# The association between skeletal muscle mass and functional capacity outcomes in Chinese older adults: a national community-based study

## TL;DR

This study finds that muscle mass in older adults is linked to better daily functioning, with specific thresholds and differences between men and women.

## Contribution

The study identifies sex-specific thresholds of skeletal muscle mass that influence functional capacity in older adults.

## Key findings

- Higher appendicular skeletal muscle mass index is inversely associated with lower BADL and IADL scores.
- Thresholds of 6.2 kg/m² for men and 5.2 kg/m² for women mark significant changes in functional capacity associations.
- Stronger associations were observed in men, urban residents, and those with stroke or cardiovascular disease.

## Abstract

Maintaining functional independence in older adults is a critical public health objective. Although skeletal muscle mass is recognized as a key contributor to functional capacity outcomes, the exact relationship between them among community-dwelling older adults requires further investigation.

This cross-sectional study analyzed data from 13,322 participants aged ≥65 years from the 2018 Chinese Longitudinal Healthy Longevity Survey (CLHLS). Appendicular skeletal muscle mass index (ASMI) was calculated using a validated anthropometric equation, while functional capacity outcomes were assessed using basic and instrumental activities of daily living (BADL/IADL) scores. Multivariable linear regression, generalized additive models, and threshold effect analysis were employed to evaluate associations, with adjustments for demographic, socioeconomic, lifestyle, and comorbidity factors.

In fully adjusted models, ASMI showed significant inverse associations with both BADL score (β = −0.072, 95% CI: −0.103 to −0.042) and IADL score (β = −0.225, 95% CI: −0.290 to −0.159). Threshold effect analysis revealed sex-specific inflection points: below 6.2 kg/m2 in men and 5.2 kg/m2 below in women, ASMI was negatively associated with BADL/IADL scores, whereas above these thresholds, the associations weakened or reversed. Subgroup analyses indicated stronger effects among men, urban residents, and those with stroke or cardiovascular disease.

Muscle mass demonstrates sex-specific, non-linear associations with functional capacity outcomes in older adults, identifying critical thresholds that may inform targeted strategies to preserve independence.