Dietary Inflammatory Potential and Continence-Related Symptoms: Cross-Sectional and Longitudinal Analyses of Three Population Studies

Dietary inflammatory potential has been associated with prevalent continence problems, but cross-population comparability and prospective associations remain uncertain. We examined these questions in three population studies. Repeated cross-sectional analyses of the National Health and Nutrition Examination Survey (NHANES) 2005-2010 related a 25-component Dietary Inflammatory Index (DII) to monthly mucus, liquid, or solid leakage. A 15-component DII enabled a partially harmonized comparison with the English Longitudinal Study of Aging (ELSA). The Chinese Longitudinal Healthy Longevity Survey (CLHLS) 2008-2018 used a 13-food directional score and combined urinary and bowel continence impairment. Analyses included logistic regression, splines, repeated measures, and sensitivity checks for dietary measurement, weighting, and missing covariates. Among 13,385 NHANES participants, each DII unit was associated with prevalent leakage (odds ratio 1.075, 95% confidence interval 1.029-1.124), with similar estimates across survey periods. Concurrent estimates were 1.136 (1.066-1.210) per 15-component DII unit in ELSA and 1.440 (1.135-1.828) per score standard deviation in CLHLS. Combined weighting in ELSA and cognitive adjustment in CLHLS attenuated the estimates, with intervals including the null. Cumulative incident estimates were 0.974 (0.902-1.051) in ELSA and 1.044 (0.920-1.184) in CLHLS, using the respective exposure units. Concurrent associations were observed in the main analyses, but baseline scores showed no clear associations with incident outcomes. Dietary measurement differences, symptom-related dietary changes, and functional or socioeconomic confounding limit interpretation. These findings extend cross-sectional evidence without establishing that lowering dietary inflammatory potential prevents continence-related symptoms.