Maintaining exercise routines throughout adulthood can help to preserve mental acuity and memory

Categorising physical activity levels

Physical activity is modestly associated with a lower risk of dementia, cognitive decline, and loss of later life mental acuity. But it’s not known whether the timing, frequency, or maintenance of leisure time physical activity across the life course might be key to later life cognitive abilities.

Dr James and her team wanted to know if physical activity might be most beneficial in specific ‘sensitive’ periods during the life course, or across a number of time periods. They looked at the strength of associations between a range of cognitive tests at age 69 and reported leisure time physical activity at the ages of 36, 43, 53, 60-64, and 69 among 1,417 people (53 per cent of whom were women) taking part in the 1946 British birth cohort study.

Physical activity levels were categorised as: inactive; moderately active (1-4 times/month); most active (5 or more times/month), and summed across all five assessments to create a total score ranging from 0 (inactive at all ages) to 5 (active at all ages). 

Some 11 per cent of participants were physically inactive at all five time points; 17 per cent were active at one; 20 per cent were active at two and three; 17 per cent were active at four and 15 per cent at all five.

Cognitive performance at age 69 was assessed using the validated ACE-111, which tests attention and orientation, verbal fluency, memory, language, and visuospatial function, plus by tests of verbal memory (word learning test) and processing speed (visual search speed).

Factors associated with a heightened risk of cognitive decline – cardiovascular and mental health, and carriage of the APOE-ε4 gene – were also assessed to see if these modified any observed associations. 

Being active at five 'time points' was linked to best results

Analysis of the results showed that being physically active at all five time points was associated with higher cognitive performance, verbal memory, and processing speed at the age of 69. 

The effect sizes were similar across all adult ages, and for those who were moderately and most physically active, ‘suggesting that being physically active at any time in adulthood, even if participating as little as once per month, is linked with higher cognition’, Dr James and her team note. 

But the strongest association was observed for sustained cumulative physical activity and later life cognition, and for those who were most physically active at all ages.  This positive association between cumulative physical activity and later life cognitive performance was explained, in part, by childhood cognition, socioeconomic position and education. 

The effect remained significant when these were factored in, and the associations weren’t explained by differences in later life cardiovascular or mental health.

‘Together, these results suggest that the initiation and maintenance of physical activity across adulthood may be more important than the timing … or the frequency of physical activity at a specific period,’ say the researchers.

Our findings ... provide evidence that encouraging inactive adults to be more active at any time, and encouraging already active adults to maintain activity, could confer benefits on later life cognition [Sarah-Naomi James et al]

Limitations

Being an observational study cause cannot be established, and the researchers acknowledge a number of limitations. The study included only white participants and had a disproportionately high attrition rate among those who were socially disadvantaged. No information was available on exercise intensity, duration, or adherence either.

Conclusion

But the authors nevertheless conclude: 'Our findings support guidelines to recommend participation in any physical activity across adulthood and provide evidence that encouraging inactive adults to be more active at any time, and encouraging already active adults to maintain activity, could confer benefits on later life cognition.’

To see a full version of the paper – titled Timing of physical activity across adulthood on later life cognition: 30 years follow-up in the 1946 British birth cohort doi 10.1136/jnnp-2022-329955 – visit: https://jnnp.bmj.com/lookup/doi/10.1136/jnnp-2022-329955