(CN) — Bad news for people who picked up a habit of binge-watching their favorite shows during the Covid-19 pandemic: three new studies link watching TV for moderate to high amounts of time throughout midlife to greater cognitive decline in later years, regardless of whether a person exercises regularly.
The findings will be presented Thursday at the American Heart Association’s virtual Epidemiology, Prevention, Lifestyle & Cardiometabolic Health Conference.
“This research is very timely and important in the midst of the current Covid-19 pandemic because we know people are spending more time engaging in sedentary behaviors such as watching television while being in quarantine,” American Heart Association President Mitchell S.V. Elkind said in a statement. Dr. Elkind is a professor of neurology and epidemiology at Vagelos College of Physicians and Surgeons and the Mailman School of Public Health, and attending neurologist at New York-Presbyterian/Columbia University Irving Medical.
“These are interesting correlations among television viewing, cognitive decline and brain structure,” Elkind said. “Television watching is just one type of sedentary behavior yet it’s very easy to modify and could make a big difference in maintaining and improving brain health.”
Cognition includes a person’s ability to remember, think, reason, communicate and solve problems. With life expectancy increasing in the United States among an aging population with multiple factors that do not support a healthy brain, experts believe cognitive impairment and dementia will likely rise.
“While studies have shown the benefits of exercise to support brain health, less is known about the potential consequences of prolonged sedentary behavior such as television viewing on brain structure and function,” Kelley Pettee Gabriel, lead author of one of the studies and a professor of epidemiology at the University of Alabama at Birmingham's School of Public Health, said in a statement.
“Engaging in healthy behaviors during midlife, between ages 45-64 years in the context of the study, may be important factors to support a healthy brain later in life,” Gabriel said.
More than 7 million new dementia cases are diagnosed worldwide every year. By 2050, dementia rates are expected to increase by 116% in wealthier countries and 264% in low-income countries.
“There are currently no medications available to cure or stop dementia. However, a recent report showed that nearly 40% of worldwide dementia diagnoses may be prevented or delayed by modifying 12 risk factors including exercise,” said Priya Palta, lead author of the second study and assistant professor of medical sciences and epidemiology at Columbia University Vagelos College of Physicians and Surgeons in New York City.
In their studies on the effects of sedentary behavior during midlife on brain health, Palta and Gabriel led teams to examine television viewing information collected in midlife from a subset of participants from the Atherosclerosis Risk in Communities Study and its Neurocognitive Study.
Participants were asked how much television they watched in their leisure time. Their self-reported responses were not based on specific hours but rather on the classifications of never or seldom (low), sometimes watched TV (medium/moderate), and often/very often watched TV (high).
The focus of Palta’s study that included 10,700 adults of the median age of 59 was on cognitive decline and the risk of dementia, while Gabriel’s study of 1,601 adults of the median age of 76.2 years focused on structural brain markers from brain imaging scans.
Over two decades of the study, Palta and her team measured working memory, language, and executive function/ processing speed in study participants.
Palta found that compared with people who reported they never or seldom watched TV, participants who reported sometimes or frequently watching TV had a 6.9 % greater decline in cognitive function over 15 years, even though high amounts of TV viewing were not notably associated with higher dementia risk and reported exercise habits did not appear to change the relationship between time spent watching TV during midlife and changes in cognitive function and dementia risk.
Gabriel’s study meanwhile used MRI brain scans to track changes in structural brain markers, including deep gray matter volume in the brains of each participant. Gray matter is the darker tissue of the brain and spinal cord and is involved in muscle control, seeing and hearing, decision-making and other important brain functions. The higher a person’s volume of brain gray matter, the better cognitive skills they will typically have.
Gabriel’s team found that compared with participants who said they seldom or never watched TV, those who reported watching moderate or high amounts of TV had lower volumes of deep gray matter more than 10 years later in life, indicating greater brain atrophy and deterioration.
As with Palta’s study, physical activity and exercise habits did not change the associations between the level of television viewed during midlife and measures of gray matter in brain structure.
“Our findings suggest that the amount of television viewing, a type of sedentary behavior, may be related to cognitive decline and imagine markers of brain health. Therefore, reducing sedentary behaviors, such as television viewing, may be an important lifestyle modification target to support optimal brain health,” Palta said.
Ryan Dougherty, a postdoctoral fellow in the department of epidemiology at the Johns Hopkins Bloomberg School of public health in Baltimore, is the lead author of the third study.
Dougherty’s study also found a correlation between TV watching and the volume of gray matter in the brain, though it focused on younger adults.
“In the context of cognitive and brain health, not all sedentary behaviors are equal; non-stimulating sedentary activities such as television viewing are linked to greater risk of developing cognitive impairment, whereas cognitively stimulating sedentary activities (e.g., reading, computer and board games) are associated with maintained cognition and reduced likelihood of dementia," Dougherty said.
He added, “Considering the contextual differences in varying sedentary behaviors is critical when investigating cognitive and brain health."
Investigators in Dougherty’s study evaluated data from a separate but related study, the Coronary Artery Risk Development in Young Adults study, that began in 1985-86 with 5,115 people.
During the 20-year study in which participants were a mean age of 30 at the start, they took five-year check-ins to evaluate cognitive structure and health.
Dougherty and his team found that greater TV watching in early to mid-adulthood was associated with lower gray matter volume 20 years later.
A one-hour greater mean television time was associated with approximately a 0.5 % decrease in gray matter volume, which is similar to the annual rate of atrophy throughout mid-late adulthood, the study found.
As with the two previously mentioned studies, Dougherty’s study found that physical activity and exercise habits did not impact the association between TV watching and gray matter loss.
“In our findings, television viewing remained associated with cognitive function and gray matter volume after accounting for physical activity, suggesting that this sedentary behavior may impart a unique risk with regard to brain and cognitive health," Dougherty said.
He added, “This is an important finding since it is now well accepted that the neurobiology of dementia including brain atrophy begins during midlife. That’s a period where modifiable behaviors such as excessive television viewing can be targeted and reduced to promote healthy brain aging.”
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