People aged 60+ who sit watching TV for long periods at increased risk of dementia

Those aged 60 and over who sit for long periods of time doing a passive activity, such as watching TV, may be increasing their risk of developing dementia.

Researchers from the University of Southern California and University of Arizona found “what we do while we’re sitting matters” as passive activities such as watching TV increase your risk of dementia more than if you are reading or using a computer.

“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 author David Raichlen, professor of biological sciences and anthropology at the USC Dornsife College of Letters, Arts and Sciences.

“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.”

Researchers used self-reported data from the UK Biobank, a large-scale biomedical database of more than 500,000 people in the UK, to look at possible correlations between sedentary leisure activity and dementia in older adults.

More than 145,000 participants aged 60 and older, none of them having a diagnosis of dementia at the start of the project used touchscreen questionnaires to self-report information about their levels of sedentary behaviour during the years 2006-2010.

After an average of nearly 12 years of follow-up, the researchers used hospital inpatient records to determine dementia diagnosis and found 3,507 positive cases. Then, the team adjusted for certain demographics such as age and sex and lifestyle characteristics like smoking and alcohol use.

They found even in people who are highly physically active, time spent watching TV was associated with increased risk of dementia, and leisure time spent using a computer was associated with a reduced risk of developing 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 author Gene Alexander, professor of psychology at the Evelyn F. McKnight Brain Institute 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 behaviours, like watching TV.”

Knowing how sedentary activities impact human health could lead to some improvements.

“What we do while we’re sitting matters,” David Raichlen added. “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 behaviour change.”

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