‘If you feel knackered, you’re not getting enough quality sleep and probably need to do something about it’
Like eating our greens, we all know sleep is good for us. But it’s not quite as straightforward as just getting in our eight hours, says Dr Michael Mosley. We caught up with him to learn more about what really goes on in our brains at night and why sleep quality is just as important as quantity.
Words: Chantelle Pattemore
What happens to our brains during sleep and why is shut-eye so important?
There are four stages of sleep. Stage one is the light sleep you drift into where you’re easily woken. Then you go into a slightly deeper sleep, and then into deep sleep – normally within an hour of drifting off. That’s a really critical part of your night because, during deep sleep, a lot of the memories accumulated during the day get shifted from short-term storage into long-term storage. So, if you don’t get enough deep sleep, it affects your memory.
The other really remarkable thing which happens during deep sleep is that an area in your brain called the glymphatic system opens up. These are like channels in your brain where cerebrospinal fluid – the stuff which sort of swishes around in the brain – washes away toxins that have accumulated during the day. Deep sleep is really important for getting rid of things like tau proteins, which have been linked to increased risk of dementia.
But there’s another phase of sleep, which is rapid eye movement (REM) sleep. During that period a lot of your emotional regulation gets sorted out, and that’s when you have intense dreams. If you don’t get enough REM sleep, you tend to wake up feeling agitated and disturbed – so emotional regulation seems to be a hugely important part of that stage of sleep.
Sleep is clearly important for our brains. What about the rest of the body?
It affects your appetite, so when people sleep badly, they tend to crave more sugary junk food the next day; on average about 250-300 calories more. Lack of sleep is also very bad for your heart; we know that it increases your risk of heart disease and type 2 diabetes. It also affects your sex drive. That’s just hitting some of the highlights. Beyond that, lack of sleep can also affect your microbiome, your gut. Almost every system in your body.
How much sleep do we need each night? And can we get too much sleep?
On average, people say between six and eight hours, but that usually depends on individuals. There are some people who get by fine on five hours; some people need nine ho
