with cognitive, physical, and oral functions in older adults has been widely investigated, but there are few studies with a cutoff of more than 20 and less than 20 teeth. This cross-sectional study examined the association of ≥ 20 teeth with physical and cognitive assessment scores, oral function, and subjective health status among older adults. Participants were 754 community-dwelling Japanese aged ≥ 65 years. Mean age was 78.5 ± 5.6 years and 21.6% were men. The following assessments were performed: handgrip strength, balance test, 5-m walk test, timed up and go test, Yamaguchi Kanji-Symbol Substitution Test (YKSST), repetitive saliva swallowing test (RSST), stretch cheek test, oral diadochokinesis test, chewing strength test, number of remaining teeth, and subjective health status. There were 328 participants aged ≥ 80 years (43.5%), and 52.4% of them (n = 172) retained ≥ 20 teeth. Participants with ≥ 20 teeth had significantly better scores on the balance test, stretch cheek test, and YKSST, better masticatory strength, and a lower RSST score compared with those with < 20 teeth, after controlling for age and sex. Stepwise logistic regression analysis showed that having ≥ 20 remaining teeth was associated with younger age (OR = 0.967, P = 0.036), better balance test (OR = 1.010, P = 0.009), YKSST score (OR = 1.031, P < 0.001), and masticatory strength (OR = 1.252, P = 0.004). These findings suggest that older adults with ≥ 20 teeth have better cognitive, physical, and oral functions than those with fewer teeth.