To investigate the association between the Geriatric Nutritional Risk Index(GNRI) and metabolic syndrome(MS) among elderly people of ethnic minorities in Guizhou Province, providing scientific evidence for the health management of the elderly in this region.

Based on the “Southwest Regional Cohort Study of Natural Populations of Ethnic Minorities”, this study included 4 521 elderly individuals aged 60 and above from the Miao, Dong, and Bouyei ethnic groups in Guizhou Province. Data on demographic characteristics, lifestyle, physical examination, and biochemical indicators were collected. Logistic regression, subgroup analyses, and restricted cubic splines (RCS) were used to evaluate the association between GNRI and MS. Within each ethnic group, the optimal cut-offs from ROC curves (107.9 for the overall population, 108.0 for the Miao, 110.1 for the Dong, and 106.0 for the Bouyei) were applied to categorize GNRI into high and low levels for subsequent sensitivity analyses.

The overall prevalence of MS was 23.9%, with prevalence rates of 24.6%, 25.4%, and 21.3% among the Miao, Dong, and Bouyei ethnic groups, respectively. In Model 3, which adjusted for all covariates, GNRI as a continuous variable was positively correlated with MS risk in the total population, Miao, and Dong groups, with OR (95% CI) of 1.07 (1.05-1.09), 1.07 (1.04-1.10), and 1.07 (1.04-1.11), respectively. However, this association was not significant in the Bouyei group (P=0.172). When GNRI was categorized, in the total population and Miao and Dong groups, higher GNRI quartiles(Q2-Q4) were associated with a gradient increase in MS risk compared with the Q1 reference group. However, this association was not statistically significant in the Q2 group or in any quartile group of the Bouyei ethnic group. Sensitivity analysis showed that the high-GNRI group had a significantly increased risk of MS (overall population: OR=1.98; Miao: OR=2.43; Dong: OR=1.76; all P<0.001), whereas the association remained non-significant in the Bouyei population (OR=1.03, P=0.845). Subgroup analysis showed that GNRI interacted with ethnicity and educational level, with stronger associations in the Dong group and among individuals with lower educational levels. RCS analysis indicated a linear positive association between GNRI and MS in the total population, while a non-linear positive association was observed in the Dong, Miao, and Bouyei groups.

Among the elderly Miao and Dong populations in Guizhou, an elevated GNRI was an independent risk factor for MS. No such association was observed in the Bouyei ethnic group. The relationship between GNRI and MS varied by ethnicity, indicating that ethnicity-specific nutritional intervention cut-offs and MS prevention strategies should be developed.