Poor sleep may age your brain faster, scientists find in major study

A large MRI-based study of 27,500 adults finds that poor sleep may make the brain look up to a year older than its real age, suggesting that better sleep could slow brain ageing

A bad night’s sleep does not just make you cranky the next day, it could be making your brain age faster too. A large MRI-based study found that people with poor sleep patterns had brains that looked biologically older than their actual age, sometimes by as much as a year.

 

The research, titled Poor sleep health is associated with older brain age: the role of systemic inflammation and published in eBioMedicine, suggests that low-grade inflammation may help explain this link, raising hope that improving sleep could slow brain ageing.

 

Researchers at Karolinska Institutet, Sweden, and Tianjin Medical University, China, analysed brain MRI data from over 27,500 adults in the UK Biobank. Using machine learning, they found that poor sleep was linked to an older-looking brain, sometimes by as much as a year. The study also found that low-grade inflammation explains part of this connection, suggesting that better sleep may be a powerful tool to protect long-term brain health.

 

What did the study find?

The team used advanced brain imaging to estimate participants’ “brain age” and compared it with their actual age. Results showed that:

• For every one-point drop in a “healthy sleep score”, brain age looked about half a year older.
• People with poor sleep patterns had brains that appeared, on average, one year older than their chronological age.
• The effect was stronger in men compared to women.

The sleep score was based on five factors: being a morning person, getting seven to eight hours of sleep, not having insomnia, not snoring, and avoiding daytime sleepiness.

 

How does poor sleep accelerate brain ageing?

 

The researchers discovered that systemic inflammation plays a role. Inflammation accounted for up to 10 per cent of the link between poor sleep and an older-looking brain. Chronic inflammation is already known to harm blood vessels, accelerate neurodegeneration, and worsen diseases like dementia.

 

Other possible explanations include:

• Poor sleep reduces the brain’s ability to clear waste (glymphatic system)
• Cardiovascular health problems caused by bad sleep, which in turn harm the brain

Poor sleep linked to dementia: Study

According to the researchers, poor sleep has long been associated with a higher risk of dementia, but experts still debate whether sleep problems cause cognitive decline or are simply early warning signs. This study adds evidence that sleep itself may be a modifiable risk factor for brain ageing and potentially dementia.

How much sleep should you get for a healthier brain?

The sweet spot found in the study was seven to eight hours of quality sleep per night. Too little or too much sleep, frequent insomnia, late-night habits, snoring, or excessive daytime sleepiness all contributed to poorer brain outcomes.

Who is most at risk?

• Men: The association between poor sleep and faster brain ageing was stronger in males than in females.
• Middle-aged adults: While the effect was seen across ages, the strongest links appeared in people under 60.
• Those with unhealthy lifestyles: Higher BMI, smoking, and low physical activity often co-occur with poor sleep, amplifying risks.

Can fixing your sleep really slow down brain ageing?

While this study cannot prove cause-and-effect, it strongly suggests that improving sleep could protect brain health. Researchers recommend:

• Sticking to a regular sleep schedule
• Creating a dark, quiet, cool bedroom environment
• Avoiding caffeine and screens close to bedtime
• Seeking medical help for chronic insomnia or sleep apnoea

The study highlights that your sleep tonight may be shaping your brain health years from now. It says that sleep is a modifiable lifestyle factor, meaning you have the power to make changes. Better sleep hygiene may not only make you feel fresher in the morning but could also help keep your brain biologically younger and lower your risk of dementia. 

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This content is for informational purposes only and is not a substitute for professional medical advice.