Lung function and frailty: Dose–response relationship, mediation effects, and prediction model

Lung function, cognitive ability, and lifestyle are key factors affecting the health of older adults, especially in predicting frailty. However, the relationship between lung function and frailty is unclear, particularly in Chinese middle-aged and elderly populations, and clinical frailty assessment methods lack standardization. This study aimed to develop a frailty risk prediction model by analyzing lung function, cognitive ability, and lifestyle factors, providing a basis for early frailty screening and intervention. Data from the baseline wave (2011-2012) of the China Health and Retirement Longitudinal Study were used, including 6065 individuals aged ≥ 45 years. Peak expiratory flow (PEF) was measured using standardized procedures. The percentage of predicted PEF (PEFpred%) was calculated as (measured PEF/predicted PEF) × 100%, where predicted values were estimated based on age-, sex-, and height-adjusted reference equations derived from a Chinese population. Frailty was assessed through a questionnaire, and relevant covariates were recorded. Multilevel logistic regression analyzed the relationship between PEFpred% and frailty, with Bootstrap methods evaluating the mediating role of cognitive function. Least absolute shrinkage and selection operator regression and cross-validation were used to identify key predictors for the frailty risk model, evaluated by receiver operating characteristic and calibration curves. The mean age of the participants was 58.3 years, with 51% female. Twenty-three point five percent had a PEFpred% <60%. Higher PEFpred% was associated with lower frailty risk. Dose-response analysis showed a nonlinear relationship, with significant risk increases when PEFpred% was < 80.03%. Cognitive function partially mediated the relationship, explaining 20.11% of the effect. The model based on PEFpred%, cognitive function, and other variables showed good performance: area under the curve was 0.796 in the training set and 0.775 in the validation set. PEFpred% is a useful predictor of frailty risk in Chinese middle-aged and elderly individuals, with cognitive function playing a key mediating role. The frailty risk prediction model demonstrates good performance and warrants further clinical validation.