While we know a sedentary lifestyle can be dangerous to health, few studies have actually examined the effects. Research carried out over 25 years by California's Institute for Research and Education has recently shown the dangers of television for our neurons, even in those who exercise regularly. According to T. D. Hoang and his team, regular television watching causes a decline in cognitive ability. How did the scientists come to this alarming conclusion?

In this study, the exercise and TV-watching habits of 3,247 adults (54.5% women) between the ages of 18 and 30 (average age: 25.1) were collected and analyzed over the course of 25 years (from March 25, 1985 through August, 31 2011). At the beginning of the study, among participants enrolled in the CARDIA study (Coronary Artery Risk Development in Young Adult), 92.9% had completed at least high school. Each person filled out the initial questionnaire and was contacted again every two to five years to reply to another questionnaire. The participants were divided into two groups according to their television habits: frequent viewers (more than 3 hours of television per day) and moderate viewers (less than 3 hours per day). Their cognitive function was evaluated using the DSST (Digit Symbol Substitution Test), Stroop test, and RAVLT (Rey Auditory Verbal Learning Test).

The results and analyses (carried out between June 2014 and April 2015) showed that the most frequent viewers over the 25 years (10.9%) were more likely to perform poorly on the cognitive tests. Secondly, the participants with low physical activity (16.3%) performed poorly on the DSST. Thirdly, when compared to moderate viewers engaging in regular physical activity, frequent viewers who exercised little were nearly twice as likely to perform poorly on cognitive tests. Too much television and a lack of physical activity represent independent factors linked to cognitive decline.

Exercise can’t compensate for the harmful effects of too many hours spent watching television. If you’re athletic, you are undoubtedly maintaining your cognitive abilities better than sedentary individuals, but if you also watch television for more than three hours per day, it is likely to have negative consequences on your intellectual activity.

According to Michel Desmurget (Research Director at INSERM's Center for Cognitive Neuroscience in Lyon), several causes may be at work in the decline of cognitive function, including: lack of stimulation (TV programs that are intellectually unstimulating), inducement of chronic anxiety (stressful programs), decrease in the quality and quantity of sleep, and stimulation of alcohol and tobacco consumption.

As this study goes to show, exercise can’t protect you from excessive television watching! Protecting your neurons doesn't just require exercise, but also letting go of the remote control!