A restless night can leave you groggy the next day. But when sleeplessness becomes chronic, the toll extends beyond fatigue. A new study suggests that insomnia may influence how quickly the brain ages, reshaping memory and thinking over time.
The researchers found that chronic insomnia increases the risk of cognitive decline. People who struggled with sleep at least three nights a week for three months or more had a 40% higher chance of developing mild cognitive impairment or dementia.
This translates to the effect of adding 3.5 years of brain aging. The researchers emphasize that the study reveals an association, not direct causation.
“Insomnia doesn’t just affect how you feel the next day – it may also impact your brain health over time,” said Dr. Diego Z. Carvalho of the Mayo Clinic, who is a member of the American Academy of Neurology.
“We saw faster decline in thinking skills and changes in the brain that suggest chronic insomnia could be an early warning sign or even a contributor to future cognitive problems.”
Insomnia and brain aging
The research team followed 2,750 older adults, with an average age of 70, for more than five years. Of these participants, about 16% struggled with chronic insomnia. At the beginning, everyone answered questions about whether their sleep had changed in the past two weeks.
The participants also took yearly tests designed to measure memory, attention, and other thinking skills.
A smaller group had detailed brain scans to look for warning signs, including white matter damage from small vessel disease and amyloid plaques, the sticky protein often linked to Alzheimer’s.
As the years passed, patterns began to emerge. People with chronic insomnia were more likely to see their thinking and memory decline. Fourteen percent of them developed mild cognitive impairment or dementia, compared with just 10% of those who slept normally.
That difference may sound small, but when applied to thousands of people, it becomes significant. Even after researchers adjusted for other health factors like age, high blood pressure, sleep apnea, and use of sleep medications, the insomnia group still carried a 40% higher risk.
This finding suggests that the effects of poor sleep cannot be fully explained by other medical conditions. Instead, insomnia itself may be playing a more direct role in how the brain ages.
Losing sleep impacts the brain
The researchers compared two groups: people sleeping less than usual and those sleeping more. The contrast was clear. Those getting less sleep scored lower on memory and thinking tests, as if their brains had aged four extra years.
Brain scans confirmed the findings. People with less sleep had more brain damage and more amyloid plaques, the proteins tied to Alzheimer’s.
The buildup looked like what is seen in people with a dementia risk gene. This suggests that losing sleep often can make the brain age faster and become weaker.
For those sleeping more, the outlook was brighter. Their brain scans showed less damage, hinting that extra rest might help recovery, even if scientists don’t yet know how.
The link between insomnia and aging
Certain groups proved especially vulnerable. Participants with the APOE ε4 gene experienced sharper declines in memory and thinking. This finding highlights how insomnia may interact with genetic risks to accelerate cognitive problems.
“Our results suggest that insomnia may affect the brain in different ways, involving not only amyloid plaques, but also small vessels supplying blood to the brain,” said Dr. Carvalho.
“This reinforces the importance of treating chronic insomnia – not just to improve sleep quality but potentially to protect brain health as we age. Our results also add to a growing body of evidence that sleep isn’t just about rest – it’s also about brain resilience.”
The study used medical records to find people with insomnia. This means some cases might have been missed, or the seriousness of symptoms not fully recorded.
Even so, the results show how harmful poor sleep can be over time. They highlight the need to check sleep problems more carefully, treat them sooner, and teach people why sleep is important for healthy aging.
The research was funded in part by the National Institutes of Health.
The study is published in the journal Neurology.
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