Influence of the number of teeth on the cognitive function of older adults: an intermediary analysis based on dietary diversity.

Tooth loss has been associated with cognitive function in older adults. We aimed to explore the mechanism between tooth loss and cognitive decline in these specific populations, which has been scarcely studied. This study used the Longitudinal data of the Chinese Longitudinal Healthy Longevity Survey (CLHLS) to build a linear mixed effects model to explore the impact of tooth loss on cognitive function in older adults. The effect of wearing dentures on the above effects was also evaluated. In addition, through mediation analysis, this study studied the mediating role of dietary diversity in the relationship between tooth loss and cognitive function. A total of 8283 older adults aged ≥65 years were included in this study. Maintaining ≥20 teeth was associated with better cognitive function (β = 0.338, 95% confidence interval [CI]: 0.229∼0.447), and so was denture wearing (β = 0.449, 95%CI: 0.351∼0.547). However, there was no significant difference in cognitive function between the older adults with < 20 teeth and dentures and those with ≥20 teeth (β = 0.084, 95%CI: -0.035∼0.203). The total effect and direct effect of tooth number on cognitive function were 0.201 (95%CI: 0.096-0.306) and 0.177 (95%CI: 0.072-0.282), respectively. The indirect effect of dietary diversity was 0.023 (95% CI: 0.010∼0.037), accounting for 11.65% of the total effect. In Chinese older adults, more teeth were associated with better cognitive function. Denture wearing reduced the risk of cognitive decline caused by tooth loss to a certain extent. Dietary diversity mediated the relationship between tooth number and cognitive function.