Frailty Increases the Risk and Frequency of Lower Respiratory Tract Infections in Older Adults: A Multicenter Prospective Cohort Study

Background: Lower respiratory tract infections (LRTIs) are a leading cause of morbidity in older adults, yet risk stratification based solely on chronological age remains insufficient. Frailty, reflecting cumulative declines in physiological reserve, may better capture susceptibility to respiratory infections. We aimed to investigate the association of frailty with the risk and frequency of LRTIs in older adults. Methods: We conducted a multicenter prospective cohort study among older adults in senior living communities in China, from November 2023 to September 2025. Baseline frailty was evaluated using the clinical frailty scale. Participants were monitored for LRTIs throughout the follow-up period. The association between frailty and LRTI risk was evaluated using cause-specific Cox proportional hazards models, with subgroup and sensitivity analyses performed to assess the consistency and robustness of the findings. For the LRTI frequency analysis, Poisson generalized estimating equation models were applied. Results: The cohort included 522 older adults with a median follow-up of 473.5 days. 104 LRTI episodes were documented, and 13.4% participants experienced at least one event. Frailty was a significant predictor of LRTI risk (adjusted HR, 1.29; 95% CI, 1.10-1.52), which remained robust across different LRTI types and sensitivity analyses. This association was particularly pronounced in participants with albumin levels < 45 g/L. Beyond initial infection risk, frailty was also associated with an increased frequency of LRTIs (adjusted incidence rate ratio, 1.30; 95% CI, 1.09-1.54). Conclusions: Frailty constitutes an independent and modifiable risk factor for LRTIs in older adults, emphasizing the importance of frailty management in LRTI preventive strategies.