Sarcopenia predicts dynamic lung function trajectories in middle-aged and older adults: A national cohort study

Sarcopenia, defined by progressive loss of skeletal muscle mass and strength, may be related to reduced expiratory performance in later life. However, evidence linking relative muscle strength (RMS) to peak expiratory flow (PEF) and PEF-based respiratory performance in Asian populations remains limited. This study examined cross-sectional and longitudinal associations between RMS and PEF-based outcomes and explored nonlinear and subgroup variations.

Data were obtained from the China Health and Retirement Longitudinal Study (CHARLS). RMS was computed as maximal handgrip strength divided by appendicular skeletal muscle mass (ASM). The primary respiratory measures were peak expiratory flow (PEF), PEF% predicted, low PEF% predicted (<80%), and severe low PEF% predicted (<60%). PEF% predicted was calculated using sex-, age-, and height-specific adult reference equations from Zhong. Multivariable regression models examined associations between RMS and PEF-based outcomes; longitudinal models estimated four-year changes and incident low/severe low PEF% predicted.

Each one standard deviation (1-SD) higher RMS was associated with higher PEF% predicted (β = 2.92, 95% CI 2.31-3.53) and higher absolute PEF (β = 10.29, 95% CI 7.92-12.66). Nonlinear analyses suggested that the association plateaued at RMS values around 1.8-2.0. Longitudinally, the third RMS quartile showed the strongest association with slower PEF decline (β = 3.12 units/year less decline vs Q1). Associations were generally more evident in males and smokers, with endpoint-specific subgroup differences for diabetes or stroke. Higher RMS was also correlated with lower CRP and more favorable metabolic profiles, suggesting possible inflammatory and metabolic pathways.

Higher RMS was associated with better PEF-based expiratory performance and lower odds of low PEF% predicted in middle-aged and older adults. These findings support RMS as a simple functional marker related to PEF performance during aging, while recognizing that PEF does not replace spirometry-based assessment of obstructive or restrictive lung disease.