For this study, researchers recruited 2,750 adults with an average age of 70 who were cognitively healthy at the beginning of the study, and 16% of them had chronic insomnia.

Participants were tracked for an average of 5.6 years, and during that time were asked about their sleeping patterns, took thinking and memory tests, and had brain scans to look for white matter hyperintensities and beta-amyloid plaques, which are considered a hallmark of Alzheimer’s disease.

“We focused on studying the impact of insomnia on different markers of brain health to understand how insomnia may be related to cognitive decline,” Diego Z. Carvalho, MD, MS, sleep medicine specialist at the Mayo Clinic in Minnesota and lead author of this study, told Medical News Today. “Is it only through Alzheimer’s disease-related changes like amyloid, or also through cerebrovascular pathways affecting our white matter?”

At the study’s conclusion, researchers discovered that participants with chronic insomnia had a 40% higher chance of developing dementia or MCI than participants with non-chronic insomnia, which is reportedly equivalent to 3.5 additional years of aging.

“In our models, the impact of insomnia in the risk of MCI/dementia was higher than having two cardiometabolic conditions like hypertension and diabetes, or being 3.5 years older than your actual age, which are known risk factors,” Carvalho explained.

Additionally, researchers found that study participants who slept less than usual were more likely to have an increased amount of white matter hyperintensities and amyloid plaques in their brains.

“This helps to understand how insomnia may be related to cognitive decline,” Carvalho said.

“We found that insomnia with reduced sleep was not only associated with Alzheimer’s disease biomarkers like amyloid, but also with poorer cerebrovascular health with greater evidence for small vessel disease as shown by white matter hyperintensities. This is relevant because it supports that insomnia with reduced sleep may be related to two independent mechanisms that are known to contribute to cognitive decline.”
— Diego Z. Carvalho, MD, MS

“Insomnia remains widely under-recognized, under-reported, and undertreated in the community. Older patients often feel that it is normal to sleep poorly. Although there are indeed age-related changes that affect sleep quality, chronic insomnia goes much beyond that and cannot be equated to age-related changes,” he continued.

“Doctors need to include sleep assessment as part of any routine evaluation of patients of any age, but in particular older adults, as they tend to underreport sleep issues. Because of how prevalent insomnia in older adults is, this is a problem that cannot be constrained to management in sleep clinics,” he added.

CBT for chronic insomnia

“I would hope cognitive behavioral therapy for insomnia, the mainstream of therapy for insomnia, could be implemented in primary care settings across the country. The advent of online treatment options through apps or courses have facilitated access but there is much more work to be done.”
— Diego Z. Carvalho, MD, MS

MNT spoke with Christopher Allen, MD, a board-certified sleep medicine physician, pediatric neurologist, and sleep science advisor at Aeroflow Sleep. He commented that he found this study both important and clinically plausible, with findings that align with what he sees in his clinic.

“This study’s signal touches multiple pathways: cognition, amyloid biology, and cerebrovascular integrity,” he continued. “Understanding those links helps us personalize care by screening for comorbid sleep apnea, mood symptoms, and cardiometabolic risk. These treatments actually consolidate sleep. The public-health upside is huge because improving sleep is a lever patients can pull.”

Insomnia more than just ‘feeling tired’

“Long-standing insomnia is more than just ‘feeling tired’ — it can track changes in attention, memory, and processing speed over time. Insomnia is common, underdiagnosed, and very treatable. The gold standard is cognitive behavioral therapy for insomnia (CBT-I). If persistent insomnia is a marker or even a modest contributor to brain vulnerability, then identifying and treating it becomes part of brain-health prevention, not just symptom relief.”
— Christopher Allen, MD

For the next steps of this research, Allen said he would like to see interventional trials, objective sleep measurement, and broader, longer, and more diverse cohorts.

“(I) would also like to clarify how hypnotic use, where this study found no association with worse outcomes overall, interacts with specific phenotypes like short-sleep insomnia,” he added.

MNT also spoke with Megan Glenn, PsyD, clinical neuropsychologist in the Center for Memory and Healthy Aging at Hackensack Meridian Neuroscience Institute at Jersey Shore University Medical Center in New Jersey, about this research.

“Insomnia is one of the most common concerns I see in older adults worried about memory. This study is encouraging because it links poor sleep not just to cognitive symptoms, but to measurable brain changes and future risk of decline. It reinforces sleep as a tangible lever we can act on in the quest to prevent or slow the trajectory of developing dementia.”
— Megan Glenn, PsyD

“Most cases of dementia develop from many small risk factors adding up over decades,” she continued. “The more modifiable targets we find — like sleep, blood pressure, hearing, and physical activity — the more we can combine them into meaningful protection. Research suggests roughly 45% of dementia cases could be delayed or prevented by addressing these factors.”

“We need studies using objective sleep measures, not just self-report or chart review, to clarify which aspects of sleep matter most,” Glenn added. “It’s also critical to test whether treating insomnia — through behavioral therapy or medications — actually changes cognitive outcomes and brain biomarkers.”