By Dr. K. Nicole Mims, board-certified sleep physician
I've always felt that sleep is essential for brain health. It's one of the reasons I went into sleep medicine from neurology. So when a big 2025 study in Neurology tied chronic insomnia to memory and brain scans, and included a finding about sleep aids that surprised me, it became my favorite study of the year.
Why Mayo Clinic researchers ran this study
They wanted to know what chronic insomnia does to older adults whose memory and thinking are still normal, and how it affects their thinking over the years. Chronic insomnia here means trouble sleeping at least three nights a week for three months or more.
The study
The participants came from the Mayo Clinic Study of Aging:
2,750 adults for thinking scores and 2,814 for dementia risk
Average age about 70, followed for a median of 5.6 years
1,027 had MRI scans and 561 had amyloid PET scans
The scans
On MRI, white-matter hyperintensities are bright spots in the brain's wiring. They usually reflect wear on tiny blood vessels, they're tied to blood pressure and vascular health, and they're linked to memory decline. An amyloid PET scan measures amyloid plaque, a hallmark of Alzheimer's disease, in units called centiloids.
What they found
People with chronic insomnia had a faster drop in thinking scores and developed memory problems sooner: 14% developed mild cognitive impairment or dementia, compared with 10% without insomnia. That's about 40% higher risk, which the authors compare to being about three and a half years older.
Short sleep vs. normal sleep
The biggest contrast was insomnia with less sleep versus insomnia with more sleep. People with insomnia who were sleeping less than usual started out with lower thinking scores, more white-matter changes and more amyloid. People with insomnia who were sleeping more than usual had fewer white-matter changes.
Notably, insomnia didn't speed up the buildup over time or change the slope of the curve.
Sleep aids: the part that surprised me
So many of my patients with insomnia have been scared away from sleep medications, and they keep struggling. Here's what this study found: among people with insomnia, sleep aid use showed no link to worse thinking scores or higher risk of cognitive impairment. In this study, sleep aids didn't look harmful. Note that the study grouped sleep aids together rather than looking at each drug.
There was an early hint of decreased white matter hyperintensity for short sleepers who used sleep aids, but it was exploratory, inconsistent across groups, and the study didn't track whether sleep aids changed how long people slept, so it isn't proof of a benefit. My hypothesis is that they got more sleep, and that this helped protect white matter. We'd need a more specific study design to know.
The honest part: limits
It's observational: a link, not cause and effect.
The "sleeping less / more" groups came from one question on the Beck Depression Inventory about the past two weeks. It's subjective, with no hours of sleep measured.
There was no objective sleep data.
Talk to your doctor
If you've been afraid of sleep aids, this is reassuring. But it isn't a reason to start or stop any medication. Talk to your doctor about what's right for you.
The big takeaway
Sleep matters for your brain. I treat insomnia like blood pressure: a chronic condition we can manage together. If that sounds like you, we can help at Luminary Sleep.
References
Carvalho DZ, et al. Associations of Chronic Insomnia, Longitudinal Cognitive Outcomes, Amyloid-PET, and White Matter Changes in Cognitively Normal Older Adults. Neurology. 2025;105(7):e214155. doi:10.1212/WNL.0000000000214155
American Academy of Neurology press release, "Chronic insomnia may speed up brain aging," Sept. 10, 2025. https://www.aan.com/pressroom/home/pressrelease/5282