1. Your head explodes…

Don’t panic – it won’t actually blow up, but there is such a thing as Exploding Head Syndrome. That’s when you hear loud noises – like an explosion – just as you’re dozing off or waking up.

‘The exact cause of exploding head isn’t really known, but you might hear these types of noises more when you’re really tired or under stress,’ Dr Gilbert says.

Some research shows it might have something to do with ear problems and not getting enough calcium.

‘While harmless, it can be distressing for the person hearing these noises and their heart rate can change dramatically,’ he says.

2. Our reflexes are out of whack

Those quick, involuntary movements, like suddenly kicking your legs or the sensation that you’re falling, are called ‘hypnic jerks’. This happens when the body and brain shift too quickly from being awake to asleep.

‘Sometimes this shift doesn’t progress as smoothly and we get the equivalent of when a doctor hits our knee with a mallet to test our reflexes,’ Dr Gilbert says.

‘Another theory is it’s connected to our evolutionary journey from apes, as they’d too instinctively jerk to catch hold of a branch before falling asleep.’

3. Some sleep with their eyes open

You’ve heard the saying: ‘sleep with one eye open’. Sounds creepy, but people actually can get some shut eye without locking their lids.

‘Sleep is actually a transition from light to deep stages. You can technically be asleep but still have your eyes open,’ Dr Gilbert says.

‘Some people who sleep walk obviously appear awake and wide-eyed and might even respond to instructions, but we’ve conducted studies where brain wave activity clearly shows they’re not awake,’ he adds.

4. We really do need our beauty sleep

While it doesn’t have the same ring to it, it’s best described as ‘growth’ sleep rather than beauty sleep.

When we’re in a deep slumber, the body produces HGH – a hormone that helps us grow.

‘There’s less of this hormone as we get older and, of course, you can’t grow taller than your predetermined, genetic height. However, in older people, the cartilage separating each vertebrae in the spine gets compressed by gravity, so they’re a bit shorter each night but, in the morning, they can be about 1cm taller,’ Dr Gilbert says.

5. And, here’s how many spiders we actually eat…

They say it’s best not to eat right before bed, but what about during our sleep?

While online rumours have it that we eat about eight spiders in our sleep each year, some researchers say it’s more like eight in a lifetime.

‘It really is all anecdotal evidence. Unless I see it with my own eyes or on video of a patient during their sleep, I won’t be convinced. If it is true, these creepy crawlies certainly haven’t done any of us much harm,’ Dr Gilbert says.