Sleeping longer than 8.5 hours a night may be a sign of Alzheimer's

• Both sleep disturbance and excess sleep have been linked to development of dementias, particularly Alzheimer’s disease.
• Now, a study has found that people with particularly long sleep duration are more likely to have more of a brain protein linked to Alzheimer’s.
• The study found that sleeping for more than 8.5 hours a night was associated with blood biomarkers of tau protein, suggesting that long sleep may indicate early neurodegeneration.

The earlier dementia — of which Alzheimer’s disease is the most common — is detected, the better the prognosis for the person diagnosed.

Although there is no cure, early diagnosis of Alzheimer’s can help to delay the progression of the disease, allow the use of disease-modifying treatments, such as lecanemab and donanemab where appropriate, and give patients and carers time to arrange appropriate care.

Several studies have linked sleep changes to the development of Alzheimer’s disease, and now a study has suggested a possible physiological mechanism underlying the link.

The new study, published in Alzheimer’s and Dementia, the journal of the Alzheimer’s Association, found that people who slept for an average of more than 8.5 hours a night had higher levels of the blood biomarker p-tau181, suggesting that long sleep may be an early sign of neurodegenerative changes.

Steven Allder, MD, a consultant neurologist at Re:Cognition Health, who was not involved in the study, told Medical News Today:

“This study strengthens growing evidence that changes in sleep may be linked to the earliest biological processes involved in Alzheimer’s disease, rather than simply being a consequence of aging. […] What is particularly interesting here is the association between longer sleep and higher levels of plasma phosphorylated tau (p-tau181), a biomarker that reflects Alzheimer’s pathology.”