What dogs dream about? And other sleep questions and tips
We sleep for a wide range of brain and body benefits. According to the latest research, there isn't a system in your brain or body which isn't enhanced when you get sleep, or impaired when you don't get enough.
Matthew Walker is a best-selling author and professor of neuroscience and psychology at the University of California.
He answered questions from BBC Radio 5 Live listeners about sleep-friendly routines, what to do if you’re a shift worker as well as why it’s helpful to avoid alcohol and caffeine before bedtime.
Why do dogs run when they sleep?
"When you go into a deep dream sleep, also known as Rapid Eye Movement (REM) sleep, your brain paralyses to protect your body and so that you don't act out your dreams.
"But as you get older, that part of the brain that locks your body starts to fail. So people will start to act out their dreams.
"We also see it in animals, which is really the only sign to signal that animals dream as humans do."
What is the connection between lack of sleep and mental health?
"I've done a lot of work in this area and research suggests that insufficient sleep is not just a symptom or consequence of a mental illness, but may be a triggering cause of many of these mental health problems including depression and anxiety."
Can you repair the damage after years poor sleep?
"Yes and no.
"Sleep is not like the bank – you can't accumulate a debt and repay it at a later point in time.
"It's an all-or-nothing event in that sense, so the damage done with insufficient sleep has been done.
"However, it’s never too late to start sleeping better."
What's the cut off time for caffeine?
"You need to abstain from caffeine 14 hours before you want to go to bed.
"If you need caffeine to strategically wake up, that's okay, but be a bit mindful that you're not medicating your state of chronic sleep deprivation."
I keep waking up at 3am and can't get back to sleep - how do I break the habit?
"Meditation could be an option to try and calm your nervous system down and go back to sleep. There are plenty of helpful books and apps which offer guidance on that.
"The other tip would be if you've been lying there for more than 15 minutes, get out and bed and go to another room. Make sure the room is dimly lit and only return to bed when you're sleepy. That way your brain learns that being in bed is about being asleep, not being awake.
"You wouldn't sit at the dinner table waiting to be hungry, so why go to bed and wait to be sleepy?"
What about bizarre dreams?
"What we think is that one of the functions of dreaming is to take all the information you've learned and integrate it with your back catalogue of knowledge so that you make up with a web of associations in your mind.
"It's like memory pinball where you take all the new memories, colliding them to see if they fit. It's almost as though your brain is trying to make links.
"It's like a Google search gone wrong, where you accidentally go to page 20 which is totally irrelevant. It's like problem solving or informational alchemy which is solving problems you can't do when you're awake."