The Science of Sleep

Liverpool-born, California-based sleep scientist and the author of New York Times bestseller ‘Why We Sleep: The New Science of Sleep and Dreams’, Dr. Matthew Walker speaks to YM Liverpool about his home city, the true value of a good night’s shut-eye and the one question he still wants to find the answer to.

Interview by Lawrence Saunders

Which part of Liverpool are you from? Do you ever come back to visit?

I was born in Alder Hey Children’s Hospital and grew up in Gateacre. Later we moved out to Childwall for a few years. Liverpool is where home is and it’s where most of my family remains.

I come back to visit probably once or twice a year, mainly to see family and friends. I am a Red so I watch as many games as I can – so long as it’s not too early a kick-off because here in California we are essentially eight hours behind.

The games are usually on around seven or eight o’clock in the morning and I give myself a non-negotiable eight hours to sleep. I’m a 10pm to 6.30am kind of person right now so it actually works out really well – get up, make a cup of tea and then watch the Reds!

That’s how I stay engaged with Liverpool and it holds an incredibly special place in my heart. I love the city, how down to earth people are and their sense of humour. I love how Liverpool is reinvigorating itself too.

A couple of years ago I came down the waterfront to see how that‘s changed and I think it’s just great. I love the fact that the city is getting that type of investment attention, it well deserves it.

When did you first decide sleep, and the science of sleep, was a field you wanted to investigate further and specialise in?

I was doing my PhD on dementia patients with the Medical Research Council in London. I was studying a group of patients in Newcastle and early on I was trying to diagnose which type of dementia they had. Was it Alzheimer’s disease? Parkinson’s disease? Vascular dementia?

I was using their brainwaves to see if I could find the difference and I failed miserably for two years. I’d go home to the doctor’s residence each night with all of these journals and I’d sit and read.

One weekend it became clear that for some of these disorders, the parts of the brain that were being eaten away were actually sleep centres and in other disorders they weren’t. So I realised I was measuring my patients at the wrong time, which was when they were awake, and I should have been measuring sleep.

I applied for a grant. started a sleep centre and discovered some great results. That was it – I just fell in love with this thing called sleep, why we did it, and what was the consequence to my patients if they weren’t getting sleep or their sleep was desperately disrupted. Was it not just a symptom of dementia but the cause?

How long should a person sleep each night?

The average amount that we recommend is eight hours for adults. The range [adults get] is somewhere between seven to nine hours.

Once you get below seven hours sleep we can measure objective impairments in your brain and your body. I would say that the number of people who can survive on seven hours of sleep or less without showing some kind of detriment, rounded to a whole number and expressed as a percentage of the population, is zero.

Why is it so important to get that specific amount of sleep?

Every single physiological system in your body and every operation of your mind is wonderfully enhanced by way of sleep when you get it, and demonstrably impaired when you don’t get enough.

The reason that’s critical is because every disease that is killing us in the developed world now has significant, and many of them causal links, to a lack of sleep.

Those associations with a lack of sleep range from cardio vascular disease. obesity, diabetes, strokes, anxiety, depression, suicidality, cancer and finally, dementia and Alzheimer’s disease.

In fact, a lack of sleep seems to be one of the most significant lifestyle factors which determines whether you will develop Alzheimer’s.

Do you think the general public is still largely unaware of how important sleep is both to their mental and physical health?

I think so. It’s doing better but sleep has been the neglected stepsister in the health conversation of today. We’ve heard 21 lot about diet and exercise but too little about sleep. It’s not to say those things aren‘t important, they are important, but the reason I find that peculiar is because sleep is not the third pillar of good health – sleep is the foundation on which [diet and exercise] sit.

I don’t want to argue that sleep is more important [than diet and exercise], but I could make that argument because if I deprive you of food for 24 hours, or exercise for 24 hours, or a night of sleep within that 24 hour period, the amount of impairment you would suffer by way of a lack of sleep is far greater in magnitude than either of those two alone. So sleep truly is essential.

What is the one question about sleep you still haven’t found the answer to?

That’s a great question.

Every living species that we’ve studied to date, sleeps, which tells us that sleep probably emerged with life itself on this planet and then fought its way heroically through every step along the evolutionary path.

But the amount of sleep, and the way animals sleep, is so dramatically different. Elephants, for example, may sleep only about four hours, whereas us humans need about eight hours. The little brown bat is the rock star of sleep – it sleeps up to 19 hours a day.

We just don’t understand why it is that different species need different amounts of sleep. People have come at this from every possible angle that you could imagine – is it size? It is metabolic rate? Is it food? Is it prey versus predator? Is it their location on the planet? None of these are a straight line prediction, so I think that holds the clue to something fundamental about sleep.

It tells us perhaps why we need the specific amount we do and why we can’t get away with less, and why we don’t need more.

Dr. Matthew Walker is professor of neuroscience and psychology at the University of California, Berkeley, USA.