Undertaking between six to seven minutes of moderate or vigorous physical activity (MVPA) every day could improve cognitive performance, finds a new study led by UCL researchers.
The research, published in the Journal of Epidemiology & Community Health, found that more intense exercise is better for working memory and mental processes, such as planning and organisation. Meanwhile, being sedentary or doing light intensity activity is associated with poorer brain power.
For the study, researchers examined 4481 participants between the ages of 46-47, from the 1970 British Cohort Study, comprising of people born across England, Scotland, and Wales in 1970 whose health was tracked throughout childhood and adulthood.
Participants were asked to fill in detailed health, background, and lifestyle questionnaires, and to wear an activity tracker for up to 7 days and for 10 consecutive hours a day.
They also took various cognitive tests for verbal memory (immediate and delayed word recall tasks) and executive function (verbal fluency and processing speed/accuracy).
Scores for each test were then totalled up to produce an overall global score for memory and executive function.
Analysis of the activity tracker data showed that participants clocked up an average of 51 minutes of MVPA, five hours 43 minutes of light intensity physical activity and nine hours 16 minutes of sedentary behaviours over a 24-hour period.
Unlike previous studies, which have examined the link between daily MVPA and brain power, the new research also considered time spent asleep - which researchers say makes up the largest component of any 24-hour period.
Over the course of a day, participants slept for an average of 8 hours 11 minutes.
Time spent in MVPA relative to other types of behaviour was positively associated with cognitive performance after adjusting for educational attainment and workplace physical activity. But additional adjustment for health issues weakened these associations.
Sedentary behaviour relative to sleep and light physical intensity activity was also positively associated with cognitive performance - however researchers note that this trend likely reflects greater engagement in cognitively stimulating activities such as reading or working, rather than any apparent benefit from watching TV.
The associations were stronger for executive function than they were for memory.
When compared with the sample average, participants in the upper half of cognitive performance scores spent more time in MVPA and sedentary behaviours and less time sleeping, while the lowest 25% of scorers clocked up the most light intensity physical activity.
To better understand the connection between movement and cognition, the researchers reallocated time from one component (ie, light intensity activity, vigorous activity, being sedentary) to another, minute by minute, to estimate what impact this might have on global cognitive performance scores.
This revealed that, in theory, scores after MVPA were much higher than after other activities.
For example, individuals showed a 1.31% improvement in cognition ranking - compared to the sample average - after as little as nine minutes of sedentary activities were replaced with more vigorous activities. This was a positive trend which became far more substantive with much greater reductions in sedentary activities.
Similarly, there was a 1.27% improvement from replacing gentle activities or 1.2% from replacing seven minutes of sleep. These improvements also increased with greater exchanges of time.
Sedentary behaviour was also favourable for cognition score, but only after substituting it for 37 minutes of light intensity physical activity or 56 minutes of sleep.
However, participants' brain power began theoretically declining by 1-2% after just eight minutes of sedentary activities replaced MPVA. And cognition ranking continued to decline in line with greater declines in vigorous activity.
Meanwhile, replacing vigorous activities with six minutes of light intensity physical activity or seven minutes of sleep was linked with similar falls of 1-2% in cognition ranking.
Lead author, PhD candidate John Mitchell (UCL Institute of Epidemiology & Health), said: "MVPA is typically the smallest proportion of the day in real terms and the most difficult intensity to acquire. Perhaps partly for this reason, loss of any MVPA time whatsoever appeared detrimental, even within this relatively active cohort."
He added: "This robust method corroborates a critical role for MVPA in supporting cognition, and efforts should be made to bolster this component of daily movement."
Study limitations
This is an observational study, and as such, can't establish cause. The researchers also highlight various caveats: activity tracker measures can't provide context for each component of movement. And despite a large sample size, people of colour were underrepresented, limiting the generalisability of the findings.
