Scientists used a computer program that looks at brain waves while people sleep. The program guesses a person’s “brain age.” If the brain looks older than the person’s real age, the chance of dementia goes up.
For every ten years the brain age is higher than the actual age, the risk of dementia rises by about 40 %. When the brain age is younger than the real age, the risk is lower.
The study examined data from roughly 7,000 volunteers aged 40 to 94. None had dementia at the start. Over 3‑to‑17 years of follow‑up, about 1,000 participants developed dementia.
Researchers taught the computer to spot 13 tiny patterns in the sleep EEG recordings. These patterns include well‑known waves that help memory, such as slow delta waves and quick sleep spindles.
One surprising pattern, called kurtosis, shows big, sudden spikes in the signal. People with more of these spikes had a lower chance of dementia.
Even after accounting for education, smoking, weight, activity level, other health problems, and genetics, an older brain age still meant higher risk.
Because EEG can be recorded without surgery, the method could become a cheap way to check dementia risk at home. Future wearables might capture the needed brain waves while you sleep.
Improving sleep health may also slow brain aging. Earlier studies show that treating sleep problems changes brain‑wave patterns.
The research was funded by several U.S. government health agencies and the National Science Foundation.