Association of physical frailty with cardiac conduction disorder events in the UK Biobank

Background Practical markers for identifying individuals at risk of cardiac conduction disorders (CCDs) before overt disease are limited. Physical frailty reflects reduced physiological reserve and may capture vulnerability beyond chronological age and individual cardiometabolic factors. Herein, we investigated the association of physical frailty with incident CCD in the UK Biobank cohort. Methods We included 423,162 participants with data for a modified Fried frailty phenotype and linked health-record follow-up after excluding those with cardiovascular disease, CCDs, or pacemaker implantation at baseline. Participants were classified as non-frail, prefrail, or frail. The primary outcome was incident CCD, and the secondary outcomes were severe conduction block and left bundle branch or fascicular block. Cox proportional hazards models estimated hazard ratios (HRs) and 95% confidence intervals (CIs). Results Overall, 58.2% of participants were non-frail, 38.5% were prefrail, and 3.3% were frail; 18,067 incident CCD events occurred during the follow-up. Compared with participants who were non-frail, participants who were prefrail and frail were at higher risks of CCDs after multivariable adjustment [HR, 1.23 (95% CI, 1.19–1.27) and HR, 1.71 (95% CI, 1.60–1.83), respectively; P for trend <0.01]. The corresponding HRs were 1.13 (95% CI, 1.09–1.18) and 1.44 (95% CI, 1.32–1.59) for severe conduction block and were 1.24 (95% CI, 1.17–1.32) and 1.61 (95% CI, 1.43–1.81) for left bundle branch or fascicular block. Conclusions Physical frailty was associated with graded increases in incident CCD and related conduction outcomes, with excess risk evident at the prefrailty stage. Frailty assessment may help identify individuals with increased susceptibility, although the observational design does not establish causality or demonstrate that modifying frailty would reduce risk.