The Crossroads of Physical Activity, Sleep and Cognitive Decline

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The Guide * The Atmasvasth Guide to Living Long, Healthy - 15 Aug 2021 Understanding the Steps and Taking Control Taking Control * Atmagyan, Atmasurakshit, Atmanivaaran and Atmanirbar - the four Atmas to be Atmasvasth - 16 May 2021 * The Healthy 7 is also the Happy 7 - 13 Mar 2022 * Prev…

AtmasvasthBhavin Jankharia

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Three weeks ago, in my piece titled “Disease Hell…What Can We Truly Prevent or Control”, I mentioned that there are 5 diseases/illness that we want to prevent at all costs (strokes, heart attacks, cancers, losing one’s mind and falls-related fractures).

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Not losing your mind would be the fourth, after brain and heart attacks and cancer. Though you yourself may not be aware that you are sliding into dementia (which perhaps may be a blessing at times) there are no sure shot measures to reduce cognitive loss, short of physical activity, the food we consume and perhaps life-long learning and social connections.

One of the many issues with ageing is cognitive decline, which leads to loss of memory and a reduction in other mental abilities that eventually impact our daily lives and the lives of those around us. To repeat, the best ways to reduce the risk of cognitive decline are physical activity (PA),  sensible eating and good sleep. Education levels, lifelong learning, engaging in habits such as reading that keep our minds active, maintaining relationships with our near and dear ones and staving off social isolation and loneliness also help reduce the rate of cognitive decline.

Poor sleep is associated with an increased risk of cognitive decline. Optimal sleep (6-8 hours) helps reduce the accumulation of Alzheimer’s disease biomarkers, just as increased PA does. Two years ago, I wrote about a study by Huang and colleagues [1] that found that the ill-effects of poor sleep on all-cause mortality and specific-cause mortality (cancer, cardiovascular disease) could be reduced by increasing PA levels to as less as 600 METmins/week, which would amount to a single 60-75 minutes run per week…basically the sweet spot of a daily 30-45 minutes walk counterbalances the ill-effects of poor sleep. As I have kept saying…PA trumps poor sleep.

However, the authors did not address the issue of cognitive decline in their UK biobank cohort, which this new paper [2] headed by Mikaela Bloomberg, based on data from the English Longitudinal Study of Ageing, does. The authors looked at 8958 individuals between the ages of 50-95 at baseline and then followed them up over at least 10 years to see how PA, sleep and cognitive decline play out.

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In brief, those with poor sleep (less than 6 hours or more than 8 hours) had a more rapid cognitive decline than those with optimal sleep (6-8 hours). At baseline, those with high PA and optimal sleep had the best cognitive scores, compared to all other combinations (low PA, any sleep level) and there was no difference in cognitive levels in those with high PA even if they had poor sleep. But, on follow-up over 10 years, those who had poor sleep, even if they had high PA levels, had a faster deterioration of cognitive function, compared to those with optimal sleep and high PA, such that their cognitive levels (i.e. high PA, poor sleep) declined to the same levels as those with low PA, at the end of 10 years. Basically, we need both, optimal sleep and high PA to not lose our minds.

The good part is that the authors used a 6-8 hours window and not the 7-8 hours window traditionally used by “sleep” specialists, which then is its cause of stress, if we don’t fall in that range. This is important because it is easier to achieve 6 to 6 1/2 hours of good sleep as against longer periods, as we grow older. It also shows us that while PA trumps poor sleep when it comes to mortality per se, this does not seem to be true when it relates to cognitive decline.

What does this mean for you and I? In our atmasvasth quest to live long healthy, both physically and mentally, it is important that we do both; sleep optimally (6-8 hours) and be physically active (at least one 30-45 minutes brisk walk per day). This will significantly reduce our rate of cognitive decline and keep our cognitive reserves intact, or perhaps even build them up, especially if we start as early as possible in our lives to sleep well and be physically active.

Footnotes

1. Huang BH et al. Sleep and physical activity in relation to all-cause, cardiovascular disease and cancer mortality risk. Br J Sports Med. 2021 Jun 29:bjsports-2021-104046.

2. Bloomberg M et al. Joint associations of physical activity and sleep duration with cognitive ageing: longitudinal analysis of an English cohort study. Lancet Healthy Longev. 2023 Jul;4(7):e345-e353.