Study links frequent TV watching to brain changes later in life

Natan Feter of the University of Southern California's Dornsife College of Letters, Arts and Sciences on the impact of sedentary activity on brain health.

Spending hours in front of the television could be linked to changes in the brain later in life, according to a new study.

Researchers followed more than 1,700 adults who were about 53 years old on average when they reported how often they watched television. More than 20 years later, brain scans found those who watched TV most often were more likely to have brain changes associated with cognitive decline and dementia.

But the researchers say it isn’t simply sitting and watching an excessive amount of TV that’s linked to brain health. Instead, the study suggests the type of sedentary activity may matter.

“The main finding here is that not all sitting is equal in terms of, not effects, but how sitting is associated with brain health and brain structure and cerebrovascular damage,” said corresponding author Natan Feter, a postdoctoral scholar in the Human and Evolutionary Biology program at the University of Southern California’s Dornsife College of Letters, Arts and Sciences, in an interview with CTVNews.ca.

“We spend most of our day in sedentary behaviour. Sitting is the most common form of sedentary behaviour. We spend 50 per cent of our waking time sitting, basically,” he said. ”We saw that where this sitting is occurring, the context in which this scene is occurring, has an impact on how sedentary behaviour affects our brain.”

The study, published this month in Alzheimer’s & Dementia, analyzed data from participants in the long-running Atherosclerosis Risk in Communities (ARIC) study in the United States.

Participants were asked how often they watched television during their free time and how much of their workday they spent sitting. More than two decades later, they underwent MRI brain scans.

Compared with people who rarely watched television, those who watched it most often had more white matter hyperintensities, which are changes in the brain linked to aging, stroke risk, cognitive decline and dementia. They also had smaller volume in parts of the brain involved in memory, thinking and visual processing, including regions vulnerable to Alzheimer’s disease.

The associations remained after researchers accounted for physical activity, suggesting the findings could not be explained by exercise levels alone.

The study found people who spent more time sitting at work had lower levels of white matter hyperintensities and larger volume in some brain regions, suggesting work-related sitting may have different associations with brain health than television viewing.

Researchers also found the associations between television viewing and brain structure were stronger in men than in women.

“Usually, women spend more time sitting during watching TV and this time is more interrupted for household activities, household demands. Men usually spend more time in uninterrupted seating,” Feter explained. “We also know that there are biological differences between women and men that might explain this sex-dependent association.”

Feter said today’s viewing habits may be even more concerning than when the data were collected in the late ’80s, because people often divide their attention between multiple screens.

“I think the way we watch TV today is even more dangerous than before, because we are trying to focus on so many different things,” he said. “I think this impaired attention process might have some … modifier role in the association that we see between sedentary behaviour and brain health."

The study was observational, meaning it cannot show that watching television caused the brain changes. It also relied on participants reporting their own television viewing and workplace sitting habits, and researchers did not have brain scans from the beginning of the study to compare changes over time.