A new study suggests that the way our brain behaves during sleep may reveal early signs of dementia risk, long before symptoms appear.
Researchers from the University of California, San Francisco, and Beth Israel Deaconess Medical Center in Boston have developed a method to estimate a person’s “brain age” using brain wave patterns recorded during sleep. Their findings were published in JAMA Network Open.
Dementia is a group of conditions that affect memory, thinking, and daily functioning. It is one of the leading causes of disability and death among older adults worldwide.
Because the disease develops slowly over many years, scientists are working hard to find ways to detect it as early as possible. Early detection could help people take steps to protect their brain health and delay the onset of symptoms.
In this study, researchers focused on brain activity during sleep. Sleep is not just a time for rest. It is a highly active process during which the brain carries out important tasks such as memory processing, repair, and clearing waste products.
Scientists have long believed that changes in sleep patterns may be linked to brain aging and diseases like dementia, but traditional measures of sleep have not provided clear answers.
To explore this further, the research team used electroencephalography, or EEG, a method that records electrical activity in the brain. They applied a machine-learning model that analyzed detailed patterns in brain waves during sleep. The model used 13 different features of these signals to estimate each person’s brain age.
The data came from around 7,000 adults aged between 40 and 94 years. None of the participants had dementia at the start of the study. They were followed for several years, ranging from about three and a half years to as long as 17 years. During this time, about 1,000 participants developed dementia.
The results showed a clear pattern. When a person’s estimated brain age was higher than their actual age, their risk of developing dementia increased.
For every 10-year difference where the brain appeared older, the risk of dementia rose by nearly 40 percent. On the other hand, if a person’s brain age appeared younger than their real age, their risk of dementia was lower.
The researchers found that detailed brain-wave patterns during sleep provided information that traditional sleep measures often missed. Earlier studies had looked at factors such as how long people slept or how much time they spent in different sleep stages, but these did not show strong links to dementia risk. This suggests that the fine details of brain activity may be more important than general sleep habits.
Certain types of brain waves were especially important in estimating brain age. For example, slow waves, known as delta waves, are linked to deep sleep and play a role in restoring the brain. Another pattern, called sleep spindles, is associated with memory and learning. These features helped the model understand how well the brain was functioning.
One interesting finding was that a pattern known as kurtosis, which appears as sudden large spikes in brain activity, was linked to a lower risk of dementia. This suggests that some types of brain activity during sleep may help protect cognitive health.
Importantly, the link between brain age and dementia risk remained strong even after the researchers considered other factors such as education, smoking, body weight, physical activity, and genetic risk. This means that sleep brain-wave patterns may offer unique information about brain health.
Because EEG signals can be collected without surgery or invasive procedures, the researchers believe this method could one day be used outside hospitals. For example, wearable devices might be able to track brain activity during sleep and provide early warnings about brain aging.
The findings also suggest that improving sleep health could help protect the brain. Previous research has shown that treating sleep disorders can change brain-wave patterns. Healthy habits such as regular exercise, maintaining a healthy weight, and reducing the risk of conditions like sleep apnea may support better brain aging.
However, the researchers caution that there is no simple solution or single treatment that can prevent dementia. More studies are needed to confirm these findings and explore how this method can be used in real-life settings.
In reviewing this study, it is clear that sleep plays a much more important role in brain health than previously understood. The use of machine learning to analyze detailed brain signals offers a powerful new way to detect early changes linked to dementia. While the results are promising, they also highlight the complexity of brain aging.
Future research will need to confirm how accurate and practical this method is for everyday use. Even so, the study provides strong evidence that paying attention to sleep health may be one of the most effective ways to support long-term brain function.
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