Work at a desk all day? Sitting too long linked to thinning of brain region critical for memory, study suggests

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Long periods of sitting have been linked to a variety of health issues, including higher risk of heart disease, diabetes, muscle wasting and premature death.

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Now, researchers from the University of California-Los Angeles' Semel Institute and its Center for Cognitive Neuroscience have found that sedentary behavior is a "significant predictor of thinning of the medial temporal lobe."

The medial temporal lobe, which includes the hippocampus, is the region of the brain critical for new memory formation. Medial temporal atrophy, such as thinning, has been associated with memory loss and has been used to predict Alzheimer's disease, according to Dr. Joe Nocera, an assistant professor in neurology at Emory University who was not involved in the UCLA study.

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“What’s interesting is that there’s more and more people referring to sitting a lot as the new smoking,” Nocera said about the new research. He added that most people would agree about the positive effects of exercise from the neck down, but growing literature demonstrates robust positive effects related to brain health as well.

For the study published in the April 12 issue of the Public Library of Science One, researchers recruited 35 people (25 women and 10 men) ages 45-75 and recorded their physical activity levels as well as the average number of hours per day they spent sitting during the previous week.

Each participant also underwent a high-resolution MRI scan that offered a detailed look at the medial temporal lobe.

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The researchers discovered that participants who spent the most time standing up and moving had plumper medial temporal lobes.

Study subjects reported average sitting times of three to 15 hours per day. After adjusting for age, the researchers found that one additional hour of daily sitting was associated with a two percent decrease in the thickness of the medial temporal lobe.

In addition to noticing sedentary behavior as a predictor of thinning in the medial temporal lobe, researchers also found that even high physical activity couldn’t cancel out the harmful effects of sitting too much.

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"Of course, we need larger samples and better ways to measure patterns of sedentary behavior," lead author Prabha Siddarth told the Los Angeles Times. "But if you're sitting for long periods of time, it seems that that factor — not physical activity — becomes the more harmful or more significant measure of your fitness. Even for people who are physically active, sitting a lot seems to be bad for your brain."

This study does not prove that too much sitting causes thinner brain structures, the authors noted. But the findings reveal that more hours spent sitting are associated with thinner regions.

The UCLA team hopes to follow a group of people for much longer to determine if sitting does in fact, cause thinning of the medial temporal lobe and whether gender, weight or race play a role.

According to Nocera, smoking and alcohol use could also factor into the association. The exclusion of reporting smoking and drinking habits, the self-reporting of exercise and fitness habits as well as the study’s small sample size, were some significant limitations of the research, he said.

In the meantime, for those working sedentary jobs, Siddarth recommends getting up every now and then and pacing around, or even taking a walk during lunch time. It may help to set alarms or phone reminders.

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