There’s an old saying which warns that “television will rot your brain.” Several new studies find it might be true. Researchers find that watching more TV each day throughout adulthood and middle age can age the brain faster and put viewers at greater risk for cognitive decline later in life.

Study authors also discovered moderate-to-high TV viewing during midlife also has a connection to lower grey matter volumes. However, sedentary behaviors which stimulate the brain such as reading did not have the same negative effects.

Grey matter is the darker tissue of the brain and spinal cord. It helps to coordinate muscle control, seeing, hearing, decision-making, and other important brain functions. The higher a person’s volume of brain grey matter, the better cognitive skills they typically have.

Researchers presented their findings in a series of studies at the American Heart Association’s Epidemiology, Prevention, Lifestyle & Cardiometabolic Health Conference 2021.

TV speeds up the mental aging process

One study from Johns Hopkins Bloomberg School of Public Health specifically looked at TV’s impact on grey matter volumes. Dr. Ryan Dougherty and his team in the department of epidemiology examined 599 people with an average age of 30, asking them about the average number of hours per day they had spent watching television over the previous year.

The group then underwent MRI scans which revealed those reporting the highest amounts of TV time had the lowest grey matter volumes. The study also discovered that grey matter volume was declining by 0.5 percent for every additional hour of TV viewed. That’s the same as the annual rate of decline in people during middle age.

“In the context of cognitive and brain health, not all sedentary behaviors are equal,” Dr. Dougherty says in a media release. “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.”

“Considering the contextual differences in varying sedentary behaviors is critical when investigating cognitive and brain health,” the lead author adds.

“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 respect to brain and cognitive health. 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.”

Dementia is rapidly spreading across the world

Scientists from New York and Alabama looked at different data, focusing on cognitive decline, the risk of dementia, and structural brain markers from brain imaging scans. Worldwide, doctors diagnose around 10 million new dementia cases annually, according to the World Health Organization. By 2050, researchers expect the prevalence of dementia to increase by 116 percent in high-income countries and 264 percent in low-income countries.

“There are currently no medications available to cure or stop dementia,” notes Priya Palta, a neurologist at New York-Presbyterian/Columbia University Irving Medical Center. “However, a recent report showed that nearly 40% of worldwide dementia diagnoses may be prevented or delayed by modifying twelve risk factors including exercise.”

“Our findings suggest that the amount of television viewing, a type of sedentary behavior, may be related to cognitive decline and imaging markers of brain health,” Palta adds. “Therefore, reducing sedentary behaviors, such as television viewing, may be an important lifestyle modification target to support optimal brain health.”

In this study, Palta’s team asked participants how much they watched television during their leisure time. However, the group did not base their answers on specific hours or amounts of time. Instead, they reported whether they never or seldom watched TV (low), sometimes watched TV (medium/moderate), or often watched TV (high).

The data included results from 10,700 adults with an average age of 59. Researchers visited these individuals five times over a 24-year span to conduct follow-up cognitive tests, focusing on working memory, language, and executive function and processing speed.

Over 15 years, those who reported watching high amounts of television had a 6.9 percent greater cognitive decline that those who hardly used their TV. However, high amounts of television viewing did not have a strong connection to higher dementia risk.

Sedentary lifestyles can be especially bad for seniors

Meanwhile, the Birmingham researchers looked at 1,601 adults from the same data set, with an average age of 76.2 who underwent MRI brain scans. Of these patients, 971 had rated their TV viewing as high in the earlier visits. Those who described their TV viewing as moderate or high had lower volumes of grey matter more than a decade later in life; which indicates greater brain atrophy or deterioration. Study authors note the association between the level of TV watching and brain grey matter was greater with persistent television viewing throughout midlife.

“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,” says Kelley Pettee Gabriel, professor of epidemiology at the University of Alabama at Birmingham.

“This is important to look at because other studies have shown that physical activity and sedentary behaviors may have different effects on health and disease. Engaging in healthy behaviors during midlife, between ages 45 to 64 years in the context of our study, may be important factors to support a healthy brain later in life.”

Could other forms of inactivity be damaging the brain too?

Researchers in all of these studies note their findings have limitations since they rely on self-reporting by the participants. Also, television viewing is only one type of sedentary behavior and provides an incomplete picture of total sedentary time.

“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 Elkind says.

“These are interesting correlations among television viewing, cognitive decline and brain structure.

Television viewing 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.”
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