Older adults who routinely sleep long hours carry higher blood levels of phosphorylated tau 181, a modified tau protein that is a hallmark of Alzheimer's disease, according to research from UT Health San Antonio published May 19 in Alzheimer's & Dementia, the Journal of the Alzheimer's Association. Drawing on 2,410 participants in the Framingham Heart Study, the team found that p-tau181 levels started climbing at sleep durations of about eight-and-a-half to nine hours a night and rose most sharply past 10 hours.
The relationship held after the researchers accounted for other health factors, and it persisted in a group whose average age was 70 and which was 55.2% female. What makes the finding useful is the biomarker itself: p-tau181 can now be measured in blood rather than only through spinal fluid or imaging, which opens the door to tracking neurodegenerative changes with a routine draw. The pattern the authors describe suggests that unusually long sleep may be a signal of early neurodegenerative processes rather than a benign habit.
First and corresponding author Vanessa M. Young, PhD, MS, a postdoctoral research fellow at the Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases, was direct about the study's limits. Because the data capture a single point in time, the work cannot show that long sleep causes Alzheimer's disease. Her takeaway was that the association may be worth monitoring, and that more sleep is not automatically better for the brain.
The work builds on a 2025 study by several of the same researchers, which tied sleeping nine or more hours a night to worse cognitive performance, an effect that was more pronounced among people with depression. The new analysis went further by adjusting for multiple health factors and pairing self-reported sleep duration with blood-based markers of Alzheimer's and neurodegeneration. Longitudinal follow-up would be needed to establish whether long sleep precedes the biological changes or reflects them.