Spending more time sitting could be bad for your brain health, a new study suggests.

The research found that older adults who spent more time sitting and lying down also had poorer cognitive function and shrinkage in parts of the brain tied to Alzheimer’s disease risk. This link between sedentary behavior and Alzheimer’s stood firm regardless of the participants’ exercise level.

The study was published in the journal Alzheimer’s & Dementia. Alzheimer’s disease, a progressive neurodegenerative disease that causes decreased memory and cognitive function, affects more than 7 million people in the U.S. alone. And cases are projected to hit 13 million by 2050. “This study is an important contribution to the growing body of evidence showing that how we move—or don’t move—throughout the day can meaningfully affect brain health,” said Prabha Siddarth, PhD, a research statistician at the Semel Institute for Neuroscience and Human Behavior at UCLA. “Sedentary behavior itself may be an independent risk factor for Alzheimer’s disease.”

Though there’s been plenty of research illustrating that more exercise lowers dementia risk, study author Marissa Gogniat, PhD, told Health she wanted to know whether people’s activity levels over the course of a whole day might impact their Alzheimer’s risk, too. So Gogniat, an assistant professor of neurology at the University of Pittsburgh and a former postdoctoral fellow at the Vanderbilt Memory and Alzheimer’s Center, studied a group of 404 older adults to find out.

Study participants wore a smartwatch that recorded their activity levels for one week, and had various neuropsychological assessments and brain MRIs over a seven-year period. On average, participants spent about 13 hours sitting or lying down throughout the day. Results showed that, regardless of exercise level, people who spent more time sitting and lying down had: Worse episodic memory; Lower scores on various cognitive performance tests; Greater declines in volume in certain areas of the brain; Smaller Alzheimer’s neuroimaging signature, which is linked to a greater risk of cognitive decline in the future.

The association between sedentary behavior and Alzheimer’s risk was even more significant for those who had a genetic risk factor for the disease, called the APOE-ε4 allele. This research “fills a critical gap” in how we understand movement and risk for cognitive decline, Siddarth explained, and further builds on the idea that lifestyle behaviors can impact how the brain functions.