Insomnia keeping you up at night? It may also raise your risk for dementia and cognitive impairment.

By Brett Arends

Sleep problems may be causing more than red eyes and poor performance at work

Between 10% and 20% of adults have trouble sleeping

Somewhere between 10% and 20% of us regularly struggle to get a good night's sleep, and the growing use of light-emitting tablets and phones at night is surely making matters worse.

But there is new evidence that those sleep problems may be causing more than red eyes, yawns and poor performance at work the next day.

Sleep is so important to brain health that insomnia is a major risk factor of cognitive impairment and even dementia, according to a new study of older adults conducted by the Mayo Clinic in Rochester, Minn.

Older adults with insomnia showed a "faster decline in global cognitive scores and 40% increased risk of CI [cognitive impairment]," researchers found after studying 2,750 adults with an average age of 70.

Most astonishingly, that 40% rise in the risk of cognitive impairment showed up within just six years, they found. The median period between first examination and follow-up was 5.6 years. (During that period about 10% of those with normal sleep patterns developed cognitive impairment in the period, and about 14% of those who had difficulties sleeping at least three nights a week.)

These studies always raise an obvious question about cause and effect. Does insomnia cause cognitive impairment or does cognitive impairment lead to insomnia? Diego Carvalho, assistant professor of neurology at the Mayo Clinic and lead author of the new study, says it may be a little of both.

"We cannot rule out the possibility that very early neurodegeneration (neuronal death) of neurons involved in sleep and circadian rhythm regulation could have contributed to insomnia," he confirms. "More likely than not, causality is bi-directional, with both poor sleep and early neurodegenerative changes contributing to each other."

But, he added, the study strongly suggests that interventions to improve your sleep patterns will help reduce your risk of cognitive decline.

"Because the study enrolled participants that were cognitively normal at baseline, there is hope that chronic insomnia is a modifiable risk factor, meaning that early intervention may prevent the cascade of events that contribute to the cognitive impairment," he says. "We still do not know how much intervening in one side only (insomnia treatment) can help in the long run, but there is good data suggesting significant improvements in cognitive function, mood, and quality of life in the short term."

Among the hopeful signs turned up by the research: that those who had insomnia, but who were able to get more sleep, showed measurable benefits in terms of brain health, including fewer physical signs of brain stress, in MRI scans.

"Participants with insomnia who reported sleeping more than they used to had less white-matter hyperintensities, suggesting that this might have offered some protection to the damage seen in those who reported reduced sleep," Carvalho reports. " We interpreted this finding as possible remission of insomnia symptoms, which is likely to be good for the brain."

When it comes to dealing with chronic insomnia, many people may immediately think of chemical interventions such as prescription sleeping pills or over-the-counter treatments such as melatonin. But Carvalho says the mainstream treatment is cognitive behavioral therapy for insomnia.

As the study focuses on older adults and covers a period of less than six years, it raises multiple disturbing questions. For instance: If the risk of cognitive impairment can rise by 40% in less than six years, what does it do over longer periods of time? And if this is happening to older adults, how much damage is sleep deprivation doing to younger adults over many decades?

(Oh, yes, and other new research has found that switching twice a year between standard and daylight-saving time is also messing with our body clocks and our health, including our sleep.)

It's often said that the invention of the electric lightbulb disrupted human beings' natural sleep patterns. That may go double or triple for the invention of the "smart" phone and tablet, which beam sleep-disturbing blue light straight into our eyes.

Such devices and their addiction are now so widespread that researchers have coined a new term, nomophobia, to describe the fear of not having your smartphone with you. And, yes, they have found a correlation between nomophobia and insomnia - either because people are staying up late on their phones, or they are so worried about the absence of their phone that they can't sleep.)

Modern e-ink e-readers, such as Amazon's Kindle (AMZN) and Rakuten's (JP:4755) Kobo, do not emit blue light and in many cases can be switched to a nighttime mode where the light is a warm yellow or even orange. Your correspondent can confirm that these are pretty good at ... (yawn) .... sending you ... off to ... zzzzzzz.

-Brett Arends

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09-20-25 1055ET