Frailty and frailty progression in relation to the risk of benign prostatic hyperplasia/lower urinary tract symptoms among Chinese middle-aged and older men: a prospective cohort study

Background Frailty and benign prostatic hyperplasia/lower urinary tract symptoms (BPH/LUTS) are age-related conditions, but their longitudinal relationship remains unclear. This study investigated associations between frailty index (FI) trajectories, baseline frailty status, and incident BPH/LUTS in Chinese middle-aged and older men.Methods Data from three waves (2011–2015) of the China Health and Retirement Longitudinal Study (CHARLS) were analyzed. Group-based trajectory modeling identified FI trajectories. Multivariable logistic regression examined associations of baseline frailty status (robust, prefrail, frail) and FI trajectories with incident BPH/LUTS. Incremental predictive value of trajectories beyond baseline status was quantified using net reclassification improvement (NRI) and integrated discrimination improvement (IDI).Results Among 4,449 men, four distinct FI trajectories were identified. Compared to the Persistently Low trajectory, Moderately Increasing and High-Increasing trajectories showed significantly higher BPH/LUTS risk (ORs: 2.01 [1.38–2.99] and 2.82 [1.79–4.45]; p-trend < 0.001). Baseline prefrail and frail status were also associated with elevated risk (ORs: 1.47 [1.13–1.90] and 1.67 [1.10–2.49], respectively). Dynamic frailty trajectories demonstrated improved risk reclassification over baseline assessment alone (continuous NRI: 0.284, p < 0.001; IDI: 0.011, p = 0.001).Conclusions Both baseline frailty status and dynamic FI trajectories were independently associated with BPH/LUTS risk. Longitudinal trajectories exhibited stronger associations and greater predictive value, highlighting the importance of monitoring frailty progression for improved risk stratification and targeted prevention.