Scientists say one everyday habit may be quietly shrinking your brain

Winding down looks different for everyone, but it often involves some sort of sitting—it might be sitting back to read a novel or lounging while watching one’s favorite show. But a new study suggests that, despite it being a similar physical task, “not all sitting is created equal.”

A recent study published in The Journal of the Alzheimer’s Association found doing mentally engaging tasks while sitting is better for the long-term health of the brain than watching TV. The study analyzed data from the Atherosclerosis Risk in Communities (ARIC) study, a historic long-running study that explores risk factors related to cardiovascular and brain health. Researchers found that adults who watched TV “very often” would see significant structural changes, with tissue loss seen in areas related to vision, logic, and memory.

“We frequently encourage the public not to spend too much time sitting down, but experts may want to expand that recommendation to encompass the activities done while sitting, since those seem to have distinct impacts on brain health,” the study’s author, Natan Feter, told Neuroscience News.

The study looks at data from participants enrolled between 1987 and 1989 for the ARIC study, whose roughly 1700 adult participants averaged 53 years old. Among the various questions participants have responded to include their TV-watching habits as well as how long they spent sitting at work.

Through MRI imaging, researchers found that participants with heavy TV-watching habits had structural differences associated with cognitive decline and dementia, as well as changes related to the occipital and frontal lobes, which govern executive functioning and visual processing.

While the results account for controlled factors—like alcohol use and body mass index—the study did not take a baseline MRI, so exact individual structural changes are not quantifiable, although future studies with a baseline might provide further insights.

The contrasting results from sitting while doing mentally engaging activities versus watching TV relates to how the brain behaves during the activities. For instance, when performing tasks related to work that require writing, problem solving, planning, or memory retrieval, the electrical firings needed to complete the tasks work as a kind of workout for the brain. Conversely, watching TV is more of a passive activity, requiring less activity from the brain, eventually leading to structural changes after years of decreased cognitive demand.