Metabolic phenotypes and pulmonary function in aging: the mediating roles of cognitive function and depression in CHARLS.

BACKGROUND: Metabolic phenotypes, defined by weight status and metabolic health, influence various physiological outcomes, yet their impact on pulmonary function in aging populations remains unclear. This study examines the longitudinal association between metabolic phenotypes and peak expiratory flow (PEF), considering the mediating roles of cognitive function and depression. METHODS: We analyzed longitudinal data (2011-2015) from 4,393 participants (mean age 58.9 years; 56.7% female) in the China Health and Retirement Longitudinal Study (CHARLS). Participants were categorized into four metabolic phenotypes: metabolically healthy normal weight (MHNW), metabolically healthy overweight/obese (MHO), metabolically unhealthy normal weight (MUNW), and metabolically unhealthy overweight/obese (MUO). PEF was assessed via linear mixed model, adjusting for sociodemographic and lifestyle factors. Chain mediation analyses evaluated cognitive function (composite score) and depression (CES-D scale), with sensitivity analyses verifying robustness. RESULTS: Among middle-aged and older women, MHO was associated with modestly higher PEF versus MHNW (middle-aged: β = 7.410, P < 0.001; older: β = 10.358, P = 0.038), and MUO with higher PEF in older women (β = 14.990, P < 0.001). No significant associations were found in men. Chain mediation showed metabolic phenotypes indirectly influenced PEF via cognition→depression (total indirect effect: 0.008, P = 0.001; 17% of total effect). Sensitivity analyses confirmed robustness, though interpretations are cautious given PEF's limitations as a proxy for full lung function. CONCLUSIONS: Metabolic phenotypes significantly may influence pulmonary function in aging populations, partially mediated by cognitive and mental health, with distinct sex- and age-specific patterns. However, higher PEF in overweight/obese groups warrants caution, potentially reflecting mechanical effects rather than overall respiratory benefit. Integrated metabolic and neuropsychological health management may improve respiratory outcomes in older adults.