Peak Expiratory Flow and Its Trajectories Associated With Frailty in Older Adults: A Prospective Cohort Study.

BACKGROUND: Current evidence indicates an association between peak expiratory flow (PEF) and frailty in older adults, yet critical gaps persist regarding: the longitudinal dynamics of PEF trajectories, their temporal relationships with frailty progression and underlying biological mechanisms. This study aimed to investigate the associations of baseline PEF and its longitudinal trajectories with incident frailty risk, while elucidating potential mechanistic pathways in older adults. METHODS: A prospective cohort study was conducted of general community-dwelling adults aged ≥ 65 years from 2006 to 2022 in the Health and Retirement Study from the United States. PEF trajectories were identified using group-based trajectory modelling. Frailty was assessed by the Fried frailty phenotype, encompassing five key components: weight loss, exhaustion, physical activity, gait speed and grip strength. Participants were classified as frailty if they met three or more. Cox proportional hazard models were applied to estimate the associations. RESULTS: A total of 5686 participants with a median age of 72.5 (interquartile range: 68-77) years and 3262 (57.37%) females were included and followed up for 34 052 person-years with an incidence density of frailty of 31.69 per 1000 person-years. The proportion of White, Black and other ethnic populations was 83.45%, 12.56% and 3.99%, respectively. Compared with participants in the Q5 level of PEF at baseline, its Q4, Q3, Q2 and Q1 levels increased the risk of frailty by 38% (hazard ratio [HR] = 1.38, 95% confidence interval [CI]: 1.09-1.74), 86% (HR = 1.86, 95% CI: 1.46-2.38), 112% (HR = 2.12, 95% CI: 1.46-2.38) and 172% (HR = 2.72, 95% CI: 2.11-3.51), respectively. Similar associations were observed when using standardized residuals of PEF. A total of 1826 participants were included to model PEF trajectories over an 8-year period, identifying five trajectories: high level (6.63%), upper-moderate level (14.84%), moderate level (24.15%), lower-moderate level (41.29%) and low level (13.09%). Compared with the high level, the low level increased the risk of frailty by 522% (HR = 6.22, 95% CI: 2.53-15.26). Low PEF over both short and extended periods was associated with an increased risk of various degrees of frailty phenotypes. CONCLUSIONS: Low PEF over both short and extended periods was significantly associated with an increased risk of frailty in older adults. These findings highlight the importance of monitoring pulmonary function as a potential marker for frailty risk and suggest that PEF may influence different frailty phenotypes to varying extents.