Frailty and its Association With Strength and Balance Variables in Chilean Older Adults: A Structural Equation Model

BACKGROUND: Frailty is a geriatric syndrome associated with adverse health outcomes in older adults. However, the specific contribution of neuromuscular factors-including inspiratory strength, lower-limb strength, and balance-to frailty development remains unclear. PURPOSE: This study aimed to investigate the associations of inspiratory strength, lower-limb strength, and static and dynamic balance with frailty in Chilean older adults. METHODS: A cross-sectional observational study was conducted in 209 older adults. Frailty was assessed using Fried's phenotype. Inspiratory strength (maximum inspiratory pressure), lower-limb strength (quadriceps peak force and Five Times Sit-to-Stand Test), static balance (posturography), and dynamic balance (Limits of Stability and Timed Up and Go Test) were evaluated. A structural equation model was used to predict a latent frailty variable from age, gender, strength, and balance. RESULTS: The final structural equation model showed excellent fit (χ2(1) = 3.30, P > .05; comparative fit index = 0.995; root mean square error of approximation = 0.106; Standardized Root Mean Squared Residual [SRMR] = 0.048). Specifically, values of more than 0.95 for the comparative fit index and less than 0.08 for the SRMR are indicative of excellent fit. Inspiratory strength (β = -0.374, P < .01), quadriceps peak force (β = -0.463, P < .01), and dynamic balance (β = 0.439, P < .01) significantly predicted frailty, explaining 79.4% of its variance. Static balance was not a significant predictor. CONCLUSIONS: Neuromuscular factors, particularly inspiratory strength, quadriceps strength, and dynamic balance, are key factors associated with frailty. Future research should investigate whether interventions focused on inspiratory muscle training, lower-limb strengthening, and functional balance exercises are able to prevent or reduce frailty in older adults.