221Association of physical activity bout length and changing intensity with mortality in UK Biobank

Abstract

Abstract Background Spending more time active (and less time sedentary) is associated with many health benefits but it is unclear whether these associations differ depending on whether time spent sedentary or in moderate-vigorous physical activity (MVPA) is accumulated in long or short bouts. We used a novel analytical approach to examine whether length of sedentary and MVPA bouts associates with all-cause mortality. Methods We used data on 79,507 participants from UK Biobank. We derived the total time participants spent in activity categories (sleep, sedentary, light activity and MVPA) and in sedentary and MVPA bouts of short (1-15 minutes), medium (16-40 minutes) and long (41+ minutes) duration, on average per day. We used Cox proportion hazards regression to estimate the association of spending 10 minutes more average daily time in one activity or bout length category, coupled with spending 10 minutes less time in another, with all-cause mortality. Results Those spending more time in MVPA had lower mortality risk, irrespective of whether this replaced time spent sleeping, sedentary or in light activity. We found little evidence to suggest that mortality risk differed depending on the length of sedentary or MVPA bouts. Conclusions We uniquely show that higher total MVPA improves health irrespective of whether it is obtained from several short bouts or fewer longer bouts, supporting recent policy changes in some countries. Key messages Our results suggest that time spent in MVPA associates with lower mortality risk irrespective of whether it is obtained from several short bouts or fewer longer bouts.