Chronic Insomnia Tied to 40% Higher Dementia Risk

What the Mayo Clinic Found

A large Mayo Clinic study tracked 2,750 cognitively healthy older adults over an average of 5.6 years and found that chronic insomnia – defined as trouble sleeping at least three nights a week for three months or more – was associated with a 40% higher risk of developing mild cognitive impairment or dementia compared to those without the condition. The research was published in the September 2025 issue of Neurology, the medical journal of the American Academy of Neurology. The study does not prove that insomnia causes cognitive decline – it establishes an association – but the strength of the findings has drawn significant attention from sleep and brain health researchers.

CNN and ScienceDaily reported on the study’s findings, which were described by lead author Dr. Diego Carvalho, a Mayo Clinic neurologist and sleep specialist, as a signal that insomnia may be more than an inconvenience. “Insomnia doesn’t just affect how you feel the next day – it may also impact your brain health over time,” Carvalho said in the study’s announcement.

The Cognitive Toll of Lost Sleep

Among study participants with chronic insomnia, 14% developed mild cognitive impairment or dementia over the follow-up period, compared to 10% of those without insomnia. That difference remained after researchers accounted for factors including age, high blood pressure, sleep apnea, and sleep medication use.

For those with insomnia who were also getting less sleep than usual during the prior two weeks, the cognitive profile was particularly concerning. Their test scores at the start of the study were comparable to those of people four years older, according to the Mayo Clinic analysis. They also showed higher rates of white matter hyperintensities and amyloid plaques – two brain changes associated with vascular aging and Alzheimer’s disease pathology.

How Sleep Affects the Brain

Researchers point to the brain’s glymphatic system as a key mechanism. During deep sleep, cerebrospinal fluid moves through the brain and clears metabolic waste – including amyloid-beta and tau proteins linked to Alzheimer’s disease. When sleep is consistently disrupted, that clearing process is impaired, allowing these proteins to accumulate over time. According to Dr. Carvalho, the study’s findings suggest insomnia affects brain health through multiple pathways, involving both amyloid plaques and small blood vessels supplying the brain.

Dr. Esther Oh, a Johns Hopkins neurologist who was not involved in the research, told CNN that poor sleep can increase neuroinflammation and impair synaptic plasticity – both factors connected to cognitive decline. Those mechanisms help explain why the insomnia group showed not just higher rates of impairment but also faster rates of cognitive decline on annual testing.

A Modifiable Risk Factor

One of the study’s most significant implications is that insomnia, unlike genetics, is potentially treatable. The research found that participants with insomnia who increased their sleep time or used medication during the study period did not show the same degree of cognitive risk as those who remained chronically sleep-deprived. That finding positions sleep as a modifiable target for cognitive health in a way that fixed risk factors such as age or genetic profile are not.

Cognitive behavioral therapy for insomnia, known as CBTI, is currently the recommended first-line treatment. It focuses on behavioral changes rather than medication and has demonstrated effectiveness in clinical settings. As Carvalho noted, the goal is not simply better sleep – it may also be a measurable contribution to long-term brain resilience.

References: Chronic Insomnia Linked to 40% Higher Dementia Risk, Mayo Clinic Study Finds | Chronic Insomnia Raises Dementia Risk by 40 Percent