Scientists are now discovering that the way you sleep, and how consistently you do it, has a powerful impact on brain health, memory, and even your risk of dementia
So if you've been cutting corners on rest, thinking you'll “catch up later,” you may want to think again.
How does sleep affect my brain?
A Sleep has a huge impact on brain health. As a snapshot, while you snore and dribble away, your brain removes waste products and consolidates memories, plus it processes emotional experiences and slashes stress. It’s also the time where your brain forges connections between seemingly unrelated ideas, so that once you wake you’re an expert problem solver. In theory, anyway.
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It highlights why insufficient sleep can result in your brain and body malfunctioning. According to research, 24 hours without sleep reduces performance to the level of someone with a blood alcohol concentration of 0.10%, which is the equivalent to being legally drunk. One to three days of tossing and turning results in poor moods, impaired judgement and reduced creativity. After a week or two, you’re feeling foggy and forgetting things. After a week or two, you’re feeling foggy and forgetting things…
Long-term, well, that’s when the real problems start as you’re not only at a higher risk of depression but, according to recent research, you endure premature sleep ageing that heightens the risk of dementia.
How much does lack of sleep age the brain?
“We found that people with poor sleep had brains that appeared one year older than expected based on their chronological age, while those with a healthy sleep profile showed no such gap,” explains Abigail Dove, researcher at the department of neurobiology at the Karolinska Institute in Sweden. “A year may not sound like much, but in terms of brain health, it matters. Even small accelerations in brain ageing can compound over time, potentially increasing the risk of cognitive impairment, dementia and other neurological conditions.”
“Our study used data from 27,500 UK Biobank participants with available information on both sleep and brain MRI,” Dove continues. “At the beginning of the UK Biobank study, participants underwent a thorough examination, provided blood samples and reported detailed information about lifestyle behaviours like sleep. Approximately nine years later, participants were invited back for a brain MRI scan.”
After applying a machine-learning model to the scans of the healthiest participants, Dove and her team applied it to the full population. Those whose brain age was older than their chronological age showed greater signs of brain-tissue loss, thinning of the cortex and damage to blood vessels – all signs of deterioration.
“Sleeping more or less than the recommended seven to eight hours per night stood out as the biggest contributor to faster brain ageing,” says Dove. “This was followed by having a late chronotype; in other words, being an ‘evening person’ or ‘night owl’.”
The primary reason why appears to be down to inflammation, albeit there are likely further factors at play. “For example, poor sleep can increase the risk of conditions like diabetes and cardiovascular disease that are themselves detrimental to brain health,” says Dove. “Another explanation centres on the glymphatic system. This is the brain's waste clearance system, which is mainly active during sleep. Poor sleep can disrupt this system, allowing harmful substances to build up in the brain.”
How can you track your sleep?
A limitation of the study is that the sleep data was self-reported, which was inevitable with such a large cohort. This does raise the question of how you can track your sleep effectively to ensure you keep your brain young.
Unfortunately, there’s no perfectly accurate method unless you hit the labs and have an EEG to measure brain activity. That said, sleep trackers like those from Whoop are deemed generally accurate to measure quantity of sleep, but not great for assessing duration in the different sleep stages. Arguably, a clearer insight is waking fresh. Achieve that and you’ve kipped well.
If not, Dove recommends keeping a regular sleep schedule (i.e. going to bed and wake up at a consistent time every day). “Also, limit caffeine and alcohol intake and screen use before bedtime and create a dark and quiet sleep environment.”
Or you could simply crack on with insufficient shuteye. A small percentage of people (fewer than 1% of the population) have a genetic mutation (DEC2 gene) that allows them to function normally on four to five hours of sleep each night.
Whether that explains historic outliers remains to be seen, but there are plenty of them. Leonardo da Vinci died in 1519 at the relatively healthy old age of 67. The renaissance man reportedly followed a polyphasic model of sleep where he napped for 20 to 30 minutes every four hours for two to three hours’ kip each day. Inventor Thomas Edison passed away in 1931 at 84 years old. The American believed sleep was a “criminal waste of time”. And then there’s Donald Trump, who sleeps for four to five hours…
“Ultimately, the take-home message of the study is that prioritising healthy sleep is important for maintaining brain health as we age,” Dove concludes.