Why Sitting Might Harm Your Brain

by Baxter

The Chair by Salvador Dali*

Most of us have received the memo by now that sitting is the new smoking! Today, I will share with you a new study that may provide you with one more reason to get you up out of that chair frequently, whether at work or elsewhere. Although the study I will review looked at a workplace setting, Ram has noted previously that “sedentary activities include the time spent sitting in an automotive on a long commute, sitting at a desk at work, sitting on the couch after work, watching television, reading, and playing games or surfing the internet.” And the average American adults spends an impressive 10-12 hours sitting each day in these ways, with surveys of other countries around the world pointing to similar trends. So, this topic is likely relevant for all of us! 

There are a few other points I feel are worth revisiting from past posts before we get to this new study. So, let’s start with a review of what we already know from those posts. I’ll then discuss a new study that showed why sitting might be bad for the health of your brain.

What We Already Know 

How does sitting specifically affect health?

Sitting is right behind smoking in contributing to shortening your lifespan, even ahead of high blood pressure and high cholesterol. In the study Patterns of Sedentary Behavior and Mortality in U.S. Middle-Aged and Older Adults: A National Cohort Study that demonstrated this, which Nina discussed in our post Pop Upright for Even a Minute or Two, it was also noted that getting up every 30 minutes and moving—even if your overall time sitting was similar to non-standers—lowers your risk of early death. 

Prolonged sitting is also associated with many other health issues, such as obesity, high blood pressure, cardiovascular disease, osteoporosis, and several types of cancer. In addition, it affects the structure of the body, negatively impacting the spine, neck and hips.

Maybe as important to keep in mind is that there is research that shows that even if you exercise regularly outside of the 8-10 hrs of sitting you may be doing for work, it does not undo the ill effects of prolonged uninterrupted sitting! (See Sitting time and all-cause mortality risk in 222 497 Australian adults.) 

How does sitting specifically affect cognition? 

From another study Acute effects on cognitive performance following bouts of standing and light-intensity physical activity in a simulated workplace environment, which Nina reviewed previously in Pop Upright for Even a Minute or Two, we know that standing frequently and light physical activity in the workplace improves overall short-term cognitive function. 

What is the effect of decreased blood flow to the brain in the short term and over time? 

We know that sudden, complete disruption of blood flow to the brain, that is, stroke, can permanently damage parts of the brain and in some instances result in sudden death. But strokes are typically cause by a blocked or ruptured blood vessel. We don’t know, however, if being sedentary, our topic of today, can cause a stroke, but it can contribute to the development of cardiovascular disease, which increases your chance of strokes.

In Brain, Aging, and Cognition, Ram points out that cognitive changes we experience with age, such as memory loss, are in part related to an overall decrease in blood flow to the brain, often as a result changes to the circulatory system of the brain, such as narrowing of the blood vessels. This low flow state can cause cell death and therefore diminished function in the affected areas. However, we are still uncertain of the effects of small, intermittent decreases in blood flow, such as from sitting, at this time. 

About the Latest Study on Blood Flow to the Brain

An August 15th, 2018 article in the New York Times Why Sitting May Be Bad for Your Brain discussed the results of a new study, which adds yet another potential reason for us to get up regularly when sitting for long periods of time. The study measured changes in blood flow to the brain in three different scenarios, which I will discuss below. But generally regarding the importance of steady blood flow to the brain, the Times noted:'

“Past studies in people and animals indicate that slight, short-term drops in brain blood flow can temporarily cloud thinking and memory, while longer-term declines are linked to higher risks for some neurodegenerative diseases, including dementia.” 

They also note that past research has demonstrated that long periods of sitting decreases blood flow to the legs, but no studies had been down to date to look at blood flow to the brain. 

To try and find out about the effect of prolonged sitting on blood flow to the brain, researchers in England studied 15 healthy adults, both men and women, who worked jobs that involved long periods of sitting (see Regular walking breaks prevent the decline in cerebral blood flow associated with prolonged sitting). The researchers used an ultrasound machine to track the blood flow through the middle cerebral artery, one of the brain’s main arteries, and also monitored the carbon dioxide (CO2) levels in the subjects' exhalations to see if that might correlate with any blood flow changes. Subjects were monitored in three separate situations:

1. Sitting for 4 hours straight, either reading or doing computer work, and only getting up when using a bathroom close by if needed
2. Sitting for 30-minute intervals doing the same work and getting up and walking on a treadmill machine next to their desks for 2 minutes at a comfortable pace, over the 4 hours.
3. Sitting for 2 hours doing the same work, with an 8-minute walk on the treadmill at the same comfortable pace as in the second scenario, over the 4 hours. 

The subjects had their blood flow and CO2 levels checked right before and during each movement break and at the end of 4 hours. What did the researchers discover? The sessions of 4 hours of straight sitting resulted in a small but noticeable decrease in blood flow by the end of the session. For the times when subjects sat for 2 hours, the blood flow increased during the 8-minute exercise session, but was lower at the end of 4 hours than at the start. Most impressively, overall blood flow was higher at the end of 4 hours when a 2-minute break occurred every 30 minutes. (CO2 levels remained the same in all groups in all settings, so was not apparently affecting blood flow.)

Now, this was a small study, which always affects the certainty of conclusions that came be made from the results. The study also did not test whether the changes in blood flow affected short-term cognitive function or tell us anything about the long-term impact of such decreases in blood flow on overall mortality and the development of the disease mentioned earlier. So, there is obviously more research needed both on larger groups of people and to answer questions. 

So, what’s the takeaway? Despite the limitation of the study, I feel it confirms certain recommendations we have made here regarding how to address long spells of sitting, such in our post Pop Upright for Even a Minute or Two, which recommends taking a break every 30 minutes. And we may want to consider updating other recommendations we have made in the past, such as those made in The Ill Effects of Prolonged Sitting to simply move 10 minutes for every hour of sitting. I recommend that instead of taking a 10-minute break every hour that you take a 2-minute break (or slightly longer) every 30 minutes.

Yoga asana can be a great movement break and is much less expensive than having a treadmill next to your desk! So I recommend for your two minute breaks either doing one static standing pose or two, as Nina suggests in her post Rethinking Office Yoga post or some simple dynamic versions of those poses to create as slightly more aerobic effect. And a great follow-up study for us yoga practitioners would be identical to this British one but using yoga breaks instead of treadmill ones.

Oops, there’s my timer telling me I’ve been sitting for 30 minutes! Time for me to get up and move for two minutes before getting back to work.

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