Sitting too long harms your brain

School, work, exams, crosswords: often when we are doing something that makes us use our brain capacities, we are sitting down. Our latest study However, we discovered that sitting too long can affect the supply of the brain and have a negative impact on its health.

Awhen it represents only 2% of our body weight, the brain requires 20% of our energy needs at rest. It is particularly greedy in glucose, its main fuel. An interruption of this supply may alter or even damage brain cells, and therefore have consequences on brain health.

Glucose levels too weak, But also too high, are likely to increase the risk of dementia. Finally, going from a high level to a low level of glucose also presents risks: a glycemic variability significant can cause a decrease in cognitive functions. Tight glucose control is therefore essential for the health of our brain.

Get up more!

Spending too much time sitting can increase the risk early death. It is estimated that if you remain in a sitting position for more than eight hours a day, 60 to 75 minutes of daily physical exercise are needed to compensate for this risk.

Which is a lot of time, at least twice as long as the minimum recommended adults. Thinking about getting up more regularly during the day can therefore be a strategy that pays off for your health.

Many studies have shown the benefits of low-intensity walking, especially after meals, on glucose control. This means that the glucose level, in this situation, does not rise too high, nor does it fall too low. This phenomenon could find its explanation in the fact that muscles in action spend part of the glucose present in our system, and therefore allow it to maintain an optimal level.

Hypothetical diagram showing glucose control after a meal, in a person who remains seated (above) and in a person who walks at low intensity (below).
Author provided / The Conversation, CC BY ND

Some work suggest that low-intensity physical activity spread over the day has more benefits on glucose control than short morning effort. And this even if the amount of energy expended is equivalent.

What effects on the brain?

So it is possible that this is all just a story of glucose regulation. But what about the effects on the brain?

The results of studies that have looked into the issue are mixed. The idea that a full day of sitting can, compared to another regularly interspersed with physical activity, have a negative impact on memory-related tasks, is supported by some laboratories. But others fail to corroborate it.

Why not work while standing? Unsplash / Grovemade, CC BY

Other studies have chosen to follow a large number of people for several years. And they suggest a link between time spent in a sitting position and impaired brain function. But it is difficult to draw conclusions, given the multitude of data measured. In general, those that do not ask participants to report their data themselves are more reliable. But sometimes it is difficult to do otherwise.

Walking sends blood to your brain

Other approaches exist, apart from that which consists in directly measuring the performance of participants on tasks that require them to use their brain. Researchers at the University of New Mexico Highlands have, for example, demonstrated that when we walk, the impact of the feet on the ground sends pressure waves through the blood vessels, resulting in increased blood flow to the brain.

However, this flow is linked to the regulation of the supply of glucose to the brain. Its variation can therefore have effects on the health of our brain. We know for example that a drop in blood flow in the brain accelerates the loss of brain function in people with Alzheimer's disease.

What solutions?

For scientists, the link between sitting and impaired brain function is a real challenge. Studies carried out so far tend to show that reducing the time spent in a sitting position does tend to slow the decline of cognitive functions, but does not improve them.

For the rest of the population, and even if the scientific conclusions are still uncertain, you are already advised spend less time sitting, especially after meals: poor glucose regulation can have other adverse health effects.

The ConversationSo, feel free to go for a walk after lunch, wash the dishes by hand after dinner, walk or cycle to work. There are plenty of options to avoid sitting still throughout the day, and your health will be better.

Michael wheeler, PhD Candidate in Exercise Physiology, University of Western Australia; Daniel Green, Winthrop Professor, University of Western Australia; David Dunstan, Professor and Laboratory Head of Physical Activity, Baker Heart and Diabetes Institute, and Paul Gardiner, Postdoctoral Research Fellow in Healthy Aging, The University of Queensland

La original version of this article was posted on The Conversation.

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