Associations of physical activity bout duration and fragmentation with future dementia, depression, and anxiety: a multi-modal UK Biobank study.

It's unclear whether prolonged physical activity confers greater benefits on future dementia, depression, and anxiety risk than sporadic activity. Among 66,483 UK Biobank participants, we found that prolonged daily bouts of moderate-to-vigorous physical activity (MVPA) and lower activity fragmentation were associated with a significantly lower risk of future dementia, depression, and anxiety, independent of total physical activity. Compared with never engaging in MVPA, the lowest observed risk of dementia, depression, and anxiety occurred for bouts lasting 13 min (72% lower), 36 min (52% lower), and 36 min (50% lower), respectively. Compared with the highest observed activity fragmentation, the lowest observed fragmentation was associated with an 82, 57, and 52% lower risk of dementia, depression, and anxiety, respectively. Prolonged MVPA and lower fragmentation were associated with greater left hippocampal volume and lower white matter hyperintensity volume. Our study suggests that prolonged physical activity should be encouraged to reduce the risk of dementia, depression, and anxiety.