Baseline peak expiratory flow and incident hip fracture in older Chinese adults: A prospective CHARLS cohort study

Peak expiratory flow (PEF), a simple measure of respiratory function, may be linked to skeletal health through shared pathways related to physiological reserve and functional capacity. However, the long-term association between PEF and incident hip fracture in community-dwelling older adults remains unclear. We conducted a longitudinal analysis of participants aged ≥60 years from the China Health and Retirement Longitudinal Study, using 2013 as baseline and follow-up waves in 2015, 2018, and 2020 (up to ~7 years). Baseline PEF was defined as the maximum of 3 attempts, and incident hip fracture was identified as self-reported hip fracture first reported during follow-up. Associations were evaluated using Cox proportional hazards models stratified by self-rated health, with multiple imputation for missing covariates. PEF was modeled per 1-standard deviation increase and by quartiles. A prespecified conceptual framework distinguished likely confounders from potentially pathway-related variables. Supplementary discrimination analyses used C-index and time-dependent area under the receiver operating characteristic curve. Among 5789 participants, incident hip fractures occurred in 98 (6.5%), 76 (5.1%), 51 (3.7%), and 46 (3.2%) individuals from the lowest to highest PEF quartile (P < .001). Per 1-standard deviation higher PEF, hazard ratios were 0.70 (95% CI: 0.62-0.80) in the crude model, 0.79 (0.68-0.91) in the primary confounder-adjusted model, and 0.87 (0.74-1.02) in the broader model. For quartiles, Q4 versus Q1 hazard ratios were 0.46 (0.32-0.65), 0.63 (0.43-0.93), and 0.80 (0.53-1.20), respectively. Restricted cubic splines showed no evidence of nonlinearity (P = .866). Supplementary discrimination analyses showed higher C-index and time-dependent area under the receiver operating characteristic curves for the broader model than for the unadjusted and primary confounder-adjusted models. Higher baseline PEF was associated with lower incident hip fracture risk in crude and partially adjusted analyses, but the association was attenuated after broader adjustment. Baseline PEF appears to have limited stand-alone prognostic value and may be better viewed as a pragmatic signal prompting broader geriatric assessment rather than as a stand-alone fracture risk tool.