Blog Short #119: Sitting is Bad For Your Brain

Photo by Marilyn Nieves, Courtesy of iStock Photo

We’re a culture that sits a lot, and it’s hurting our brains. We work on computers at our desks, sit and scroll endlessly through our phones, and plop down on the couch at night to watch TV.

According to a study published by the CDC in 2018, about 25% of adults over 18 sit for more than 8 hours per day. Of those, 44% engage in moderate to vigorous physical activity each week, and about 11% sit for more than 8 hours a day and do little leisure-time physical activity. Only 3% sit for less than 4 hours per day and are physically active (Ussery et al., 2018).

Another article published by The Washington Post cited a study concluding that:

The average American adult spends about 6.5 hours sitting every day, and teens ages 12 to 19 spend 8 hours.

Today I’m summarizing some of the most alarming repercussions and the recommendations to counteract them. This subject is a little out of the realm of psychology, but body and mind are closely linked, so it’s good to pay attention to both.

Let’s start with the repercussions.

What happens when you sit most of the day?

1. You reduce blood flow to your brain.

Decreased blood flow to the brain is associated with decreased cognitive functioning and increased risk for neurodegenerative diseases like Parkinson’s and Alzheimer’s.

One study followed a small group of people who had day jobs where they sat much of the time. The volunteers came to the lab on three different occasions and sat for four hours. On the first day, they sat and only got up if they needed to use the restroom. The second day, they got up every 30 minutes and walked on a treadmill for 2 minutes. On the third day, they sat for two hours, got up, walked on the treadmill for 8 minutes, and sat for another two (Carter et al., 2018).

In all three situations, blood flow to the brain was reduced while sitting. However, it was restored to normal when walking on the treadmill. But the best results were for the second group, who exercised for two minutes every half hour.

A similar study used 8-hour segments instead of four but measured blood pressure and blood sugar spikes. They found that five minutes of walking every 30 minutes reduced blood sugar spikes by 60% and blood pressure by four to five points (Duran et al., 2023).

Why does walking help?

Because our leg muscles are the largest muscles in our body, and when we’re not working them, they’re not taking in fuel from the bloodstream and not releasing substances that break down fatty acids in our blood. This causes a slowing of our metabolism and increased blood sugar and cholesterol (Field, 2021).

“People with high blood sugar, regardless of whether they are technically diabetic, have a faster rate of cognitive decline than those with normal blood sugar.” (Gupta, 2021, p. 109).

So sitting all day most days puts us at risk for cognitive decline, cognitive disease, and diabetes.

2. Your risk for cardiovascular disease increases.

Many studies have examined the relationship between extended sitting and cardiovascular disease. The overall conclusion is that there’s a substantial correlation between the two, but there are differences about whether or not physical activity, exercise in particular, has a preventative effect. Most say yes, but others say you need to reduce sitting time regardless of how much you exercise (Henschel et al., 2020).

What is clear is that sitting for long periods is bad for your heart, and one study found that sitting while watching TV was particularly harmful.

3. Your memory’s impaired.

Now for memory.

Extended sitting has been linked to thinning of the brain’s medial temporal lobe. The MTL is the region of the brain associated with memory formation (Siddarth et al., 2018).

Our brains mature at around 25 years of age. However, memory starts to erode at age 24. Quite the paradox!

Most people don’t notice significant memory decline until their 50s and 60s, but a slow shift in the mid-20s continues to gain traction over the next few decades. Sitting and a sedentary lifestyle can hasten that decline.

4. Your susceptibility to depression increases.

A meta-analysis of 49 studies focusing on the effects of physical activity on depression concluded that people who were sedentary had a greater chance of becoming depressed as well as staying depressed (Schuch et al., 2018).

In almost all of the studies, regular exercise significantly reduced the incidence of depression and improved mood for those already depressed.

5. You reduce your capacity for learning.

I’ve already mentioned cognitive decline as a danger associated with extensive sitting and a sedentary lifestyle. Learning is a specific cognitive activity that can suffer as a result of sitting too much.

Learning requires:

1. Increased production of neurons (brain cells),
2. Increased connections between neurons (synapses),
3. And protection for the lifespan of existing neurons.

BDNF, or Brain-Derived Neurotrophic Factor, enables all three of these processes. BDNF is a protein that’s been described as “Miracle-Gro” for the brain (Ratey, 2008).

Here’s the important part:

BDNF is released by the brain when we move our bodies, as in aerobic exercise. When you exercise regularly, your BDNF acts to grow new neural networks to facilitate learning. When you sit most of the time, this process is hampered, and learning slows.

What to Do

Let’s go over the specific recommendations. From what we’ve uncovered so far, exercise is the primary recommendation. A second recommendation is to reduce sitting time.

1. Get up and move every 30 minutes. If you sit for hours at a time, you should get up and exercise for at least three minutes every half hour. Exercise can be a quick walk, calisthenics, or anything to get your blood flow back up to speed.
2. Stand more. Stand-up desks are increasingly showing up in offices as people try to reduce sitting time. A key consideration would be ergonomics if you’re typing on a computer, but often stand-up desks are adjustable. If you’re a heavy TV watcher, it’s good to get up during the commercials or at least stand.
3. Do aerobic exercise. Options are walking, jogging, swimming, or playing a sport like tennis. The goal is to get your heartbeat up, take in more oxygen, and exercise your leg muscles to increase blood flow and regulate insulin.

Other significant benefits of regular aerobic exercise are:

• An increase in BDNF to increase learning capacity
• Increases in serotonin to stabilize mood and prevent depression
• Increases in dopamine to promote focus, attention, drive, and impulse control
• Raising your threshold for stress and reducing overall reactivity
• Reducing anxiety

In addition to doing three minutes of exercise per half hour of sitting, you should aim to do at least 150 minutes of aerobic exercise per week.

In this case, more is better. Walking works! You get more protection against cognitive decline and memory impairment with the more aerobic exercise you do.

Other General Recommendations

• Use stairs when you can.
• Park further away from the store when grocery shopping.
• Monitor your daily steps with a step counter and shoot for 10,000.
• Garden or do outside work more.
• Walk on lunch breaks.
• Do strength training.
• Walk around while on the phone.

Do What You Can

We all know exercise is good for us, but time is a consideration. Do the best you can to incorporate any of these strategies, and as always, start slow and build until habits are in place.

An aside – I tried walking for three minutes in my house every half hour while writing this blog. It took some getting used to, but I did get some good effects.:) It cleared my mind and got the blood flowing. Let me know how it goes for you!

That’s all for today.

Have a great week!

All my best,

Barbara

_FOOTNOTES

_{Carter, S. E., Draijer, R., Holder, S. M., Brown, L., Thijssen, D. H. J., & Hopkins, N. D. (2018, September 19). Regular walking breaks prevent the decline in cerebral blood flow associated with prolonged sitting.  Journal of Applied Physiology 125: 790-798. https://doi.org/10.1152/japplphysiol.00310.2018}

_{Duran, A. T., Friel, C. P., Serafina, M. A., Ensari, I., Cheung, Y. K., & Dias, K. M. ( 2023, January 12). Breaking up prolonged sitting to improve cardiometabolic risk: Dose-response analysis of a randomized cross-over trial. Medicine & Science in Sports & Exercise. DOI:10.1249/mss.0000000000003109}

_{Field, B. (2021). How sitting harms your brain and overall health. Very Well Mind.
https://www.verywellmind.com/how-sitting-harms-your-brain-and-overall-health-5202403}

_{Gupta, S. (2021). Keep sharp: Build a better brain at any age. Simon & Schuster.}

_{Henschel, B., Gorczyca, A. M., & Chomistek, A. K. (2020). Time spent sitting as an independent risk factor for cardiovascular disease. American Journal of Lifestyle Medicine, 14(2), 204-215. https://doi.org/10.1177/1559827617728482}

_{Hörder, H., Johansson, L., Guo, X., Grimby, G., Kern, S., Östling, S., & Skoog, I. (2018, April 10). Midlife cardiovascular fitness and dementia: A 44-year longitudinal population study in women. Neurology. 90(15): 1298-1305. DOI: https://doi.org/10.1212/WNL.0000000000005290}

_{Loehngen, E. (2020, September 21). How sitting affects the brain and the mind. Walkolution. https://walkolution.com/blogs/science/sitting-brain-mind}

_{Ratey, J. (2008). Spark: The revolutionary science of exercise and the brain. Little, Brown Spark.}

_{Schuch, F. B., Vancampfort, D., Firth, J., Rosenbaum, S., Ward, P. B., Ph.D., Silva, E. S, Hallgren, M., Ponce De Leon, A., Dunn, A L., Deslandes. A. C., Fleck, M. P., Carvalho, A. F., & Brendon Stubbs, B. (2018, July). Physical activity and incident depression: A meta-analysis of prospective cohort studies. American Journal of Psychiatry, 175(7), 632-648. https://doi.org/10.1176/appi.ajp.2018.17111194}

_{Searing, L. (2019, April 28). The big number: The average U.S. adult sits 6.5 hours a day. For teens, it’s even more. The Washington Post.
https://www.washingtonpost.com/national/health-science/the-big-numberthe-average-us-adult-sits-65-hours-a-day-for-teens-its-even-more/}

_{Siddarth, P., Burggren, A. C., Eyre, H. A., Small, G. W., & Merrill, D. A. (2018). Sedentary behavior associated with reduced medial temporal lobe thickness in middle-aged and older adults. PLOS ONE, 13(4), e0195549. https://doi.org/10.1371/journal.pone.0195549}

_{Ussery E.N., Fulton, J. E., Galuska, D. A., Katzmarzyk, P. T, & Carlson, S. A. (2018, November 20). Joint prevalence of sitting time and leisure-time physical activity among US adults, 2015-2016. Journal of the American Medical Association, 320 (19): 2036-2038. doi: 10.1001/jama.2018.17797 https://jamanetwork.com/journals/jama/fullarticle/2715582}