Sleep need becomes fixed in our early 20s. Basically, once we've been through puberty and our teenage years. What happens as we get older is that our ability to get that sleep changes because we start losing some of the deep restorative sleep. So our sleep becomes lighter and less refreshing.
In men that happens around the time of 35 or so. In women it's around the age of 55. From the age of 35 men's sleep starts declining; it becomes less refreshing and because it's less deep we are also more liable to be woken up. So when you're 20 you might wake up needing to go for a pee – you do that and you get back into bed and you fall back to sleep. Around the age of 35 that starts becoming less and less easy to do. I'm 51. If I get up and go to the toilet I get back into bed and I do not instantly fall asleep – it takes a while.
"You need the same amount of sleep, you just find it more difficult to get it as you get older."
For women these changes generally occur around the age of 55. But of course with women there are numerous hormonal changes to their sleep. In their teens and twenties, and even thirties these days, there are pregnancies. In their forties and fifties there is the menopause – and that can have a significant affect on sleep. And if you then combine the menopause with having poor sleep anyway – your sleep becoming lighter – it's going to be difficult to get a good night's sleep. Or it becomes increasingly difficult to get a good night's sleep. So that's really the difference.
You need the same amount of sleep, you just find it more difficult to get it as you get older. The other thing is that even if you do get your required amount of sleep, you might not feel any benefit. When you're 20 you go to bed, you die for nine hours, you wake up and you feel absolutely brilliant and ready to take on the world. As you get older that doesn't happen. You sleep through the night, you wake up and you think, 'Was that it?' It is a change – a natural change.
There are also age-related changes that may cause problems with sleep. As men get older they put on a bit of weight and they might start snoring or develop sleep apnea. They might also need to get up to pee more frequently. So there are those natural changes that happen to you that will also disturb your sleep. And because your sleep is inherently lighter it's a combination that will make going to sleep worse.