Alzheimer’s: Sleeping More Than 8.5 Hours May Be an Early Sign of the Disease, According to a Study

A new study published in Alzheimer’s & Dementia establishes a link between prolonged sleep duration and higher levels of P-tau181, a blood biomarker associated with Alzheimer’s disease. While the research does not demonstrate a cause-and-effect relationship, it suggests that unusually long sleep could be considered a potential warning sign, particularly among older adults

• A study associates sleeping more than 8.5 hours per night with higher levels of P-tau181, a biomarker linked to Alzheimer’s disease.
• Researchers analyzed data from 2,410 adults with an average age of 70.
• P-tau181 levels gradually increased among people sleeping more than 8.5 hours, with a stronger rise after 10 hours of sleep.
• The authors emphasize that the study does not prove that long sleep causes Alzheimer’s disease.
• Prolonged sleep could represent an early indicator of the disease and may warrant discussion with a doctor if it becomes a regular pattern.

Long sleep duration: a possible early marker of Alzheimer’s disease

Is sleeping for a long time necessarily beneficial? This is the question raised by a study published on May 19, 2026, in the scientific journal Alzheimer’s & Dementia. Researchers identified an association between prolonged sleep duration and higher levels of P-tau181, a modified form of the tau protein that can now be detected through a simple blood test and is considered a biomarker of Alzheimer’s disease.

To reach this conclusion, the research team analyzed data from 2,410 individuals with an average age of 70. Participants reported their sleeping habits through questionnaires, while blood tests were used to measure several biomarkers associated with neurodegenerative diseases. The authors found that P-tau181 levels began to increase among people who slept more than 8.5 hours per night, with a particularly significant rise among those sleeping more than 10 hours. However, associations with other biomarkers disappeared after accounting for kidney function. The researchers therefore suggest that prolonged sleep may represent a potential behavioral marker of elevated P-tau181 levels.

An association that does not prove a cause-and-effect relationship

The researchers nevertheless urge caution when interpreting these findings. Vanessa M. Young, the study’s lead author, explains that this was an observational study conducted at a single point in time. Therefore, it is impossible to conclude that sleeping for long periods causes Alzheimer’s disease. However, the findings suggest that longer sleep duration is not necessarily always a sign of better brain health and should be taken into consideration.

The research team proposes another possible explanation: prolonged sleep may be a consequence of early brain changes associated with the disease. The researchers explain that tau protein begins accumulating early in certain areas of the brainstem involved in regulating sleep and wakefulness. Damage in these regions could therefore contribute to longer sleep duration several years before the appearance of the first cognitive symptoms. From this perspective, excessive sleep would be considered more of an early warning signal rather than a triggering factor.

Finally, the authors recommend that people who regularly sleep between nine and ten hours per night, or even longer, discuss it with their doctor. Vanessa M. Young believes that this can provide an opportunity for a useful conversation about sleep quality and overall brain health. However, the researchers emphasize that their findings must be confirmed by long-term studies before prolonged sleep can be considered a reliable tool for assessing Alzheimer’s disease risk.