Consistently sleeping more than eight and a half hours per night could be an indicator of early brain changes associated with Alzheimer's disease, according to new research. The study, published in the journal Alzheimer's & Dementia, analyzed data from 2,410 participants in the Framingham Heart Study, with an average age of 70.
US-based researchers found that individuals who reported sleeping longer than 8.5 hours nightly had higher levels of p-tau181 in their blood. P-tau181 is a biomarker strongly linked to Alzheimer's disease, the most common form of dementia. The study also noted that levels of this biomarker increased more sharply in participants who slept more than 10 hours a night.
These findings persisted even after researchers accounted for factors such as age, sex, sleep apnea, and depression. The authors suggest that self-reported sleep durations of nine to ten hours or more per night might warrant further evaluation of both sleep patterns and cognitive health.
"We knew from the existing literature that the relationship between sleep and these biomarkers was unlikely to be simple, and that’s exactly what we found," said Dr. Vanessa Young, a postdoctoral research fellow at the Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases at UT Health San Antonio and the study's author.
Researchers emphasized that the findings do not imply that longer sleep causes Alzheimer's. Instead, they propose that extended sleep could be an early behavioral sign of underlying neurodegeneration. Further long-term studies are needed to fully understand the relationship between sleep duration and Alzheimer's disease.
The NHS recommends that adults aged 65 and under should aim for seven to nine hours of sleep per night, while those over 65 should target seven to eight hours. In the UK, approximately one million people live with dementia, affecting about one in 14 individuals over the age of 65. Dementia impacts language, reasoning, memory, and the ability to perform daily tasks.