Combined nutritional indices and DSST-defined cognitive performance in relation to all-cause mortality in older adults: A population-based analysis using NHANES 2011 to 2014 with mortality follow-up

Malnutrition and cognitive impairment are 2 common and interrelated conditions among older adults, each of which is linked to adverse health outcomes. Previous studies have usually examined these factors separately, and less is known about their combined association with mortality. This study examined whether the coexistence of nutritional risk (NR), defined using multiple nutritional indices, and digit symbol substitution test (DSST)-defined low cognitive performance was associated with all-cause mortality in older adults. Data were obtained from the National Health and Nutrition Examination Survey 2011 to 2014 with mortality follow-up through 2019. Nutritional status was evaluated using 3 validated indices that capture distinct dimensions of nutritional health: the Geriatric Nutritional Risk Index, Prognostic Nutritional Index, and Controlling Nutritional Status. Participants were classified as having high NR if any index indicated abnormal status. DSST-defined low cognitive performance was defined as a digit symbol substitution test score below the 25th percentile. Survey-weighted Cox regression models were applied to estimate hazard ratios and 95% confidence intervals for all-cause mortality after adjustment for demographic, socioeconomic, and clinical covariates. Among 1937 participants aged 60 years or older, 338 deaths occurred during a median follow-up of 6.6 years. In fully adjusted models, neither DSST-defined low cognitive performance nor high NR alone was significantly associated with mortality. Participants with both high NR and DSST-defined low cognitive performance had a higher mortality hazard (hazard ratio = 1.60; 95% confidence interval: 1.24-2.06; P = .032). Survival analysis revealed a gradual increase in mortality risk across the 4 combined exposure categories. The coexistence of high NR and DSST-defined low cognitive performance was associated with higher all-cause mortality among older adults and should be interpreted as a joint risk profile rather than evidence of synergy. These findings support the potential value of considering nutritional and cognitive information together in geriatric risk assessment.