Insomnia and the Brain: Why Persistent Sleepless Nights Deserve Attention

Most of us have known nights when sleep simply would not come. We lie awake, watch the clock and get through the next day on willpower and coffee. For many people this happens now and then and passes. For others it settles in and becomes the way their nights usually go.

A new review from a group of European neurologists suggests that this second kind of sleeplessness deserves more attention than it usually gets, and not only because of how tired it leaves us.

How does chronic insomnia affect the brain?

In the short term, weeks of poor sleep blunt attention, slow our reactions and make new memories harder to keep, because the brain uses deep sleep to file away what it learned during the day. Sleep also seems to help the brain clear out waste, including proteins linked to Alzheimer's disease, although most of that evidence comes from animal and short-term studies. Over the long term, chronic insomnia is linked to a higher risk of stroke and, less firmly, to dementia. Linked is the key word: these studies show the two travel together, not that one causes the other. The review below is the largest look at that question so far.

What the researchers did

The review was funded by the European Academy of Neurology and published at the end of September in the journal Sleep Medicine Reviews. It was led by Luca Vignatelli of the Institute of Neurological Sciences in Bologna, with colleagues from Austria, Germany, Italy and Switzerland.

Instead of running a new study, the team gathered the evidence that already exists. They searched two large medical databases for systematic reviews on insomnia and health, and added three new reviews of their own on stroke, injuries at work and hospital admissions. Altogether they looked at seven kinds of health outcome. The stroke analysis alone included more than 1.3 million people.

Insomnia here means more than a bad night. It means having trouble falling asleep or staying asleep, and feeling the effects during the day, even though there is enough time and opportunity to sleep. An earlier analysis estimated that around 22 percent of people meet the criteria for it.

What they found

People with insomnia had a 26 percent higher risk of stroke than people without it. The size of that link varied a great deal from one study to the next, so the true figure could be smaller or larger. People with insomnia also had 28 percent higher odds of being admitted to hospital for any reason.

Insomnia was also linked with depression and other mental health problems. On dementia, the picture was less clear. Most of the existing reviews found a link between insomnia and dementia in general, but not all of them did. The evidence was more consistent for Alzheimer's disease, and mixed for vascular dementia.

What this does and does not mean

It is important to be clear about what a review like this can show. It brings together studies that observed people over time. Those studies can show that insomnia and these health problems tend to occur together, but they cannot show that insomnia causes them.

The relationship may run in more than one direction. Depression and anxiety make sleep harder, and poor sleep can make low mood and worry worse. Some illnesses disturb sleep long before they are diagnosed. Insomnia may be a cause, a consequence or an early sign, and often it may be a mix of all three.

One of the authors, Stefan Seidel of the Medical University of Vienna, was keen to make this point. He said people should not be frightened by these results, because a higher risk across a whole population does not mean that any one person with insomnia will develop dementia or have a stroke.

The honest limits

The studies in the review did not all define insomnia in the same way, which makes them harder to combine. Few of them took proper account of sleep medication, which some people with insomnia take and which could affect the results. The authors themselves point out both limits.

Why this is useful news

The hopeful part of this story is that insomnia is not something you simply have to put up with. It is common, and it can be treated.

The approach most often recommended first for long-term insomnia is a form of cognitive behavioural therapy designed for sleep. It helps people change the habits and thoughts that keep them awake, for example by keeping regular sleep times and not spending long hours lying awake in bed. It takes some effort, but many people find it worthwhile.

Everyday habits help too. Going to bed and getting up at roughly the same time, keeping the bedroom cool and dark, putting screens away for a while before bed, and having coffee and alcohol earlier in the day are all simple places to start.

The researchers' wider message is that sleep should be part of every conversation about brain health, at any age. If your nights have been difficult for weeks or months, that is a good reason to mention it to your doctor, rather than something to quietly live with.

A small, steady habit

Good sleep tends to come from a calm, regular rhythm to the day. Treeny is built around that same idea of small things done regularly. The daily exercises are short and meant to be enjoyed, and Flo, the coach inside the app, adjusts them to how you are doing each day. It is one gentle way to keep your mind active during the day. It is not a treatment for insomnia or for anything described in this article.

A note on how to read this

This article describes research and is not medical advice. The review discussed shows associations and cannot show that insomnia causes stroke, dementia or other conditions, or that treating insomnia prevents them. If you have been sleeping badly for a long time, or if you are worried about your memory or your mood, speak to your doctor, who knows your situation in a way no article can.