Objective To investigate the relationship between the geriatric nutritional risk index (GNRI) and cognitive function among the rural residents aged 60 and above in a county of Guangxi, and further analyze the mediating role of high-density lipoprotein cholesterol (HDL-C) in this association.

Methods This study utilized data from the baseline cross-sectional survey of the Guangxi Environment and Health Middle-aged and Elderly Cohort, with a final inclusion of 1, 652 participants. The cognitive status of the participants was assessed using the mini-mental state examination (MMSE) questionnaire, and they were categorized into the cognitive impairment group and normal cognitive function group based on their MMSE scores and educational attainment. Multivariable logistic regression analyses were performed to evaluate the association between the GNRI and cognitive function. A restricted cubic spline (RCS) model was constructed to analyze their nonlinear relationship. A mediation model was subsequently conducted to investigate the intermediary role of HDL-C in this association.

Results In this study, among the participants, 325 (19.67%) exhibited cognitive impairment. After adjusting for covariates, compared with the lowest quartile of GNRI, the highest quartile of GNRI was significantly negatively correlated with the risk of cognitive impairment (OR=0.557, 95% CI: 0.382-0.813, P < 0.05). When the GNRI exceeded 101.94, the risk of cognitive impairment in the elderly population showed a decreasing trend, and this trend was more pronounced in the female population. However, the mediation effect of HDL-C in the association between GNRI and cognitive function was not statistically significant.

Conclusion Higher GNRI levels are associated with a reduced risk of cognitive impairment, but HDL-C does not mediate this association.