Sitting harms brain health, regardless of exercise
Sitting harms brain health, A preliminary study of middle-aged and older individuals suggests that excessive seating may be detrimental to the health of the brain.
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Sitting harms brain health, A preliminary study of middle-aged and older individuals suggests that excessive seating may be detrimental to the health of the brain.
Researchers from the University of California, Los Angeles (UCLA) discovered that among 35 individuals aged 45–75 without dementia, the medial temporal lobe was thinner in those who spent more time seated during the day.
This region of the brain is essential for forming new memories.
In a report on their findings published in the journal PLOS ONE, the authors conclude that even high levels of physical activity made no difference.
Even among physically active individuals, excessive sitting may increase the risk of cardiovascular disease, diabetes, and other diseases, as suggested by this study.
David Merrill, an assistant clinical professor of psychiatry and biobehavioral sciences at the University of California, Los Angeles, and colleagues propose conducting additional research to determine whether limiting sedentary behavior reverses the effect they observed.
In the study's introduction, the authors cite the growing body of research suggesting that physical activity may delay the onset of Alzheimer's disease and other dementias and can improve brain structure.
One proposed explanation for this effect is that physical activity increases brain blood flow, which in turn promotes the development of new nerve cells and counteracts the decline in structure and function.
In contrast to the volume of literature on the effects of exercise, however, "there is a paucity of research on the relationship between sedentary behavior and dementia risk," and the authors observe that few studies have examined the "mechanistic" influence on the brain.
This should be a cause for concern, they argue, given that approximately 13 percent of the global burden of Alzheimer's disease may be attributable to excessive sitting.
On the basis of this estimation, they conclude that a 25 percent reduction in sedentary behavior "could potentially prevent more than 1 million" cases of Alzheimer's disease worldwide.
The team chose to concentrate on the medial temporal lobe because it is known that this region of the brain deteriorates with age, resulting in memory impairment.
In addition, they observe that increased "aerobic fitness" correlates with a larger hippocampus, a region of the medial temporal lobe that has been "heavily studied" and is essential for memory.
In their study, the researchers examined the relationship between the thickness of the medial temporal lobe, physical activity, and seated time in 25 women and 10 men aged 45 to 75 without dementia symptoms.
Men and women completed in-depth questionnaires that yielded information on the average number of hours spent seated daily and their levels of physical activity. The girth of the medial temporal lobe was measured using MRI scans of their skulls.
The researchers discovered "no significant correlations" between levels of physical activity and medial temporal lobe thickness after analyzing the data.
However, they did find that the more sedentary people had less medial temporal lobe thickness.
While the authors did not investigate the mechanisms by which prolonged sitting may be harmful to the brain, they note that "sedentary behavior may have deleterious effects on glycemic control."
They hypothesize that this could increase the variability of blood sugar and reduce blood flow to the brain, thereby impairing brain health.
In addition, they note that their findings are "preliminary" and do not prove that protracted seating causes the medial temporal lobe to thin. They suggest that:
Future research should include longitudinal analyses and investigate mechanisms as well as the efficacy of reducing sedentary behaviors in order to reverse this association.
