Respiratory muscle strength for discriminating frailty in community-dwelling elderly: a cross-sectional study

To compare obtained and predicted inspiratory and expiratory muscle strength between frail, pre-frail, and non-frail older people; to examine the association between inspiratory and expiratory muscle strength and frailty in older people; and to determine cut-off points for inspiratory and expiratory muscle strength for discriminating frailty in older people.

A cross-sectional study was conducted with 379 community-dwelling older adults. Frailty was assessed using Fried's phenotype, while inspiratory and expiratory muscle strength were measured with maximum inspiratory and maximum expiratory pressures. Inferential analyses were performed using paired Student t-tests, one-way analysis of variance (ANOVA) tests, and a multinomial logistic regression model. ROC curves were constructed to establish cut-off points of maximum inspiratory and expiratory pressures for discriminating frailty and pre-frailty.

Frail and pre-frail participants presented significantly lower mean inspiratory and expiratory pressures compared to non-frail participants; values were significantly lower than predicted. Inspiratory and expiratory muscle strength were inversely associated with frailty and pre-frailty. Cut-off points ≥-50cmH₂O and ≤60cmH₂O for maximum inspiratory and expiratory pressures, respectively, were established as optimal discriminators of frailty. The cut-off point ≤65cmH₂O for maximum expiratory pressure was established as a discriminant for the presence of pre-frailty.

Inspiratory and expiratory muscle strength were lower in frail than in pre-frail older adults, and lower in pre-frail than in non-frail peers. Frailty and pre-frailty were inversely associated with inspiratory and expiratory muscle strength. Cut-off points for inspiratory and expiratory muscle strength may be useful in clinical practice for discriminating frailty and pre-frailty in older adults.