People who don’t sleep well may have brains that look older than they really are, according to a large brain imaging study from Karolinska Institutet in Sweden.
The study, published in the journal eBioMedicine, found that poor sleep habits are linked to faster brain aging—and inflammation in the body may be part of the reason.
Scientists already know that poor sleep is linked to a higher risk of dementia. But it’s been unclear whether bad sleep causes brain decline or is just an early sign of it.
In this new study, researchers looked at how sleep affects brain age compared to actual age.
The team used data from 27,500 middle-aged and older adults in the UK Biobank. All of them had MRI brain scans, which were used to estimate how “old” their brains looked using artificial intelligence.
The AI looked at more than a thousand features from the brain scans to calculate a biological brain age.
Sleep quality was rated using five self-reported factors: whether someone is a morning or evening person, how long they sleep, if they have insomnia, whether they snore, and if they feel sleepy during the day.
Each person got a sleep score from 0 to 5. A score of 4 or higher was considered healthy, 2–3 was intermediate, and 1 or lower was poor sleep.
The researchers found that for every one-point drop in sleep score, a person’s brain appeared about six months older. People with the lowest scores—those with the worst sleep—had brains that looked about a year older than their actual age.
To understand why this happens, the team also looked at signs of low-grade inflammation in the body. They found that inflammation explained about 10% of the connection between poor sleep and older-looking brains.
“These results suggest that not sleeping well might actually speed up how quickly your brain ages,” said lead researcher Abigail Dove from Karolinska Institutet. “And since sleep is something we can improve, it might be possible to slow down brain aging and even prevent memory problems by getting better sleep.”
The researchers said there may be other explanations, too. For example, poor sleep could interfere with the brain’s waste removal system, which works mainly while we sleep. Or bad sleep could harm heart and blood vessel health, which affects the brain as well.
It’s important to note that the sleep data came from people answering questions about their own habits, which isn’t always accurate. Also, people in the UK Biobank tend to be healthier than the general population, which might limit how well the results apply to everyone.
The research was a global effort, involving teams from Sweden and China. It was supported by several foundations and research councils, including the Alzheimer’s Foundation and the Swedish Research Council.
If you care about dementia, please read studies about Common drug for constipation is linked to higher dementia risk and findings of Scientists find link between heartburn drugs and increased dementia risk.
For more about dementia, please read studies about Scientists find a drug related to Viagra may help treat vascular dementia and findings of link between body inflammation and dementia risk.
The study is published in eBioMedicine.
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