The interplay of nutritional status and physical function on health outcomes in older adults: a longitudinal study in Singapore

BACKGROUND: Nutritional status and physical function are critical determinants of health and health-related quality of life (HRQoL) among older adults. However, their interplay and combined impact on multidimensional health outcomes remain underexplored. OBJECTIVES: This study investigated the longitudinal associations of nutritional status and physical function with physical, mental, and social health, HRQoL, and self-reported health (SRH) in older adults. METHODS: A total of 699 community-dwelling older adults (≥60 y) identified from the Population Health Index Survey were followed annually over 3 y. Nutritional status was assessed using the Mini Nutritional Assessment, and physical function was measured via the Late-Life Function and Disability Instrument. Mixed-effect models were employed to assess independent and interaction effects of nutritional status and physical function on health outcomes, including frailty, depression, loneliness, HRQoL, and SRH, adjusting for sociodemographic and lifestyle covariates. RESULTS: Undernutrition was associated with higher odds of frailty {odds ratio [95% confidence ratio (CI)]: 8.94 (4.48, 17.87)}, depression [14.94 (7.63, 29.23)], and loneliness [5.13 (2.77, 9.53)], lower HRQoL [β (95% CI): -0.10 (-0.13, -0.07)] and SRH [-8.27 (-10.81, -5.73)] compared with well-nourished individuals. Lower physical function was similarly associated with poorer health outcomes. Including both nutritional status and physical function in the model attenuated the associations for nutritional status. Although their interaction term was not associated with most health outcomes, a significant interaction was found for HRQoL, where the negative impact of undernutrition on EQ-5D scores was greater among those with impaired physical function [interaction term β (95% CI): -0.12 (-0.17,-0.07)]. CONCLUSIONS: Both nutritional status and physical function are independently and interactively associated with health outcomes in older adults. These findings underscore the need for integrated interventions targeting both nutritional status and physical function to promote healthy aging and reduce frailty. Future research should explore the mediating role of physical function and evaluate strategies to optimize health outcomes in older adults.