Adults with normal thinking and memory skills who have trouble sleeping may be at greater risk for Alzheimer’s disease, a new study shows. Researchers asked 101 older people with genetic risk factors for the degenerative brain disease to complete a sleep questionnaire. Samples of participants’ spinal fluid revealed those reporting poor sleep quality had more biological markers of Alzheimer’s, including buildups and tangles of toxic proteins, such as beta-amyloid and tau, as well as brain-cell damage and inflammation, the New York Times reports. “Not everyone with sleep problems is destined to develop Alzheimer’s disease,” says study author Barbara Bendlin of the University of Wisconsin. “We’re looking at groups of people, and over the whole group we find the association of poor sleep with the markers of Alzheimer’s.” The precise link is unclear. Previous studies suggest the brain “cleans house” overnight, clearing out harmful toxins, and sleep loss could disrupt this protective process.