High TV Viewing, Low Activity Linked to Poorer Cognition

Pam Harrison

December 03, 2015

Watching television for 3 hours or more a day in young adulthood, coupled with low levels of physical activity, may lead to poorer cognitive function in midlife, the first study of its kind suggests.

Lead author Tina Hoang, MSPH, Northern California Institute for Research and Education, San Francisco, and senior author Kristine Yaffe, MD, University of California, San Francisco, found that young adults aged approximately 25 years who watched television for 3 hours or more a day demonstrated poorer performance on several measures of executive function and processing speed 25 years later compared with those watching less.

When coupled with low levels of physical activity, watching a lot of television in young adulthood almost doubled the risk of performing poorly on the same measures of cognitive function in midlife.

"Our results indicate that the lifestyle behaviors in early adulthood that were evaluated in this study could have an effect on the risk of cognitive impairment in midlife," Hoang and colleagues observe.

"And they support a potential role for both physical activity and sedentary behavior as modifiable risk factors for prevention."

The study was published online December 2 in JAMA Psychiatry.

Young adults aged 18 to 30 years were recruited from population-based samples of four US cities and were subsequently enrolled in the Coronary Artery Risk Development in Young Adults (CARDIA) study.

The study was carried out from 1985 to 2011. Follow-up examinations were performed every 2 to 5 years over a 25-year period.

Of 5115 persons who were enrolled in the study, 3499 completed the last visit at year 25. The current analysis included 3247 participants.

At baseline and at each follow-up visit, physical activity was measured using the Physical Activity History Questionnaire. On the basis of duration of participation as well as intensity of exercise, a total activity score was calculated.

At years 5, 10, 15, 20, and 25, participants were asked how many hours a day, on average, they spent watching television. A pattern of high television viewing over 25 years was defined as activity levels within the top quartile of year 5 ― namely, 3 hours a day or more during two thirds of the visits.

At year 25, interviewers administered three cognitive tests: the Digit Symbol Substitution Test (DSST), which assesses processing speed and executive function; the Stroop test, which assesses executive function; and the Rey Auditory Verbal Learning Test (RAVLT), which assesses verbal memory.

Compared with participants with moderate to high long-term patterns of physical activity, young adults with low levels of physical activity were 47% more likely to do poorly on the DSST (adjusted odds ratio [aOR], 1.47; 95% confidence interval [CI], 1.14 - 1.90).

A total of 353 participants, or approximately 11% of the cohort, met the criteria for a long-term pattern of high television viewing.

"This high level [of television viewing] was associated with poor cognitive performance at year 25 on all cognitive tests," Hoang and colleagues report.

After multivariate analysis, performance on the DSST and the Stroop test was poorer among those who watched the most television. No significant association was found regarding scores on the RAVLT test after adjustment for age, race, sex, educational level, smoking, alcohol use, body mass index, and hypertension.

Table. Cognitive Function Evaluation by TV Viewing Pattern

Test Poor Cognitive Performance (%) aOR (95% CI)
DSST  
Low to moderate TV viewing 14.3 1.64 (1.21 - 2.23)
High TV viewing 27.4  
Stroop test  
Low to moderate TV viewing 12 1.56 (1.13 - 2.14)
High TV viewing 21.4  
RAVLT  
Low to moderate TV viewing 19.1 1.14
High TV viewing 27.1  

 

Most Active Patterns

When physical activity patterns and television viewing time were combined, approximately three quarters of the cohort were found to have moderate to high physical activity levels and low to moderate levels of television viewing.

In contrast, only about 3% of the cohort were found to have the lowest levels of physical activity and high levels of television viewing.

In adjusted models, those with the least active patterns of physical activity and high levels of television viewing were almost twice as likely to perform poorly on the DSST (aOR, 1.95; 95% CI, 1.19 - 3.22) and on the STROOP tests (aOR, 2.20; 95% CI, 1.36 - 3.56) compared with those who were the most active and watched the least television.

Passive Experience

Asked by Medscape Medical News how high levels of television viewing might lead to poorer cognitive performance in midlife, Hoang felt it might be that watching television is a passive experience and is thus less cognitively engaging.

"However, there could be a number of other pathways linking TV watching to physical activity," she said.

"TV watching has been linked to increased cardiovascular risk factors but also to other behavioral patterns, including social inactivity and poor diet," she noted.

"Most people don't really think about their brain health until later in life, but these findings are telling us that an active lifestyle is important for keeping your brain healthy, even for young and middle-aged adults."

Commenting on the study, Kathryn Papp, PhD, instructor of neurology at Brigham and Women's Hospital, Boston, Massachusetts, told Medscape Medical News that this large study provides concrete data showing that how we live affects how we think.

"It also provides further evidence to the growing consensus that there is a link between lifestyle factors and cognitive aging," Dr Papp said.

It is particularly interesting, she added, that researchers found a relationship between television viewing and worse performance on tests that require executive function, such as processing speed and attention, but not on tests of memory.

"This may mean that television viewing may have more of an impact on one aspect of cognition over another," she said, adding, however, that because this is an observational study, "we cannot conclude that television watching and physical inactivity cause worse cognitive functioning later in life but rather that there is a relationship there that is important to explore further."

The CARDIA study is supported by the National Heart, Lung, and Blood Institute (NHLBI) in collaboration with the University of Alabama at Birmingham, Northwestern University, University of Minnesota, the Kaiser Foundation Research Institute, and Johns Hopkins University School of Medicine. CARDIA is also partially supported by the Intramural Research Program of the National Institute on Aging (NIA) and through an intra-agency agreement between the NIA and the NHLBI. Tina Hoang has disclosed no relevant financial relationships. Dr Yaffe serves on the data safety and monitoring board for Takeda.

JAMA Psychiatry. Published online December 2, 2015. Abstract

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