Struggling to sleep could be damaging you more than feeling groggy the next day, after scientists found ongoing sleep problems can increase your dementia risk. A new US study found older adults with chronic insomnia faced a 40 percent higher risk of developing mild cognitive impairment or dementia compared with those without – equivalent to 3.5 additional years of brain aging.
Paper author Diego Carvalho of the Mayo Clinic in Rochester, Minnesota, explained: “Insomnia doesn’t just affect how you feel the next day—it may also impact your brain health over time. 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.”
The researchers followed 2,750 cognitively healthy adults aged over 50, with an average age of 70, for around five-and-a-half years. Of the participants, 16 percent reported chronic insomnia, defined as difficulty sleeping at least three nights a week for three months or more.
At the start, participants reported their recent sleep patterns, took annual memory and thinking tests, and some underwent brain scans.
The team looked for white matter hyperintensities—areas of brain tissue damage linked to small vessel disease—and amyloid plaques, the protein deposits tied to Alzheimer’s disease.
By the end of the study, 14 percent of those with chronic insomnia developed mild cognitive impairment or dementia, compared with 10 percent of participants without insomnia.
Dr Carvalho added: “Our results suggest that insomnia may affect the brain in different ways. This reinforces the importance of treating chronic insomnia—not just to improve sleep quality but potentially to protect brain health as we age.”
Writing in The Conversation Timothy Hearn, Senior Lecturer in Bioinformatics at Anglia Ruskin University, explained the US study’s findings as showing that “insomnia paired with shorter-than-usual sleep was especially harmful.”
Dr Hearn added: “These poor sleepers already performed as if they were four years older at the first assessment and showed higher levels of both amyloid plaques and white-matter damage.
“By contrast, insomniacs who said they were sleeping more than usual, perhaps because their sleep problems had eased, had less white-matter damage than average.
“Why do both amyloid plaques and blood-vessel damage matter? Alzheimer’s disease isn’t driven by amyloid alone. Studies increasingly show that clogged or leaky small blood vessels also speed cognitive decline, and the two disease states can magnify each other.
“White-matter hyperintensities disrupt the wiring that carries messages between brain regions, while amyloid gums up the neurons themselves.
“Finding higher levels of both in people with chronic insomnia strengthens the idea that poor sleep may push the brain towards a double hit.
“These findings add to a growing body of research, from middle-aged civil servants in the UK, to community studies in China and the US, showing that how well we sleep in midlife and beyond tracks closely with how well we think later on.
“Chronic insomnia appears to accelerate the trajectory towards dementia, not through one pathway but several: by boosting amyloid, eroding white matter and probably raising blood pressure and blood-sugar levels too.”
Dr Hearn added that cognitive behavioural therapy for insomnia, delivered in person or digitally, remains the gold-standard treatment and improves sleep in around 70 percent of patients.
He went on: “So the relationship is unlikely to be as simple as ‘treat insomnia, avoid dementia’.
“Poor sleep often co-exists with depression, anxiety, chronic pain and sleep apnoea – all of which themselves hurt the brain. Unravelling which piece of the puzzle to target, and when, will take rigorously designed long-term studies.”
Professor Jason Ellis—a sleep researcher at Northumbria University in England, who was not involved in the US study—said: “There is evidence that we clear toxins from the brain during sleep, specifically one called beta amyloid, which has also been associated with cognitive decline and neurodegenerative disorders.
“As such, a lack of consolidated slow wave sleep, over a long period of time, may well increase the risk of cognitive decline.
“Moreover, Slow Wave Sleep [also known as deep sleep] helps us regulate our endocrine system and immune system and both systems have also been implicated as risk factors for neurodegenerative disorders.”