Dose-response associations of accelerometer-measured physical activity with mortality across frailty levels: A prospective cohort study

Limited evidence, majorly based on questionnaire-derived measurements, was available to reflect long-term benefits of physical activity (PA) across different frailty levels. We included 81,211 UK Biobank participants (mean age 61.87 years; 41.2 % men) with accelerometer data. Participants were categorized using frailty phenotype as robust, prefrail, and frail. Restricted cubic splines described the associations of continuous light intensity PA (LPA), moderate/vigorous intensity PA (MVPA), and total PA (TPA) levels with all-cause mortality. Adjusted hazard ratios (HRs) of outcomes by multi-categorical LPA and MVPA levels were estimated. Further joint analyses were performed if significant interaction existed between PAs and frailty. Of the included participants, 54,094 (66.6 %) were robust and 1070 (1.3 %) were frail. Over a median follow-up of 7.37 years, 2221 (2.7 %) deaths occurred. For all-cause mortality, L-shaped nonlinear associations existed for LPA, MVPA, and TPA. Compared with <150 min/week, MVPA of 150-300, 300-600, and ≥600 min/week-related HRs were 0.60 (0.48-0.75), 0.42 (0.34-0.52), and 0.33 (0.26-0.42) for robust and 0.29 (0.16-0.51), 0.25 (0.13-0.48), and 0.12 (0.03-0.52) for frail people, respectively. MVPA-related associations were modified by frailty (Pinteraction = 0.007). In joint analyses, compared with robust people with highest MVPA level, frail patients with MVPA <150 min/week had ~7 times higher risk of mortality, while those with frailty but MVPA ≥150 min/week had a relatively lower mortality risk than robust people with MVPA <150 min/week. Dose-response associations existed between device-measured PA levels and mortality risk across different frailty levels. Frail patients benefited greater via MVPA engagement, which partially attenuated frailty-related excessive risk.