Probable respiratory sarcopenia trajectories and the risk of incident chronic diseases: findings from the China health and retirement longitudinal study

BACKGROUND: With the acceleration of population aging, the coexistence of multiple chronic diseases has become a major public health concern among older adults. Respiratory sarcopenia (RS) reflects dual impairments in systemic and respiratory muscle function; however, longitudinal evidence regarding its association with multisystem chronic diseases remains limited. This study aimed to systematically evaluate the prospective associations between longitudinal trajectories of an epidemiologic surrogate phenotype for probable respiratory sarcopenia (probable RS) and the risk of multiple incident chronic diseases. METHODS: This study was based on the China Health and Retirement Longitudinal Study cohort and included 4,784 middle-aged and older participants with follow-up data. Probable RS was defined using peak expiratory flow rate (PEFR) and appendicular skeletal muscle mass (ASM). Group-based trajectory modeling (GBTM) was used to identify joint longitudinal trajectories of PEFR and ASM. Multivariable Cox proportional hazards regression models were subsequently applied to evaluate the associations between these trajectories and incident chronic diseases. The Benjamini-Hochberg false discovery rate (FDR) method was used for multiple-comparison correction. RESULTS: The GBTM identified three stable longitudinal trajectory groups: the dual high/normal trajectory group (29.8%), the single impaired trajectory group (47.6%), and the dual low trajectory group (22.6%). After multivariable Cox regression analysis with FDR correction, compared with the dual high/normal trajectory group, participants in the dual low trajectory group with persistently low PEFR and low ASM had significantly increased risks of incident arthritis (HR = 1.95, 95% CI: 1.54-2.47), asthma (HR = 4.31, 95% CI: 2.11-8.81), chronic lung disease (HR = 2.27, 95% CI: 1.63-3.17), and hypertension (HR = 1.56, 95% CI: 1.21-2.00) during follow-up (all FDR-P < 0.05). Sensitivity analyses further confirmed a significant synergistic amplification effect of concurrent low PEFR and low ASM on disease risk. CONCLUSIONS: Dual longitudinal declines in skeletal muscle and respiratory function were prospectively associated with increased risks of specific chronic diseases among middle-aged and older adults. These trajectories of this surrogate phenotype may serve as potential phenotypic markers for multimorbidity risk stratification. Future community-based prospective intervention trials may be warranted to determine whether targeted improvements in respiratory and skeletal muscle function can effectively prevent chronic diseases.