The Dietary Inflammatory Index and Periodontal Inflammation in Community‐Dwelling Older Adults in Japan: The Otassha Study

ABSTRACT Aim To investigate the association between the dietary inflammatory index (DII) and periodontal inflammation (periodontal inflamed surface area [PISA]) in community‐dwelling older adults in Japan. Materials and Methods DII scores, derived from a validated questionnaire‐based dietary assessment, were categorised into quartiles. Linear regression models were used to assess the associations between DII (exposure) and log‐transformed PISA (outcome) calculated from full‐mouth periodontal examinations. Restricted cubic spline (RCS) models were applied to examine potential nonlinearity. Results Among the 466 participants (mean age = 73.1 years), the median PISA was 37.8 mm 2 , and the median values for whole‐mouth average probing pocket depth, clinical attachment loss and bleeding on probing were 1.8 mm, 2.0 mm and 3.3%, respectively. After adjustment for covariates, participants in the third [regression coefficient (95% confidence interval) = 0.49 (0.03–0.95)] and fourth [0.83 (0.34–1.32)] DII quartiles had significantly higher PISA values. Although the test for nonlinearity was not significant, the RCS analysis revealed a largely flat association below DII ≈ −1.5, followed by a near‐linear increase with increasing DII. Conclusions Diets with greater inflammatory potential were associated with higher periodontal inflammatory burdens among older adults in Japan. DII may serve as a modifiable dietary indicator to support periodontal health in ageing populations.