Exploring the complex associations among risks of malnutrition, sarcopenia, and frailty in community-dwelling older adults

BackgroundMalnutrition, sarcopenia, and frailty are age-related conditions that are associated with multiple health-related negative outcomes. However, the complex associations between them remain to be elucidated. The aims of the study were to explore: (1) whether the risk of sarcopenia has a mediator effect on the association between risks of malnutrition and frailty; and (2) whether physical activity (PA) level modulates this mediator effect in community-dwelling older adults. MethodsThis cross-sectional study involved 593 older adults (62.73% female; mean age = 71.35 +/- 5.86 years). The Mini Nutritional Assessment-Short Form (MNA-SF), the SARC-F Questionnaire, and the FRAIL Questionnaire were used to assess the risks of malnutrition, sarcopenia, and frailty, respectively. The International Physical Activity Questionnaire Short Form (IPAQ-SF) was employed to assess PA level. Using the Hayes PROCESS macro (Models 4 and 7), mediation and moderated mediation analyses were performed. ResultsThe mediation analysis demonstrated that the MNA-SF had a significant effect on the SARC-F (B=-0.325; p < 0.001) and the SARC-F, in turn, had a significant effect on the FRAIL (B = 0.341; p < 0.001). The total (B=-0.171; p < 0.001), direct (B=-0.061; p = 0.001), and indirect (B=-0.111; bootstrap CI did not include zero, which indicates a significant effect) effects of MNA-SF on FRAIL were significant, showing that 65% of the association between the MNA-SF and FRAIL was explained by the SARC-F acting as a mediator. The moderated mediation analysis demonstrated that the association between MNA and SARC-F was moderated by the PA level (B = 0.253; p = 0.016). The SARC-F mediated and relatively enhanced the association between MNA-SF and FRAIL only in older adults with a moderate PA level (B=-0.120; CI: -0.154 to -0.085). ConclusionsThe SARC-F partially mediates the association between the MNA-SF and the FRAIL, indicating that malnutrition affects frailty through an indirect path via sarcopenia. Furthermore, the PA level moderates this mediator effect, with sarcopenia serving as a mediator in older adults with moderate a PA level but not in those with a low PA level. These findings reveal that it may be beneficial to consider PA level in combination with malnutrition and sarcopenia in the management and prevention of frailty in community-dwelling older adults.