Drowsiness during the day may indicate more significant issues than a poor night of sleep. The latest research published in Jama Neurology points to a correlation between Alzheimer’s and daytime sleepiness.

Studies show that people with Alzheimer’s disease typically experience disrupted sleep. However, it was unclear whether this disrupted sleep results from a buildup of amyloid plaque associated with Alzheimer’s, or vice versa.

To find an answer, Prashanthi Vemuri, an associate professor of radiology at the Mayo Clinic, and her colleagues jumped on board with the long-running Mayo Clinic Study of Aging, which assessed 3,000 older people recruited from Olmsted County, Minnesota. For this study, Vemuri picked 283 people of these 3,000 over the age of 70 who don’t have dementia. These participants described sleep habits and had several brain scans for amyloid over the course of seven years.

Of those examined, 22% reported daytime sleepiness at the start of the study. Vemuri found that these participants:

– Were more likely to display amyloid increases in their brains as the research progressed.

– Showed faster deposition of the protein than those who didn’t experience daytime sleepiness.

– Displayed heaviest amyloid buildups in regions of the brain associated with Alzheimer’s.

Despite these findings, the research doesn’t present a definitive answer of whether sleep problems lead to amyloid buildup, or if amyloid increases contribute to sleep disruptions. Further research is necessary to fully understand sleep habits and their influence on amyloid buildup. Studies also likely need to begin when people are younger.

Still, the new study tying Alzheimer’s and daytime sleepiness together reinforces the importance of good sleep to keep the brain healthy.

“I would hope that people understand that good sleep habits are important to have a healthy brain, since it can prevent amyloid, which is one of the primary proteins underlying Alzheimer’s disease,” Vemuri told Time.