“A lot of times, people think if they’re physically active, then they’re good,” says Marissa Gogniat, PhD, the study’s lead author and an assistant professor of neurology at the University of Pittsburgh. While decades of research have illustrated the health benefits of exercise, she says less is known about the impact of sitting, even when someone is active.
“Even though the people in the study were pretty physically active, their sitting was still accounting for more risk for Alzheimer’s,” Dr. Gogniat says.
Sedentary Time Led to Cognitive Decline Over the 7-Year Study
Researchers recruited about 400 adults who were 50 or older, and had each wear a watch measuring physical activity 24 hours a day for 10 consecutive days.
About 20 percent of participants had mild cognitive impairment at the beginning of the study, which can be a prequel to dementia. People were excluded if they had major medical conditions like heart failure, dementia, or psychiatric illness.
Then, over seven years, the researchers compared participants’ sedentary time (excluding sleep) to their cognitive performance and brain imagining.
The results showed that participants who spent more time sitting were more likely to have cognitive decline and brain degeneration, affecting memory and cognitive processing speed. These changes happened regardless of how much people exercised.
The cognitive and neurodegenerative changes were greater for participants who carried the APOE-e4 allele, which is a genetic risk factor for Alzheimer’s. Gogniat says routine blood work can tell if you carry this gene.
The researchers concluded that “sedentary behavior is an independent risk factor for Alzheimer’s disease.”
How Much Sitting Is Too Much?
The study participants were sitting about 13 hours per day on average. However, researchers didn’t quantify exactly how much time sitting may lead to cognitive decline.
Generally, there’s “not a magic number” for how much is too much sedentary time, says Carli Carnish, DPN, RN, an assistant professor at the Case Western Reserve University School of Nursing in Cleveland.
But the more you sit, she explains, the weaker your muscles often become, which makes it harder to be active. “I always tell my patients, ‘If you don’t move it, you lose it,’” Dr. Carnish says. This can quickly become a downward spiral for older adults, she says.
Older adults also may have mobility issues or physical limitations, says Constance Katsafanas, DO, a neurologist at the Marcus Neuroscience Institute, which belongs to Baptist Health South Florida in Boca Raton. “Some adults will need to spend more time sitting than others.”
The Study Has Some Limitations
Participants were recruited from the Vanderbilt Memory and Alzheimer’s Center in Nashville, Tennessee. Most were fairly active and and they had minimal health conditions. They were also more than 50 percent male and 85 percent white, non-Hispanic. Because of these factors, Gogniat says the results may not be generalizable to everyone.
Researchers also didn’t measure what participants were doing while sitting — for example, whether they were participating in mentally stimulating activities versus zoning out. Gogniat says her team is interested in examining that next.
“Logically, it would be easy to assume that doing things that stimulate you mentally are better for you than zoning out,” even while sitting, Dr. Katsafanas says.
How to Spend Less Time Sitting
To build more activity into your day, Carnish recommends starting with short bursts of movement every hour, even if it’s just a couple of minutes at a time. For example, walk in place or stretch during TV commercial breaks.
“A friend of mine walks on the treadmill while she watches TV at night,” Katsafanas says.
While it’s never too late to get active, it may not necessarily negate the effects of being sedentary, Katsafanas says. Good health as you age is a “multifaceted goal,” she adds, that includes moving more, sitting less, eating healthy, not smoking, and keeping your brain engaged.