Chronic insomnia tied to 40% higher risk of dementia in older adults, study finds
Mayo Clinic-led research in Neurology follows 2,750 cognitively healthy adults for five years and links frequent sleep troubles to faster cognitive decline and brain changes
Older adults diagnosed with chronic insomnia were about 40% more likely to develop mild cognitive impairment or dementia over roughly five years of follow-up, according to a study published in Neurology.
Researchers who tracked 2,750 cognitively healthy participants with an average age of 70 found that those with chronic insomnia — defined as trouble sleeping at least three nights a week for three months or longer — experienced faster declines on annual memory and thinking tests and showed more brain changes commonly associated with preclinical dementia.
About 16% of the study cohort had a medical record diagnosis of chronic insomnia at baseline. During follow-up, 14% of those with chronic insomnia developed mild cognitive impairment or dementia compared with 10% of participants without an insomnia diagnosis. After adjusting for age, blood pressure, sleep medication use and sleep apnea, the investigators concluded that chronic insomnia was associated with a 40% higher risk of developing mild cognitive impairment or dementia — an effect the authors said was roughly equivalent to 3.5 additional years of aging.
The study team, including researchers affiliated with the Mayo Clinic and led by Dr. Diego Z. Carvalho, used annual cognitive testing for all participants and brain imaging for a subset to assess markers of neurodegeneration. Participants reporting sleep problems at the outset had lower baseline cognitive test scores and greater burdens of white matter hyperintensities and amyloid plaque on scans — features that researchers link to vascular damage and Alzheimer’s disease biology.
Participants who reported sleeping better than usual at study start tended to have fewer white matter hyperintensities during follow-up. The presence of the APOE ε4 gene, a known genetic risk factor for Alzheimer’s disease, was associated with steeper declines in thinking and memory across the cohort.
"Insomnia doesn’t just affect how you feel the next day — it may also impact your brain health over time," Dr. Carvalho said in a statement accompanying the paper. "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."
Sleep supports processes such as cellular repair, memory consolidation and clearance of metabolic waste from the brain. Prior research has associated poor sleep with a range of health problems, including cardiovascular disease, stroke and neurodegenerative disorders, and public health groups estimate that chronic insomnia affects a sizable portion of the population. The American Academy of Sleep Medicine has estimated that about 12% of Americans have chronic insomnia.
The investigators cautioned that the study has important limitations. The researchers relied on diagnoses recorded in medical records rather than standardized, study-specific assessments of insomnia severity, which may have missed undiagnosed cases and could understate symptom severity. Brain imaging was available only for a subset of participants, and observational data cannot definitively prove that insomnia causes dementia; associations could reflect shared underlying processes or reverse causation in which early brain changes disrupt sleep.
Nevertheless, the authors said the combination of cognitive testing, imaging signals and genetic interactions strengthens the evidence that sleep problems are tied to brain aging. They noted that treating chronic insomnia could have benefits beyond immediate sleep quality and might help protect cognitive health as people age.
Treatment options for chronic insomnia include behavioral approaches such as cognitive behavioral therapy for insomnia (CBT‑I), sleep hygiene measures (for example reducing late-night caffeine and alcohol), and, when appropriate, pharmacologic therapies supervised by clinicians. The study’s authors and outside sleep experts recommend that older adults who have persistent difficulty falling or staying asleep discuss symptoms with a health care provider, particularly if sleep problems begin or worsen alongside memory complaints or functional changes.
The findings add to a growing body of evidence linking sleep and brain health, but they underscore the need for further research that uses prospective sleep measurements, captures undiagnosed sleep disorders, and tests whether treating insomnia can slow cognitive decline. With aging populations worldwide and dementia rates expected to rise, identifying modifiable risk factors such as chronic sleep disturbance remains a priority for clinicians and public health authorities.
The study appears in Neurology, the medical journal of the American Academy of Neurology. The authors called for clinicians to consider sleep assessment in routine care for older adults and for trials to evaluate whether effective insomnia treatment changes the trajectory of cognitive aging.