Validity and feasibility of the simplified dietary inflammatory index in Chinese older adults

Chronic low-grade systemic inflammation contributes to chronic diseases. The dietary inflammatory index (DII) is a validated tool for quantifying diet-related inflammation; however, its assessment methods are limited. This study developed a simplified DII (S-DII) based on a 25-item food frequency questionnaire (FFQ25). To validate the S-DII, we evaluated 269 community-dwelling older adults in China. Dietary intake data were measured using the FFQ25 and 24-h dietary recall (24HR). Fasting blood samples were collected to quantify inflammatory markers, including C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), interleukin (IL)-4, IL-6, IL-10, and IL-1β. To examine applicability, an additional 983 older adults were recruited. The S-DII demonstrated moderate concordance with the DII calculated from 24HR data (r = 0.640, intraclass correlation coefficient = 0.615, p < 0.05) and was supported by Bland-Altman analysis. CRP and IL-1β were positively associated with the S-DII after controlling covariates, whereas no significant associations were found for S-DII with TNF-α, IL-4, IL-6, or IL-10. In the larger cohort (n = 983), intake of cereals, tubers, red meat, poultry, soybeans, nuts, vegetables, and fruits was significantly higher among adults with the lowest S-DII values, while dairy and egg consumption showed an inverse trend (p < 0.05). Higher S-DII scores were significantly associated with higher odds of hypertension and coronary heart disease after covariate adjustment. The S-DII demonstrated strong validity and feasibility as an assessment tool for diet-related inflammation. These preliminary findings indicated that the S-DII could serve as a time-efficient screening tool for dietary inflammatory potential, assisting targeted nutritional prevention of chronic diseases among community-dwelling older adults with similar regional characteristics.