Identification and comparison of the predictors of maximal inspiratory force and handgrip in a healthy elderly population. The proof study

Background: A severe weakness of peripheral muscles occurs in half of the persons aged 80 years or older. The common factors between muscle depletion and reduced respiratory strength have not yet been established.

Objective: In the subjects of the Proof cohort, we aimed to identify, among body composition, pulmonary function and energy expenditure parameters, the predictors of maximal inspiratory pressure (MIP) as an index of respiratory muscle strength and handgrip (HG) as an index of peripheral muscle strength.

Subjects and methods: In 375 healthy elderly subjects aged 72 ± 1 years, fat mass (FM) and fat free mass (FFM) were assessed by DEXA, the last being also indexed to height (FFMI). Spirometry was performed and daily energy expenditure (DEE) was estimated by a questionnaire. After three years, MIP and HG of the dominant arm were determined and the predicting value of pulmonary function tests, body composition and DEE on these parameters was tested.

Results: Mean MIP and HG were 77 ± 26% and 106 ± 19% of the predicted value (%pred) with 90 (24%) and 30 (8%) subjects below standards, respectively. There was a significant but weak correlation between MIP%pred and HG%pred (r = 0.175, p < 0.001). Logistic regression showed that low MIP was predicted by trunk FFM and FFMI in women, and DEE in men. Low HG was predicted by trunk FM in men only.

Conclusions: The predictors of a reduction of MIP in the elderly differ from those of HG, suggesting a differential regulation of respiratory muscle and arm strength.