People who spend more time sitting or engaged in sedentary behavior have thinner brain structures in a region of the brain associated with memory, according to a study newly published in the journal PLOS One.
Thinning in this part of the brain could be a precursor to cognitive decline, dementia, or Alzheimer's, according to the researchers.
Unfortunately, they wrote in the study that high levels of physical activity aren't enough to offset the effects of that sedentary behavior.
The UCLA scientists behind the new research recruited 35 healthy middle-aged and older adults between the ages of 45 and 75. Researchers asked about the participants' physical-activity levels and about how much time they spent sitting during the work week.
To assess people's brain health, the researchers conducted high-resolution MRI scans of the participants' brains so they could get a close look at the medial temporal lobe (MTL) — a brain region important for memory formation.
Contrary to what some previous researchers have found, the amount of exercise study participants got didn't seem to have a significant effect on MTL thickness. But sedentary behavior did.
On average, the participants sat between three and seven hours per day. But the more people sat, the thinner their MTL and connected sub-regions of the brain tended to be. Thinning in this brain region can be a sign of cognitive decline, the researchers said in a statement. Reducing sedentary behavior may therefore be a way to improve brain health in people at risk for Alzheimer's.
A few caveats to note: this isn't a particularly large study, and since the researchers just assessed participants at one point in time, they can't be sure that the brain thinning was caused by sedentary behavior (just that the two were connected). But the fact that more sedentary behavior was associated with more thinning implies that there could very well be a causal connection.
In follow-up studies, the researchers would like to follow a group over time to better understand if sitting is causing the thinning and if other demographic or behavioral factors play a role. They also need to see if getting up and walking around — taking a break from sitting — makes a difference in terms of MTL thickness.
In the meantime, the researchers suggest that reducing sedentary behaviour may provide cognitive benefits. So if you can find a way to make your lifestyle more active, give it a shot.