A study from October 2025 published in Alzheimer's & Dementia showed that people with reduced function in the brain’s glymphatic system have an increased risk of developing dementia.
The system, which is most active during sleep, removes waste products from the brain.
The researchers analyzed MRI scans from approximately 45,000 participants in the UK Biobank and identified biomarkers associated with the later development of dementia.
The study suggests that good sleep and stable blood pressure may be important for the brain’s long-term health.
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Interrupted breathing
Another study from 2025 published in JAMA Network Open examined the link between sleep apnea and small brain hemorrhages.
Over a period of eight years, the researchers found that people with moderate to severe sleep apnea had nearly double the risk of these changes.
According to the researchers, such microbleeds may increase the risk of both stroke and dementia.
However, the study could not determine whether treatment of sleep apnea reduces the risk.
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40 percent higher risk
A study from September 2025 published in Neurology investigated the association between chronic insomnia and the risk of cognitive impairment and dementia.
The study included 2,750 people with an average age of 70, all of whom were cognitively healthy at the start.
Around 16 percent of the participants had chronic insomnia.
Over an average follow-up period of 5.6 years, participants were regularly asked about their sleep habits, tested for memory and thinking, and examined with brain scans for changes associated with Alzheimer’s disease.
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At the end of the study, the results showed that people with chronic insomnia had a 40 percent higher risk of developing mild cognitive impairment or dementia compared with people without chronic insomnia.
Overall, the research indicates that sleep plays a central role in brain health, but that the effects only become visible many years later.
Sources: Medical News Today, Alzheimer's & Dementia, JAMA Network Open, and Neurology.
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