Accelerometer-measured physical activity, frailty, and all-cause mortality and life expectancy among middle-aged and older adults: a UK Biobank longitudinal study

BackgroundPhysical activity (PA) is associated with reduced frailty and lower mortality rates among middle-aged and older adults. However, the extent to which total PA volume and specific PA intensities are associated with mortality risk across frailty status remains unclear. We aimed to investigate the interactive effects of accelerometer-measured PA with frailty on all-cause mortality and life expectancy.MethodsA total of 78,508 participants were sourced from the UK Biobank for analysis. Frailty index (FI) was used to assess frailty status. Physical activity and sedentary behavior were quantified through accelerometer measurements, capturing the total volume of physical activity (TVPA), moderate-to-vigorous-intensity physical activity (MVPA), light-intensity physical activity (LPA), and sedentary time (ST). Cox proportional hazard models were applied to calculate adjusted hazard ratios (HRs) and predict life expectancy.ResultsDuring a median follow-up of 6.9 years, 2618 deaths (2.9%) were identified. Compared with robust and physically active counterparts, individuals characterized by frailty, combined with the lowest levels of TVPA (HR 3.05, 95% CI: 2.50-3.71), MVPA (HR 2.65, 95% CI: 2.19-3.21), LPA (HR 2.26; 95% CI: 1.81-2.83), or the highest level of ST (HR 2.08, 95% CI: 1.66-2.61), were found to have the greatest risk of all-cause mortality after comprehensive adjustment. The dose-response relationship, assessed using restricted cubic splines, consistently demonstrated that regardless of frailty categories, higher levels of TVPA, MVPA, and LPA were associated with lower mortality risks, while higher ST level was associated with increased risk. Notably, across the frailty spectrum, individuals in the low tertile of TVPA, MVPA, and LPA, or the top tertile of ST, were associated with reduced life expectancy, with this pattern being more pronounced among frail men compared to frail women.ConclusionsOur findings highlighted the importance of increasing total PA volume, emphasizing MVPA and LPA, and reducing ST across the frailty spectrum to improve life expectancy.