Dietary inflammatory index and number of functional teeth in middle-aged and older Japanese adults: A cross-sectional study using national survey data

Purpose: To determine whether the number of functional teeth, including the remaining natural teeth and prosthetically restored missing teeth, is associated with the dietary inflammatory index (DII), a quantitative measure of the inflammatory potential of the overall diet, in middle-aged and older Japanese adults. Methods: National survey data from a non-institutionalized Japanese population aged >_45 years was analyzed. Multivariable linear regression analyses were performed to assess the association between the DII score, which was calculated based on dietary records, and the number of functional teeth, which was determined during dental examination. All regression analyses were stratified according to the age groups 45-64, 65-74, and >_75 years. The association between functional tooth units (FTUs) and the DII was assessed using sensitivity analysis. Results: In total, 2407 individuals (1053 men and 1354 women; mean age = 66.7 years) were included. Multivariable analysis revealed that the number of functional teeth was significantly inversely associated with the DII score among participants aged >= 75 years (regression coefficient per increase of one in the number of functional teeth = -0.050; 95% confidence interval = -0.089 to -0.010). The number of functional teeth was not associated with the DII score in younger age categories (i.e., those aged 45-74 years). As in the primary analysis, the number of FTUs was significantly inversely associated with the DII score only in the group aged >= 75 years. Conclusions: A greater number of functional teeth was associated with a lower DII (i.e., diet with greater anti-inflammatory potential) in Japanese adults aged >= 75 years.