Blue light before bedtime is renowned for making it harder to fall asleep - but blue light in the morning could be just what we need for a better night's rest
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Hello, and welcome back to Everyday Science.
Do you have any burning questions around science or health that you’ve always wanted answering? If so, send them to me. If I can’t answer them myself, I’ll interview an expert who can, for a new Ask Me Anything section in this newsletter.
Email me at clare.wilson@theipaper.com or contact me through Instagram or X (formerly Twitter), at @clarewilsonmed. I’m afraid I can’t take questions about your personal health, but anything else that’s science-ish is up for grabs.
Sleep insights
Back to this week’s newsletter. About a decade after they became popular, I have finally succumbed and got myself a fitness tracker.
I’ve long been sceptical about these wrist-worn devices as I’m convinced that for most people, overly focussing on our medical data is unnecessary and could even encourage hypochondria and health anxiety. I only bought the thing to motivate myself to swim faster at the pool.
Well, I am now being sucked into looking at my sleep statistics every morning. It is fascinating. And a recent small study that suggested a simple way to improve sleep has prompted me to start experimenting on myself.
Morning light
Most of us have probably heard by now that if you’re not getting enough sleep, it is best to avoid looking at our phones or watching TV in the evening, especially in the last hour or so before bedtime, because of their blue-tinged light.
The new research, however, has found that in the morning, exposure to blue light has the opposite effect, and helps people have a better night’s sleep the next night.
These effects happen because our sleepiness is influenced by our body clock or circadian rhythm. The body clock is governed by a physical structure inside the brain, which gets signals from light-detecting cells in the eye. This helps make sure that we are more alert and energetic in the daytime, but as night approaches, our metabolism slows and we become ready to sleep.
The eye cells are especially sensitive to shorter wavelengths of light, otherwise known as blue light.
This is why viewing screens in the evening wakes us up and can make it harder to nod off when we put down our phone. But the new study suggests we can also hack our body clocks, by deliberately exposing ourselves to blue light in the morning.
Researchers at the University of Surrey asked 36 older people who had poor sleep to sit in front of a table-top light box for two hours, either at the beginning or end of the day.
Blue light in the morning helped people to have less disturbed sleep, compared with a control condition, when the light boxes gave out pure white light, according to the study in the journal, GeroScience.
Such a finding has also been seen in laboratory studies, but it’s encouraging that it was also experienced by people using light boxes at home, showing it can be a real-world help, said chronobiologist Dr Daan van der Veen, who was involved in the research. “That’s the eye opener,” he said.
And people don’t need to buy special light boxes because natural daylight is not pure white, but has a high proportion of blue wavelengths, he said. So we can probably get the same effect just by spending time outdoors, or sitting next to a large window, ideally as soon as we wake up. “If you find the time to go out and have a walk every morning, even if it’s just half an hour, that would be beneficial,” said Dr van der Veen.
And there is nothing wrong with blue light from your phone in the morning either.
Professor Glen Jeffery, a neuroscientist at University College London, who wasn’t involved with the research, said it was significant that the approach helped with older people.
That’s because as we get older, the lenses inside our eyes tend to have build-up of proteins, which filter out more blue wavelengths of light. This might be one reason that older people have more sleep problems.
Heating up
Most of us are familiar with all the usual advice for getting better sleep, like winding down in the evening and avoiding caffeine and alcohol. I won’t list them all here, but you can see many such tips on the NHS website.
I’ve highlighted the blue light study because, in contrast, it suggests we should be changing something we do in the morning. Another less well known sleep hack also tries to manipulate circadian rhythms, by exploiting the fact that our body temperature is about 1°C higher in the daytime than when we sleep.
A man reads a newspaper in the bath
Sleep hacking? (Photo: Peter Dazeley//Getty Images/The Image Bank RF)
The idea is that if we can artificially heat ourselves up in the evening, the ensuing fall in body temperature will encourage the body to switch into bedtime mode. Sure enough, some small studies suggest that we sleep better at night if we can raise our body temperature, by having a warm bath or shower about an hour before bedtime. A bath only needs to be about 10 minutes long.
It isn’t the rise in temperature that makes us tired, it is the fall in temperature afterwards. This is why it is also recommended we keep our bedrooms relatively cool, at about 18°C.
Working out
If you’re not keen on soaking in a hot bath, there is another way to raise your core body temperature – and that is exercise. That’s because contracting muscles generate heat as a byproduct, which is circulated round the body by the bloodstream.
“The hotter the body is during the day, the more likely it is to fall to sleep and stay asleep,” Professor Adrian Williams, a sleep physician at King’s College London, said on the website for the NHS meditation app, Headspace.
But when you exercise is crucial. Doing it in the morning is too far away from bedtime to have an effect on sleep. But if you exercise right before bedtime, it will raise levels of the fight-or-flight hormone, adrenaline, which makes you more alert.
Therefore, if improved sleep is your goal, exercising between 4pm and 7pm is the sweet spot, said Professor Williams. “Timing is everything,” he said.
I’ve also written
The official NHS diet advice for people with type 2 diabetes may be in need of updating. People are currently told to eat a low-fat high-carb diet, but growing research suggests that some people with diabetes see their blood sugar levels and general health improve if they eat a low-carb, high-fat diet – the opposite approach.
I’ve been watching
I’ve only just got round to watching the Martin Scorsese thriller, Shutter Island, a gripping exploration of paranoia and madness, set in a 1950s institution for the criminally insane, in the US.