Long sleep may signal early Alzheimer's changes, not cause disease: study

Sleeping excessively long hours, particularly 9 to 10 hours per night, might not be a cause of Alzheimer's disease but could signal early brain changes associated with the condition, a recent study suggests. Researchers have identified a potential link between extended sleep durations and elevated levels of a key Alzheimer's biomarker.

The study, published in the journal 'Alzheimer's & Dementia,' analyzed blood biomarkers from 2,410 participants in the Framingham Heart Study, with an average age of 70. The research focused on the relationship between sleep duration and phosphorylated tau 181 (p-tau181), a modified form of the tau protein that is a hallmark of Alzheimer's pathology and can be detected through blood tests.

Findings indicated that blood p-tau181 levels began to rise gradually after 8 hours and 30 minutes of sleep, with a steeper increase observed beyond 10 hours. This non-linear relationship suggests that the risk doesn't increase steadily but accelerates after a certain threshold. The lowest p-tau181 levels were found in individuals sleeping 7 to 8 hours, aligning with established recommendations for adult sleep duration.

Dr. Vanessa V. van der Walt, the study's lead author, commented, "From a brain health perspective, sleeping more is not necessarily better." She added, "Long sleep may be a signal that warrants careful attention regarding brain changes." The association remained significant even after accounting for factors like age, sex, sleep apnea, depression, kidney function, and APOE ε4 genotype.

While the study points to a potential connection between long sleep and Alzheimer's pathology, researchers emphasize that further investigation is needed to confirm this link. They theorize that damage to specific brain regions regulating sleep could lead to prolonged sleep before cognitive decline becomes apparent. Alternatively, self-reported sleep times might reflect time spent in bed rather than actual sleep, with frequent awakenings leading individuals to stay in bed longer to compensate. Deep sleep is crucial for clearing brain waste, and fragmented sleep, even if lengthy, may be less effective. The study did not measure sleep quality, leaving the exact mechanisms unclear. Nevertheless, the researchers advise that anyone experiencing a noticeable increase in sleep duration or consistently sleeping more than 9-10 hours without a clear reason should consult a doctor about potential sleep disorders and overall brain health.

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From a brain health perspective, sleeping more is not necessarily better. Long sleep may be a signal that warrants careful attention regarding brain changes.