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Watching TV increases risk of dementia in seniors

A new study led by the University of Southern California (USC) and the University of Arizona has found that adults aged 60 or older who sit for long periods of time watching TV or engaging in other such passive, sedentary behaviors are at increased risk of developing dementia. Surprisingly, the investigation revealed that other sedentary activities, such as using a computer or reading, were not associated with similar risks.

“It isn’t the time spent sitting, per se, but the type of sedentary activity performed during leisure time that impacts dementia risk,” said study lead author David Raichlen, a professor of Biological Sciences and Anthropology at USC. 

“We know from past studies that watching TV involves low levels of muscle activity and energy use compared with using a computer or reading. And while research has shown that uninterrupted sitting for long periods is linked with reduced blood flow in the brain, the relatively greater intellectual stimulation that occurs during computer use may counteract the negative effects of sitting.”

To investigate potential correlations between sedentary leisure activities and dementia in older adults, the scientists used self-reported data from the U.K. Biobank involving over 145,000 participants aged 60 or older who were not diagnosed with dementia at the beginning of the study. After 12 years of follow-up, the researchers used hospital inpatient records to determine new dementia diagnoses, and found 3,507 cases from their cohort.

Surprisingly, even in individuals who were highly physically active, time spent watching TV was associated with increased risk of dementia, while leisure-time spent using a computer was linked to a reduced risk for dementia. “Although we know that physical activity is good for our brain health, many of us think that if we are just more physically active during the day, we can counter the negative effects of time spent sitting,” said study senior author Gene Alexander, a professor of Psychology at the University of Arizona.

“Our findings suggest that the brain impacts of sitting during our leisure activities are really separate from how physically active we are, and that being more mentally active, like when using computers, may be a key way to help counter the increased risk of dementia related to more passive sedentary behaviors, like watching TV.”

“What we do while we’re sitting matters. This knowledge is critical when it comes to designing targeted public health interventions aimed at reducing the risk of neurodegenerative disease from sedentary activities through positive behavior change,” Professor Raichlen concluded.

The study is published in the journal Proceedings of the National Academy of Sciences.

By Andrei Ionescu, Staff Writer  

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