Alzheimer's disease linked to long sleep duration in older adults

Getting plenty of sleep is often seen as healthy, but new research suggests that regularly sleeping for unusually long stretches may indicate trouble for your brain.

A team at UT Health San Antonio has found that older adults who typically sleep more than eight and a half hours a night show higher levels of a blood protein tied to Alzheimer’s disease, according to findings published in Alzheimer’s & Dementia.

Scientists analyzed data from 2,410 participants in the long-running Framingham Heart Study. The volunteers had an average age of 70, and just over half were women. The research team compared their usual sleep duration with several blood markers related to brain health and neurodegenerative disease.

One marker stood out: phosphorylated tau 181, or p-tau181. This protein tends to accumulate inside brain cells in Alzheimer’s disease, and new blood tests now make it possible to track these changes simply.

The results showed that people who usually slept between eight and a half and nine hours had higher p-tau181 levels than those who slept less. The difference was even more pronounced among those sleeping ten hours or more each night.

This pattern held even after the team adjusted for age, sex, depression, sleep apnea, and genetic risk.

The researchers caution that their findings do not prove that sleeping longer directly causes Alzheimer’s. Since the study only looked at people at a single point in time, it is possible that needing more sleep is an early warning sign that changes in the brain are already underway, even before memory loss appears.

Earlier studies have linked both too little and too much sleep to dementia risk, but this team used advanced methods to spot a non-linear pattern. The risk marker increased mainly when sleep exceeded eight and a half hours.

There’s no reason to worry if you sometimes sleep longer because of illness or stress. But if you regularly find yourself needing nine to ten hours of sleep each night without an obvious cause, it may be worth talking with your doctor to help safeguard your brain health as you age.