Skeletal and cardiac muscle longitudinal associations in the Baltimore Longitudinal Study of Aging (BLSA).

Abstract

Sarcopenia, the age-related loss of skeletal muscle mass and function, has been linked to adverse health outcomes. Cross-sectional associations have been observed between skeletal and cardiac muscle mass and function in healthy, community-dwelling older adults during normative aging. Further longitudinal studies on the skeletal muscle-cardiac axis during aging are needed to inform the temporal patterns and impact of these associations. We analyzed data from participants from the Baltimore Longitudinal Study of Aging. Individual longitudinal rates of change (random slopes) of echocardiography-derived cardiac function, appendicular lean mass (ALM), and maximal handgrip strength (HGS) were estimated with linear mixed-effects models. The associations between baseline measurements and rates of change (_Change) were examined using Pearson correlation and multiple linear regression. Continuous variables are expressed as mean ± standard deviation (SD). Among 1025 participants (66.6 ± 13.1 years, 47.8% male), the baseline mean HGS was 33.1 ± 11.0 kg, and ALM was 20.8 ± 5.3 kg; the mean left ventricular ejection fraction was 67.5 ± 9.7%, and LV mass (LVM) was 145.6 ± 50.4 g. With aging, HGS decreased by 0.36 kg/year (95% CI: -0.41, -0.31), ALM decreased by 25.1 g/year (95% CI: -34.7, -15.5), and LVM decreased by 0.730 g/year (95% CI: -0.998, -0.460). Both ALM_Change and HGS_Change were inversely correlated with advancing age ([r = -0.159 p < 0.001] and [r = -0.172 p < 0.001], respectively), while LVM_Change was not (p = 0.178). Adjusting for baseline, ALM_Change was significantly associated with LVM_Change independently of age, sex, and LVM (β = 0.287, p < 0.001, adj. R² = 0.663); the association persisted after adjustment for pulse pressure, mean arterial pressure, and body mass index. The interaction term sex*baseline-adjusted ALM_Change was statistically significant (p < 0.050). ALM_Change was also correlated with LVEF_Change (r = 0.102, p = 0.001), while HGS_Change was not significantly correlated with LVM_Change (p = 0.642). Among community-dwelling normative aging adults, age-associated decline in skeletal muscle mass correlated with reductions in LVM and function, independently of age, sex, and hemodynamic loading conditions. Our findings suggest a skeletal muscle-cardiac axis characterized by parallel declines beginning in early aging, preceding cardiovascular disease. Further studies exploring cardiac and skeletal muscle aging-related declines may direct interventions to halt these adverse processes concurrently.