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To investigate whether an association exists between long-term patterns of low physical activity and high television viewing time in early adulthood and cognitive decline in midlife, Kristine Yaffe, M.D. (pictured left), the Roy and Marie Scola Endowed Chair and Vice Chair of Research in Psychiatry at the University of California, San Francisco, and colleagues analyzed data of more than 3,200 individuals, aged 18 to 30. The physical activity and television viewing of the participants were assessed at three or more visits over 25 years. At year 25 of the study, the researchers assessed the participants’ memory, executive function, and processing speed. The investigation was a part of the Coronary Artery Risk Development in Young Adults study.
The researchers found that participants who reported low physical activity (less than 300 kcal/50 min session, three times per week) in more than two-thirds of the follow-up visits had significantly worse cognition in midlife than individuals reporting less frequent physical inactivity—even after adjusting for education, smoking habits, alcohol consumption, body mass index, and hypertension. Participants who reported regularly watching television for more than 4 hours per day throughout the study also had worse midlife cognition than those who reported less television viewing. Those who reported a history of long-term low physical activity and high television viewing were almost two times more likely to have poor cognitive function in midlife.
The researchers said that because global data suggests that levels of physical inactivity and sedentary behavior are increasing, understanding the relationship between physical activity in early adulthood and cognitive decline later in life may be of importance. They concluded that because research indicates that Alzheimer's disease and other dementias develop over several decades, increasing physical activity and reducing sedentary behavior beginning in early adulthood may have a significant public health impact.
An overview of the study by Yaffe is available here.
For more information about the role of physical activity in reducing the onset Alzheimer's disease or other dementias, see the Psychiatric News article "Exercise Found to Reduce Amyloid Plaques in Brain."