Chronic insomnia doubles dementia risk, study finds
Chronic insomnia may accelerate brain ageing by three years and raises dementia risk by 40 per cent, according to new research.
The study tracked 2,750 cognitively healthy older adults with an average age of 70 for more than five and a half years.
Those with the sleep disorder were far more likely to develop cognitive impairment.
Researchers at the Mayo Clinic found that 14 per cent of people with chronic insomnia developed mild cognitive impairment or dementia during the study period, compared with 10 per cent of those without the condition.
Around 16 per cent of participants had chronic insomnia, defined as persistent difficulty falling or staying asleep.
The results suggest insomnia could be a modifiable risk factor for decline.
During sleep, the brain clears waste products and restores function — processes thought to be disrupted in those with ongoing sleep problems.
Interestingly, participants with chronic insomnia who reported sleeping longer than usual had fewer white matter spots in the brain — a sign of small vessel disease.
However, they still scored lower on thinking tests after adjusting for age, high blood pressure, medication use and sleep apnoea.
Dr Diego Z. Carvalho of the Mayo Clinic in Rochester, Minnesota, and a member of the American Academy of Neurology, said: “Participants with chronic insomnia with perceived reduced sleep duration had poorer brain health, according to brain imaging findings linked to Alzheimer’s disease and cerebrovascular disease.
“The study emphasises that even a short period of chronic insomnia can lead to potential detrimental cognitive effects later in life.”
Carriers of the APOE ε4 gene, which increases Alzheimer’s risk, showed greater declines in memory and thinking skills when they also had chronic insomnia.
Dr Marc Siegel, senior medical analyst for Fox News in New York, who was not involved in the study, said it shows an “important association” between sleep deprivation and cognitive decline.
“We already know that the brain self-cleanses waste products during sleep, and that sleep is restorative to brain cells — but we still don’t know whether the effect observed here is directly due to inattention from sleeplessness (on testing) and memory effects that could be short term,” he said.
“The issue of actual neurodegeneration due to insomnia is probable, but not proven by this study.”
Siegel added that cognitive decline could stem directly from the insomnia itself or from the breakdown of brain function that occurs as a result.
The study had limitations, including no tools to assess insomnia severity over time and no long-term objective sleep data.
Researchers also could not adjust for which patients were treated for sleep apnoea, such as with CPAP machines.
“We also did not have full information on the duration of usage or doses of sleep medication,” Carvalho noted, adding that the study shows association rather than direct causation.
Experts recommend simple steps to improve sleep, such as avoiding caffeine late in the day, reducing alcohol, steering clear of large meals or exercise before bed, and limiting electronics use in the evening.
Carvalho warned against obsessing over sleep tracking, which can create “performance anxiety” that worsens sleep.
“Tracking does not help with your sleep — good sleep practices do,” he said.
He also urged caution with medication: “Although sleep medications can help and are available for patients with chronic insomnia, they do not work very well in the long run if good sleep practices are not adopted.
“There is no solution for poor sleep issues that does not start with the patient doing the right things.”
