senior man watching tv

You may want to think twice before grabbing that remote. A new study finds that adults 60 and older who sit for long stretches watching TV or are passively sedentary in other ways are at increased risk of developing dementia. 

“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 University of Southern California’s Dornsife College of Letters, Arts and Sciences.

The study, which was published this week in the Proceedings of the National Academy of Sciences, found that the risk is lower for those who are active while sitting, such as reading or using computers. 

“We know from past studies that watching TV involves low levels of muscle activity and energy use compared with using a computer or reading,” Raichlen said. “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 from USC and the University of Arizona used self-reported data from the U.K. Biobank, a large-scale biomedical database of more than 500,000 participants across the United Kingdom, to investigate possible correlations between sedentary leisure activity and dementia in older adults. More than 145,000 participants aged 60 and older — all of whom did not have a diagnosis of dementia at the start of the project — completed questionnaires about their levels of sedentary behavior during the 2006-2010 baseline examination period. After an average of nearly 12 years of follow-up, the researchers used hospital inpatient records to determine dementia diagnosis. They found 3,507 positive cases. The team then adjusted for certain demographics and lifestyle characteristics that could affect brain health.

Perhaps most striking was the finding that results remained the same even among participants who were 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 the brain disease.