Sleep. It’s amazing how this non-functional state, where we’re out to the world and we’re open to predation, or at least historically we have been, is so important. In fact, not going to sleep will harm your health quicker than anything else. Staying awake for the longest has been taken out of the Guinness World Records now, because it’s so dangerous. Going without sleep for three or four days can, and will, kill you. It will kill animals as well. It’s so vital for our health.
The biology and the architecture of sleep
There are a few basic principles that are worth thinking about here. The first is what we call sleep pressure. There are two chemicals involved. One is a hormone called melatonin. When you’re awake during the day and you’re exposed to bright light, sunlight, which is high in blue wavelength light, melatonin is suppressed down. As it gets near dusk, you’ll start to secrete melatonin and you become more sleepy. Obviously, the way to maximise that is to be out in the bright light during the day and avoid anything that emits blue light during the evenings. Unfortunately, LED lights and LED screens put out blue light in a higher proportion than the sun. Not brighter than the sun, but in a higher proportion. So they’re clearly things to avoid.
“It’s important to sleep. It’s important to a healthy life. It’s important to a long life. It’s important to immune function.”
There’s also a second pressure, through a neurotransmitter, called adenosine. It starts out low at the beginning of the day, and is sneaking up during the day. Coffee pushes it down, which is one of the reasons that caffeine close to bedtime for most of us is a bad idea, but also, falling asleep in your arm chair while you’re watching TV at night squashes that adenosine down. If one of the main pressures for sleep isn’t there anymore, you’ll have a bad night’s sleep. Adenosine and melatonin are the sleep pressures.
What are the recommendations?
In general, seven or eight hours of sleep is optimal, but it might be a bit more for some of you. If you think that you’re getting away with less, you’re probably not doing as well as you could do for your human potential. I suggest to give yourself an 8 hour sleep opportunity, a window where you’re organised enough to get eight hours. For the best biological outcomes of sleep, as it starts to get dark, start to get yourself organised for sleep. An hour or two after that, go to sleep, and when it gets light, it’s time to get up. That’s optimal. People have other rhythms, but I think for most of us, that’s the way it should go.
What happens when you’re sleeping?
You’ve heard of the circadian rhythm, but there’s also the repeated cycle of the ultradian rhythm – peaks and troughs of brain activity is part of the normal sleep architecture. If you flatline with no brain activity through sleep – well, you’d be unconscious – you won’t get all the gains. If you booze yourself to sleep, if you drag yourself to sleep with sleeping tablets, or if you keep waking up, because you’re a snorer or sleeping near snorers, then you’re not getting that architecture of ‘deep sleep, dream sleep, deep sleep, dream sleep’. The intensity of the dream sleep increases during the night, and the intensity of the deep sleep is highest at the start of the night.
What happens in these two different phases and why are they so crucial? A Danish scientist discovered in 2014 that there is a whole system inside of the brain called the glymphatic system. You’ve probably heard of the lymphatic system in the body. In the brain there is the glymphatic system, and it’s really a cleaning cycle. The flow through the glymphatic system goes up threefold during deep sleep.
“Deep sleep is crucial for ‘uninflaming’ your brain.”
You can think about perhaps going to bed with a bit of inflammation, mild brain damage, from being awake that day. The repair and rejuvenation of that is in deep sleep. If you go to bed too late, you won’t make up for that loss of deep sleep. So going to bed an hour or two after it gets dark gives you a chance to get the most out of the deep sleep and clear the waste away. Interestingly, deep sleep clears out tau, beta-amyloid and other products implicated in the formation of Alzheimer’s disease, so it is an important part of Alzheimer’s prevention.
Dream sleep
We know that dream sleep is a very active phase for the brain, and it’s crucial for mental health, cognition, improved cognition and problem solving. You could think about it as, during the day you accumulate post it notes through the brain, and during the dream sleep at night you start to move those post it notes around the brain and put them in the right place. If you’re waking up far too early in the morning, or not getting that quality, good night’s sleep of seven or eight hours, you won’t get the best quality dream sleep, because it happens around that six, seven hour range. That’s where the magic really happens for the highest intensity dream sleep.
How do you get the most out of your sleep?
Here are my top three tips:
- Go bed tired – physically tired
- Avoid blue wavelength light, especially just before bed
Get off your device. Start reading a book – my best recommendation is Matthew Walker’s Why We Sleep. It is the best read I’ve had in the last year.
- Get hot, then get cold
If you can get blood going to your legs and arms, and then it gets drained away back into the central organs, that enhances melatonin. So a hot bath before bed is a good idea.
Our dog Bluey keeps us in a routine. He’s well-trained. Well, he may have trained me well. He gets up at first light every morning. He comes and knocks on my arm and says, “I need feeding”, and then I wake Louise up and she goes and feeds him. No, not really, we take turns.
Recommended reading
Matthew Walker’s Why We Sleep (2018)
Podcast: Peter Attia, series on sleep
More on sleep by Prof Grant Schofield: