American Heart Association President, Mitchell S. V. Elkind, M.D., M.S., FAHA, FAAN, professor of neurology and epidemiology at Columbia University Vagelos College of Physicians and Surgeons and attending neurologist at NewYork-Presbyterian/Columbia University Irving Medical Center in New York, New York offers perspective via Zoom on EPI Lifestyle 2021 presentations P149, MP24 and MP67.
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"These studies, of course, are not without some limitations. The studies are associational, they're observational. They can't prove that TV watching is the reason for people to develop cognitive decline or dementia or that sedentary behavior makes brain regions shrink. There could be a lot of other things that are associated with behavior like sedentary behavior or TV watching that themselves could increase the risk of cognitive decline or change brain structure. For example, people who spend a lot of time sitting on a couch, watching TV may also eat in a less healthy way. They may consume a lot more alcohol or unhealthy beverages, sugar sweetened beverages, for example. So there's a lot of potential for confounding and the investigators tried to account for these differences as much as possible, but these are hard things sometimes to tease out completely. Also, it's interesting that the effects of sedentary behavior were not necessarily consistent across all of the different outcomes. So in the ERIC study, there was an effect on cognitive decline, measured using neuropsychological testing, but there wasn't a clear effect on the diagnosis of dementia. And this is always a controversial question. How much does a neuropsychological test reflect a diagnosis of dementia? If your test score has changed a little bit, is that as important for one's quality of life and ability to participate in usual daily activities as is frank dementia? So that's an outstanding question. Also, it's interesting that in the ERIC study, the effect on the brain matter of the brain, the cellular components of the brain was deep within the brain, whereas in the CARDIA study, it looked like that effect was on the surface of the brain. So I think we still need more confirmatory evidence from other studies, looking at these effects. The bottom line message though should be that for people to maintain their brain health as they age, particularly during a time when people may be forced to engage in more sedentary activities than usual, the idea is to try to maximize your activity level as much as possible because sitting still, sedentary behavior may not be good for the brain."