Older adults typically have higher sedentary behaviour (SB) and lower physical activity (PA) than younger adults. Studies on replacing SB with PA in relation to all-cause mortality in racially diverse older adults remain limited.
This study included 122 966 older adults from the China Kadoorie Biobank (CKB) and 207 212 older adults from the UK Biobank (UKB). SB and PA were assessed using baseline questionnaires, with PA classified as light (LPA), moderate (MPA) or vigorous (VPA) based on metabolic equivalents. Cox proportional hazards models and isotemporal substitution models were used to examine the associations between replacing SB with different PA intensities and all-cause mortality.
Longer SB (per 30 min/day increase) was associated with a higher risk of all-cause mortality in both cohorts (CKB: HR 1.013, 95% CI 1.010 to 1.017; UKB: HR 1.012, 95% CI 1.009 to 1.015). PA of any intensity was associated with a reduced risk of all-cause mortality. In the CKB, replacing 30 min/day of SB with an equivalent duration of PA showed comparable protective associations (LPA: HR 0.963, 95% CI 0.958 to 0.968; MPA: HR 0.967, 95% CI 0.961 to 0.972; VPA: HR 0.965, 95% CI 0.960 to 0.971). In the UKB, replacing 30 min/day of SB with VPA was associated with the largest reduction in mortality risk (HR: 0.950, 95% CI 0.931 to 0.970).
Replacing SB with PA of any intensity was associated with reduced all-cause mortality risk in older adults, with variations across populations. These findings highlight the need for population-specific PA recommendations to promote healthy ageing.