Associations between body composition, physical capabilities and pulmonary function in healthy older adults

There are positive associations between pulmonary function (PF) and fat-free mass as well as muscle strength. Contrarily, negative associations were found with indirect measures of visceral adipose tissue (VAT). We aimed to differentiate between associations of body composition and PF by assessing mediating and moderating effects of physical capabilities.

Cross-sectional data were assessed among 40 healthy, free-living elderly (20 males) aged 65.1-81.2 years (mean±s.d. age: 72.2±4.3 years; body mass index: 25.6±3.7 kg/m²). Total and regional skeletal muscle (SM), and adipose tissue (AT) were measured using whole-body magnetic resonance imaging. Muscle strength by handgrip dynamometry, physical activity (PA) by questionnaire, and physical performance by gait speed and sit-to-stand test (STS). Forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV₁) were assessed by spirometry.

Positive associations between height-standardized FVC (FVCI) as well as FEV₁ (FEVI), and SM (r=0.435-0.520, P<0.05) were found; subcutaneous AT (SAT) and FVCI correlated negatively (r=-0.374; P<0.05). HGS and PA correlated positively with FEVI (r=0.456-0.608, P<0.05), HGS also with FVCI (r=0.595, P<0.05). Stepwise multiple regression using FVCI and FEVI as dependent variables, and total/thoracic SM, VAT, SAT, HGS, PA and physical performance as independent variables showed that (i) only HGS entered the regression for predicting FVCI (R²=0.351; standard error of estimation (SEE)=0.32 l), and (ii) HGS and PA explained 50% of FEVI (SEE=0.23 l). HGS mediated the relationship between SM and PF; the STS moderated the relationship between SM and FVCI.

In healthy elderly, PF is positively associated with SM; physical capabilities mediate and moderate these relationships.