Your birth certificate may say one age, but electrical activity recorded from your brain during sleep can suggest something very different. Researchers have now found that the larger this gap becomes, the more strongly it may be associated with future dementia risk.
Scientists used sleep EEG recordings to estimate what they called a person’s “brain age” and compared that figure with their actual chronological age.
Across thousands of older adults followed for years, people whose sleeping brains appeared substantially older than their real age were more likely to develop dementia later on.
Researchers estimated brain age from electrical activity during sleep
Sleep may look like a period of inactivity, but the brain continues producing complex electrical patterns throughout the night. Researchers used those patterns to estimate how old a person’s brain appeared based on its activity.
In the JAMA Network Open study, researchers analyzed sleep EEG data from 7,105 adults across five long-running community studies.
EEG, or electroencephalography, measures electrical activity in the brain using electrodes placed on the scalp.
The researchers used machine learning to analyze multiple features within those sleep recordings and calculate an estimated brain age.
They then subtracted each participant’s actual age from that estimate.
That difference became the brain age index, or BAI.
A person whose EEG-based brain age closely matched their chronological age would have a relatively small gap. Someone whose brain activity resembled that of a person 10 or 20 years older would have a larger positive brain age index.
Takeaway: Researchers turned sleep-related electrical signals into an estimate of biological brain aging and compared it with each person’s real age.
Every extra 10 years was tied to about 39% higher dementia risk
The most striking finding came when researchers followed participants to see who later developed dementia. A larger gap between sleep-based brain age and actual age was consistently associated with greater risk.
Across the five cohorts, 1,082 participants developed dementia during follow-up periods ranging from about 3.6 to 16.9 years.
For every 10-year increase in the brain age index, dementia risk was about 39% higher after researchers accounted for factors including age, sex, education, body mass index, smoking, race and ethnicity, physical activity, and sleep medication use.
The relationship remained even after researchers added other major factors linked with dementia, including sleep apnea severity, diabetes, hypertension, heart attack, stroke, depression, baseline cognition and APOE ε4 genetic status.
That does not mean someone whose sleeping brain appears 10 years older has a 39% chance of developing dementia. The figure describes a relative increase in risk associated with each 10-year increase in the brain age index.
Related: 8 Common Bedroom Mistakes That Could Be Could Be Sabotaging Your Sleep
Takeaway: A sleeping brain that appeared older than expected was associated with a meaningfully higher risk of dementia later in life.
The signal appeared to reveal something ordinary risk factors did not
One reason the findings are interesting is that the brain age measurement appeared to provide information beyond several factors doctors already use when thinking about dementia risk.
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The association remained after accounting for APOE ε4, one of the best-known genetic risk factors for Alzheimer’s disease. It also remained after researchers adjusted for baseline cognition and common health conditions.
That suggests the EEG measurement may be capturing a different aspect of brain health: neurophysiological aging.
Sleep patterns change with normal aging. Deep sleep generally declines, sleep becomes more fragmented, and the electrical features of different sleep stages can shift.
Changes can become more pronounced with neurodegenerative disease. By analyzing many of these signals at once, the machine-learning model may detect subtle patterns that are difficult to see during an ordinary sleep-study interpretation.
Takeaway: Sleep EEG brain age may contain information about neurological aging that is not fully explained by genetics, existing health conditions or someone’s actual age.
Researchers found the pattern across five different groups
The result was not based on a single group of patients from one hospital. Researchers combined data from five separate community-based studies, giving them an opportunity to see if the relationship held up across different populations.
Those cohorts included the Multi-Ethnic Study of Atherosclerosis, the Atherosclerosis Risk in Communities study, the Framingham Heart Study Offspring Study, the Osteoporotic Fractures in Men Study and the Study of Osteoporotic Fractures.
The relationship between higher brain age index and dementia appeared across age groups and in both men and women.
Researchers also conducted sensitivity analyses that removed cohorts where dementia identification relied more heavily on medical records. The overall relationship remained.
That consistency strengthens the case that the EEG signal is detecting something meaningful, though the researchers stress that more work is needed before it could become a routine clinical screening tool.
Takeaway: The association appeared repeatedly across multiple long-term studies rather than depending on one isolated dataset.
This could matter years before dementia becomes obvious
The biggest potential value may not be diagnosing dementia after symptoms appear. It may be identifying signs of accelerated brain aging much earlier.
Dementia develops gradually, and biological changes can begin years before memory loss or other symptoms become severe enough for diagnosis. A sleep EEG is already used in medical settings to evaluate conditions such as sleep apnea and other sleep disorders.
If researchers can validate this brain age measurement further, the same type of recording might eventually provide information about future neurological risk.
The researchers also noted that advances in wearable EEG technology could make brain-age measurements more accessible outside specialized sleep laboratories.
For now, this is not a test people can use on their own to determine if they will develop dementia.
The study found an association, not certainty. Some people with an older-appearing brain will never develop dementia, and many factors influence cognitive aging. Still, the findings point to a striking possibility: clues about the brain’s future health may already be visible in its electrical activity while a person is asleep.
Question for you. Would you want to know if a sleep test suggested your brain was aging faster than your actual age?
