Long-Term Tv Viewing Is Associated With Grey Matter Brain Volume In Midlife: The Coronary Artery Risk Development In Young Adults (Cardia) Study

Introduction: While it is generally accepted that a physically active lifestyle is important for overall health, sedentary behavior has become a public health focus due to evidence that it may impart unique risk for chronic diseases. The purpose of this study was to examine the association between 20-year television (TV) viewing patterns, as a proxy for sedentary behavior, with grey matter volume in midlife. We hypothesized that greater TV viewing in early to mid-adulthood would be associated with lower grey matter volume at midlife, independent from physical activity. Methods: We evaluated 599 participants (306 female, 264 black, mean age 30.3±3.5 at baseline and 50.2±3.5 years at follow-up and MRI) from the prospective CARDIA study. We assessed TV patterns with repeated interviewer-administered questionnaire spanning 20 years. Structural MRI (3T) measures of grey matter were assessed at year 20 during midlife. We used multivariable linear models to examine the association between long-term TV viewing (mean hours) and frontal cortex, entorhinal cortex, hippocampal, and total grey matter volumes, adjusting for demographics, intracranial volume, and study site. Results: Over the 20 years, participants reported viewing an average of 2.5±1.7 hours of TV per day (range: 0-10 hours). After multivariable adjustment, greater TV viewing was negatively associated with grey matter volume in the frontal (β= -0.773; p = 0.01) and entorhinal cortex (β= -23.8; p = 0.05) as well as total grey matter (β= -2.089; p = 0.003) but not hippocampus. These results remained unchanged after additional adjustment for physical activity. For each one standard deviation increase in TV viewing, the difference in grey matter volume z-score was approximately 0.06 less for each of the three regions ( p< 0.05; Figure 1). Conclusions: Among middle-aged adults, greater TV viewing in early to mid-adulthood was associated with lower grey matter volume. Sedentariness or other facets of TV viewing may be an important risk factor for brain aging even in middle age.