**Background:** Frailty is a growing global health burden as populations age, affecting 12–24% of older adults and increasing risks of morbidity, mortality, and healthcare costs. Nutrition is a modifiable factor in frailty development, but most studies focus on single nutrients or foods rather than overall dietary patterns. Dietary diversity—the number of different food groups consumed—ensures adequate macronutrient and micronutrient intake. This study aimed to prospectively assess the association between dietary diversity score (DDS) and frailty incidence in Chinese older adults.
**Methods:** Data were drawn from the Chinese Longitudinal Healthy Longevity Survey (CLHLS), a nationwide prospective cohort of community-dwelling older adults conducted across 23 counties/cities covering 85% of China's population. The analysis used data from 2011–2014. From 9,765 baseline participants (2011–2012), exclusions were made for age <65 years (n=86), frailty at baseline (n=1,570), missing frailty data (n=4,522), missing DDS data (n=16), and loss to follow-up or death, yielding a final sample of 1,948 non-frail older adults. Frailty was assessed using a 44-item frailty index (FI), with frailty defined as FI > 0.21. DDS was calculated from a food frequency questionnaire covering 11 food groups (meat, fish, eggs, beans, mushrooms/algae, tea, garlic, milk products, nuts, fresh vegetables, fresh fruits), with scores ranging 0–11. Participants were divided into low and high DDS groups by median score. Changes in dietary diversity (CDD) from 2011–2014 were categorized as consistently low, declining, improving, or consistently high. Generalized Estimating Equations (GEE) estimated risk ratios (RRs) and 95% confidence intervals (CIs), with progressive adjustment: Model 1 (unadjusted), Model 2 (age and sex), Model 3 (fully adjusted for age, sex, residential location, education, BMI, drinking, smoking, exercise, marital status, financial support, and chronic disease history). Stratified analyses by age (65–79 vs. ≥80 years) and residential location (urban vs. town/rural) were conducted. Sensitivity analyses included retaining participants with ≤5 missing health deficits and excluding those with pre-frailty at baseline.
**Key Results:** The sample included 1,948 participants (53.4% male, 46.6% female); 43.0% were aged ≥80 years, 79.6% lived in town/rural areas, 48.2% were married, 44.3% had informal education, and 38.9% were financially independent. Mean DDS was 5.7 (SD 1.8). Over 3 years, 381 participants (19.56%) developed frailty. In the fully adjusted model (Model 3), high DDS was associated with a 28% lower risk of frailty compared to low DDS (RR 0.72; 95% CI: 0.57–0.91). As a continuous variable, each unit increase in DDS reduced frailty risk by 12% (RR 0.88; 95% CI: 0.82–0.94). For CDD, compared to consistently low DDS, consistently high DDS showed a 44% lower frailty risk (RR 0.56; 95% CI: 0.42–0.74) in the fully adjusted model. Improving dietary diversity (RR 0.79; 95% CI: 0.56–1.11) and declining diversity (RR 0.94; 95% CI: 0.67–1.33) were not statistically significant. In stratified analysis, consistently high DDS reduced frailty risk for those aged 65–79 years (RR 0.46; 95% CI: 0.33–0.64) and those in town/rural areas (RR 0.46; 95% CI: 0.33–0.64), but not for those aged ≥80 years (RR 1.00; 95% CI: 0.56–1.80) or urban residents (RR 1.38; 95% CI: 0.48–3.93). Among individual food groups, inverse associations with frailty were found for meat (RR 0.47; 95% CI: 0.32–0.68), fish (RR 0.56; 95% CI: 0.39–0.80), beans (RR 0.68; 95% CI: 0.47–0.97), nuts (RR 0.59; 95% CI: 0.40–0.87), fresh fruits (RR 0.69; 95% CI: 0.49–0.97), and fresh vegetables (RR 0.25; 95% CI: 0.14–0.45). Sensitivity analyses confirmed the robustness of these findings.
**Clinical Implications:** This study provides prospective evidence that higher dietary diversity is associated with reduced frailty risk in Chinese older adults, with the strongest protection from consistently high diversity over time. The protective effect was most pronounced in younger older adults (65–79 years) and those in town/rural areas, suggesting these groups may benefit most from dietary interventions. The findings support public health strategies promoting diverse diets—including meat, fish, beans, nuts, fruits, and vegetables—to prevent or delay frailty. Limitations include potential recall bias from self-reported food frequency data, lack of quantitative intake measurement, and possible selection bias from differential loss to follow-up. Further research is needed to confirm these associations in other populations and to explore underlying mechanisms.