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

Background: Limited evidence, majorly based on questionnaire-derived measurements, was available to reflect long-term benefits of physical activity (PA) across different frailty levels.

Methods: We included 81,219 UK Biobank participants (mean age 61.88 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.

Results: Of the included participants, 54,081 (66.6 %) were robust and 1071 (1.3 %) were frail. Over a median follow-up of 10.68 years, 3825 (4.7 %) 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 0.57 (0.48-0.68), 0.39 (0.33-0.46), and 0.30 (0.25-0.36) for robust and 0.37 (0.23-0.58), 0.32 (0.20-0.53), and 0.18 (0.07-0.48) for frail people, respectively. MVPA-related associations were modified by frailty (P = 0.007). In joint analyses, compared with robust people with highest MVPA level, frail patients with MVPA <150 min/week had ~6 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.

Conclusion: 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.