There are three mutually exclusive activities people can allocate time to across the 24 hours that days have; sleep, sedentary behaviour (SB) and physical activity (which can be also classified as light physical activity (LPA), moderate physical activity and moderate-to-vigorous physical activity (MVPA)). Although sleep, SB and physical activity are associated with cognitive performance and the risk of dementia, increasing or decreasing the time people spend on one of these behaviours requires taking away the time that they spend on the others, which has also an impact on health outcomes. Previous research has analysed lifestyle behaviours linearly. However, and despite the recognition that all behaviours influence cognitive performance, little is known about the optimal balance of time spent in each one of these (i.e. sleep, SB and MVPA) to maximise cognitive performance.
In a recent study published in the journal of Age and Ageing (Oxford University Press), a team of researchers led by Dr Audrey M. Collins from the AdventHealth Research Institute (Orlando, Florida, US) investigated how different uses of time impact brain health. The researchers recruited a group of 585 cognitively healthy adults aged 65 to 80 years old. Then, they examined the associations between time spent in sleep, SB, LPA, and MVPA across the 24-hour day, and cognitive performance. The team found that, on average per day, participants spent around 7.5 hours sleeping, 12.0 hours in SB, 4.0 hours in LPA, and 0.5 hours in MVPA. Higher levels of MVPA (i.e. physical activity that is performed at higher intensities and increases the heart rate and breathing) were related to better cognitive performance. Specifically, MVPA improved how fast the brain thinks, how well we plan and focus and the ability someone has to store information for a short time. This was true regardless of whether time was taken away from sleep, SB or LPA.
The opposite was also true, that is, lower levels of MVPA were associated with worse cognitive performance. However, these findings did not extend to episodic memory or to visuospatial function outcomes (i.e. the what, when and where of an event and the ability to navigate through spaces and recognise places, respectively). Although the results of this study need to be tested longitudinally and experimentally to inform future dementia prevention guidelines, they showed that how people choose to spend their time during the 24-hour day matters and is related to our brain health. Prioritising moderate-to-vigorous physical activity in late adulthood is key and may be beneficial for cognitive performance.
https://academic.oup.com/ageing/article/54/4/afaf072/8106300