How much sitting increases the risk of dementia?
Older adults who sit a lot may have a greater risk of developing dementia. And that’s true even if they also get a decent amount of exercise.
Research from the University of Southern California and the University of Arizona found that adults 60 and older who spend more than 10 hours a day sitting — whether at work or watching TV or even while driving — have a significantly increased risk compared to others.
The study is published in JAMA, the Journal of the American Medical Association.
The researchers say that the at-risk group includes most older Americans. And the total sedentary time accumulated over the day is what matters. In a news release on the study, the researchers called their findings “notable ... considering the average American is sedentary for about 9.5 hours each day.”
As The Washington Post reported, “The negative effects of extended sitting can be so strong, researchers found, that even people who exercise regularly face higher risk if they sit for much of the day.”
“Many of us are familiar with the common advice to break up long periods of sitting by getting up every 30 minutes or so to stand or walk around,” said David Raichlen, study author and professor of biological sciences and anthropology at USC, quoted in the release. “We wanted to see if those types of patterns are associated with dementia risk. We found that once you take into account the total time spent sedentary, the length of individual sedentary periods didn’t really matter.”
About the study
Data for the study came from the U.K. Biobank, which is a big biomedical databank of information collected across the United Kingdom. As part of a biobank sub-study, 100,000 adults wore sophisticated activity trackers on their wrists around the clock for a week to measure movement. The study focused on those in the sub-study who were 60 or older and had not been diagnosed with dementia when they entered the study — about 50,000 individuals.
The data was analyzed and categorized by the intensity of activity. The sedentary behavior excluded time spent sleeping.
“After an average of six years of follow-up,” the release said, “the researchers used inpatient hospital records and death registry data to determine dementia diagnosis. They found 414 cases positive for dementia.”
Related
Then they adjusted for demographic and lifestyle factors that could make a difference in terms of brain health, including age, sex, education level, race/ethnicity, chronic conditions, genetics, diet, smoking, physical activity, self-reported mental health and alcohol use.
“We were surprised to find that the risk of dementia begins to rapidly increase after 10 hours spent sedentary each day, regardless of how the sedentary time was accumulated,” said Gene Alexander, another study author and professor of psychology and psychiatry at the University of Arizona and Arizona Alzheimer’s Disease Research Center.
“Importantly, lower levels of sedentary behavior, up to around 10 hours, were not associated with increased risk,” he added.
Raichlen said that should be comforting to people who have office jobs that require sitting for a long time, “as long as we limit our total daily time spent sedentary.”
The researchers said more study is needed to establish a causal relationship between sitting 10 hours or more and dementia. Research is also needed to see to what degree, if any, physical activity can lower that risk.
Other risks of sitting too much
The Post article notes that most people know the “downsides of over-sitting,” including increased risk of heart disease, obesity, diabetes and even premature death, when compared to those who get up often and are regularly physically active.
A separate article from The Washington Post notes that even working out for a half-hour a day “might not be enough” to make the health issues created by time spent sitting go away.
Other research does offer a bit of encouragement. A study in PNAS, which also used data from the U.K. Biobank, found some differences between cognitively passive activity while sitting, such as watching TV, and seated tasks that were mentally engaging.
As Medical News Today summarized those findings, “Being mentally active and engaged while sitting may reduce the chances of developing dementia. Conversely, sitting passively increases this risk.”
Clear through numerous studies, though, is that avoiding too much sitting is better for your brain health. Couch potatoes may set themselves up for neurocognitive decline.
