Frequent TV viewing in middle age is associated with a decrease in brain structure volume

The study included about 1,700 adults with an average age of 53, who answered questions about their leisure time and workday in 1987-1989, including how often they watched TV (on a scale from “never/rarely” to “very often”) and how much time they spent sitting at work. More than 20 years later, these same individuals underwent brain MRI scans.

The results showed that those who watched TV “very often” had:

• a smaller volume of brain regions where early signs of Alzheimer’s disease often appear;
• a larger volume of white matter hyperintensities, a marker of small-vessel brain damage associated with cognitive decline and dementia;
• a reduction in the frontal lobe (responsible for executive functions) and the occipital lobe (responsible for processing visual information).

It is important to note that these differences persisted even after taking into account a variety of factors, including physical activity levels, diabetes, body mass index, smoking, and alcohol consumption.

It is particularly noteworthy that the findings suggest that sitting is not the only factor at play. The researchers conducted a separate comparison between TV viewing and sedentary work, revealing an unexpected contrast. Individuals who engaged in sedentary work had larger frontal and occipital lobe volumes and lower white matter hyperintensities, indicating healthier brain functioning. The authors suggest that the reason may be cognitive load, as many sedentary professions require mental stress, which probably has a protective effect.

When analyzed separately by gender, it turned out that the main changes in the brain (both related to TV viewing and to working sitting) were more pronounced in men.

The study has limitations: data on TV viewing time is based on self-assessment of the participants, and the initial brain scans were not taken, so it is not possible to directly trace the dynamics of changes in each person. Nevertheless, the work provides important grounds for a more nuanced formulation of lifestyle recommendations.

According to the authors, current health advice often boils down to “sit less, move more.” However, the new data suggests that not all sedentary behaviors are equal, and it matters what a person does while sitting. In the future, recommendations may become more differentiated. For example, instead of simply reducing sitting time, it may be more effective to focus on reducing TV viewing and replacing it with cognitively demanding activities.