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Hours of sitting can restrict blood flow to the brain. This finding from recent research may have implications for long-term brain health.
Sitting at Work
Naturally, we have been concerned for decades about the consequences of prolonged sitting at work. Sitting in the office for eight hours or more a day means a significant portion of time that could have been spent being active. This is especially concerning regarding the amount of exercise needed to reduce the risk of obesity and cardiovascular diseases.
Just last month, I wrote about ‘active sitting.’ This was in response to researchers who wanted to find out if some effects of sitting could be mitigated by continuing to use certain muscles. This could limit the stiffening of veins, one of the potential consequences of prolonged sitting.
Hours of sitting can also restrict blood flow to the brain, as revealed by research among office workers. Standing up and moving for two minutes every half hour could help prevent this.
Sitting and Blood Flow
The transportation of blood to the brain is one of the automated internal processes. Although we are not consciously aware of it, it is an essential process for life and consciousness. Brain cells simply need the oxygen and nutrients provided by blood. Several major arteries are continuously sending blood to the head.
This supply is strongly regulated due to its great importance. Various physiological signals are monitored for this purpose, such as the amount of carbon dioxide in the blood. This is intended to ensure that the level of supply remains within a certain range.
However, small fluctuations occur, both sudden and lingering. Previous studies in humans and animals have shown that small, brief reductions in blood flow to the brain can impair cognitive function and memory. Longer-term decreases have been associated with a higher risk of neurodegeneration, including dementia.
Other research has shown that prolonged sitting limits blood flow to various parts of the body. Most of these studies focused on the effects on the legs, primarily because they are most affected by posture, both sitting and standing.
Blood Flow to the Brain
However, it was unknown whether this effect also occurs in the brain. Researchers from John Moores University in England wanted to change that [1].
They worked with 15 healthy men and women who perform office work. People accustomed to sitting for hours. They asked office workers to come to the university’s performance lab three times. Each day, they received special headbands with ultrasound sensors that could measure blood flow in the middle cerebral arteries, important suppliers of oxygen-rich blood to the brain.
In addition, the amount of carbon dioxide at the beginning of each session was measured through the participants’ breath. This allowed the researchers to see if and to what extent carbon dioxide was responsible for any fluctuations in blood flow. The amount of carbon dioxide in the blood can be influenced by various factors, including changes in breathing.
After this measurement, the participants in one of the sessions engaged in a simulation of office work. They sat at a desk for four hours, reading or working on a computer. They only stood up to go to the nearby toilet.
In another session, they were instructed to stand up and walk on a treadmill next to the desks for two minutes every 30 minutes. They did this at an average walking pace slightly faster than 3 km/h.
In the last session, they only stood up once, after two hours of sitting. However, they walked for eight minutes at the same pace.
Go Get Your Own Coffee
Blood flow and carbon dioxide levels were measured immediately before and during the walks. They were also measured at the end of each session.
As expected, blood flow decreased when participants sat uninterrupted for four hours. This effect did not occur in the session where they walked for two minutes every 30 minutes. Walking for eight minutes every two hours did not have this protective effect.
I think relatively few people stay seated for four hours at work, interrupted only by visits to a (nearby) toilet. At least, I don’t. For me, it could be somewhere between half an hour and two hours. Standing up every half hour for two minutes is also not always ideal when you’re trying to finish something. Further research, such as examining the effects of standing up and walking every hour, would make it easier to determine whether and to what extent you should adjust your own routine.
This research might be helpful if you have a boss who’s a slave driver.
References
- Carter SE, Draijer R, Holder SM, Brown L, Thijssen DHJ, Hopkins ND. Regular walking breaks prevent the decline in cerebral blood flow associated with prolonged sitting. J Appl Physiol (1985). 2018 Jun 7. doi: 10.1152/japplphysiol.00310.2018. [Epub ahead of print] PubMed PMID: 29878870.
