Tooth loss, body mass index and cognitive function among middle-aged and older adults in China: Does gender matter?

Background: Previous studies have shown a longitudinal association between tooth loss and cognitive function. Body mass index (BMI) is an essential applicable indicator of health status screening. However, the underlying mechanism among these factors remains unclear. This study aimed to determine the mediating role of BMI in the tooth loss-cognition relationship by gender among Chinese middle-aged and older adults. Methods: This is a prospective and cohort study. We used three waves of follow-up data (2011, 2013, and 2015) from the China Health and Retirement Longitudinal Survey, including 10,013 participants aged 45 years or above. Cognitive function was evaluated by Telephone Interview of Cognitive Status, words recall, and figure drawing. The cross-lagged panel model was applied to test the hypothesized model. Results: Tooth loss is associated with higher BMI and lower level of cognitive function. We found significant total effects (B =-0.017, P = 0.008), direct effect (B =-0.015, P = 0.022) and indirect effects (B =-0.002, P = 0.010) of tooth loss on cognition mediated through BMI only among middle-aged and older men. For middle-aged and older women, the total effect (B =-0.010, P = 0.125) and direct effect (B =-0.007, P = 0.249) were no more significant. Conclusions: The longitudinal association between tooth loss and cognition was primarily indirect through BMI among middle-aged Chinese males but not women. Public health authorities should remind middle-aged and older males with tooth loss and high BMI to participate in timely medical checkups for improving cognition.