Your sleeping brain might be giving away more than a rough night. A new study suggests it may also flag dementia risk years before memory problems show up.
Researchers at UC San Francisco and Beth Israel Deaconess Medical Center used machine learning to analyse EEG recordings taken during sleep and estimate a person’s “brain age”. They found dementia risk was higher when the brain appeared older than the person’s actual age.
For every 10-year increase between estimated brain age and chronological age, the likelihood of developing dementia rose by nearly 40 percent. People whose estimated brain age was younger than their actual age had a lower risk.
The findings were published in JAMA Network Open.
The team built the model using 13 microscopic features found in EEG brain wave recordings. They then applied it to data from about 7,000 adults who took part in five separate studies.
Participants were aged 40 to 94, and none had dementia when their studies began. Researchers followed them for 3.5 to 17 years. During that time, about 1,000 participants developed dementia.
The analysis found that small, detailed patterns in sleeping brain waves may reveal information that standard sleep measures miss. Previous pooled analyses had found no meaningful link between dementia risk and common sleep measurements, including time spent in different sleep stages and how efficiently someone stayed asleep overnight.
“Broad sleep metrics don’t fully capture the complex multidimensional nature of sleep physiology,” said senior author Yue Leng, MBBS, PhD, associate professor of psychiatry at the UCSF School of Medicine.
Several of the EEG patterns used to calculate brain age are already linked to memory and cognitive health. They include delta waves, the slow electrical patterns associated with deep sleep, and sleep spindles, brief bursts of rapid brain activity believed to help the brain strengthen and store memories.
One of the study’s standout findings involved large, sudden spikes in EEG signals. That feature, known as kurtosis, was tied to a lower risk of developing dementia.
The link between an older estimated brain age and higher dementia risk remained significant after researchers accounted for education, smoking, body mass index, physical activity, other medical conditions and genetic risk factors.
The researchers said sleep-based brain age measurements could eventually help assess dementia risk outside traditional clinics, because EEG readings can be collected without invasive procedures. They said future wearable devices might be able to record the needed brain signals during sleep.
“Brain age is calculated from sleep brain waves,” Leng said. “We know that brain activity during sleep provides a measurable window into how well the brain is aging.”
The results also suggest sleep health may affect how the brain ages. Leng noted that previous research has shown treating sleep disorders can change brain wave activity recorded during sleep.
“Better body management, such as lowering body mass index and increasing exercise to reduce the likelihood of apnea, may have an impact,” said first author Haoqi Sun, PhD, assistant professor of neurology at Beth Israel Deaconess Medical Center, who developed the model with two co-authors. “But there’s no magic pill to improve brain health.”
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