Juan Antonio Madrid

Chronobiologist and professor of physiology

"Sleep deprivation has an incredible influence on learning and performance"

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Spaniards have two big sleeping problems. One is insomnia, problems falling or staying asleep. And the other problem is phase delay, which involves problems going to sleep at night and getting up in the morning. The science I do, which is chronobiology, deals with these problems. And I'm convinced that it's going to help us understand them. Chronobiologists are a group of scientists, we don't have anything to do with horoscopes, biorhythms, astrology, we study biological rhythms. What is a rhythm? Well, a rhythm is any aspect of the biology, the biochemistry, the behavior of a person or an animal that changes over time. But that changes in a predictable way. That is, it changes cyclically every year, every month or every day. So we're talking about different categories of rhythms. The 24-hour rhythm is called “circadian.” It's the one that has been studied the most, but it's not the only one. For example, the migration of birds, the flowering of many species… These rhythms all have a one-year period. And there are rhythms that have a daily period. For example, sleep. These are the circadian rhythms. And what drives these rhythms? Well, a clock. In fact, we have many clocks in our bodies.

When we speak of broken clocks, we use a scientific term called “chronodisruption.” This is an alteration of the circadian rhythm, the system that controls time, and it's linked to many pathologies. I don't want to alarm anyone, but chronodisruption is involved with, for example, cognitive and memory decline, accelerated aging, with some types of cancers: breast, colorectal, prostate. With insomnia, obviously, with immunodepression, with reproductive disorders, with another very important aspect: emotional disorders, depression. With metabolic syndrome: obesity, diabetes. That is, we have an entire set of pathologies that get worse when our biological clocks are off. Mind you, I'm not saying you're going to get all these things if your clock is off, but they get worse. And insomnia is a sign that the clock isn't working right. So when someone has insomnia, they almost always think: “OK, so what do I have to take? What pills do I have to take? What's the doctor going to give me?” But I think that the first thing you should do is find out why you have insomnia, what's causing it, what's the source. Because if not, what you're doing is eliminating a symptom, taking a drug that turns off that light that's turning on and warning you that something's not right. And it's always going to be there. So insomnia has to be treated using a comprehensive approach.

"There are ways to evaluate the sleep education our kids are getting, and the vast majority of them would fail"

Chronogiologists study life as a whole. Your days and your nights. Is something predisposing you to insomnia? Maybe not, the cause could be something internal in your neurons, in your sleep center. But generally, an external cause has to be considered. We try to figure out why sleep problems and chronobiological disorders are on the rise. And we come to a very simple conclusion, one that can also be measured, and it's this. Imagine how you would live if you had three different clocks in your brain. Clocks from Tokyo, London, and New York. And your physical body had to combine those time zones. Well that's what we're doing. We have a clock, an internal and a biological clock that's telling you: "Hey, no, I'd rather sleep between two and ten in the morning. That's my biological time slot." We have a second clock, based on artificial light, that we can use to generate the light-dark cycle we want. It's no longer the sun that generates it. But we also have a third clock, a social clock. The social clock is: When can I sleep well, sleep what I need to sleep, if I have to go into work at eight in the morning and I need an hour and a half to go to work? So I have to get up at 6:30. When would I have to go to bed to adhere to this schedule? So when you notice the impossibility of making it all fit, you realize where the problem lies. The problem oftentimes is that your internal and social clocks don't match. And those imbalances are measured in hours. The more hours they're out of phase, the worse you are. For example, if you have a problem with insomnia and we see that it's not a problem due to the three clocks, to inconsistencies with the three clocks, we rule out the chronobiological part and look elsewhere.

What's the purpose of sleep? We know part of its purpose, but not all. Just four years ago, a primordial function of sleep was discovered. Sleep cleans the brain of toxic substances that build up during the day. If you'd get enough sleep, if you don't sleep soundly, those deposits that can later cause Alzheimer's, Parkinson's or cognitive impairment don't get flushed out well and they build up and damage your neurons. So we need to sleep. Even if we don't feel the need in the early stages of life, we have to get enough sleep and sleep soundly.

Sleep has a profound effect on learning and performance. We don't know the figures, but much of the academic failure we experience could be attributed to not enough sleep. It's a very generalized problem. I don't think we realize, as a society, how important this is. We who are involved in teaching see a lot of dazed faces at nine in the morning. And by noon, there's no way to shut them up. So we have a phase delay problem as young people go to bed later and later. And since they have to get up early for school, they're deprived of sleep.

And what does sleep deprivation do to performance? Well, for example, it increases reaction times, the speed at which we become aware of any type of stimulus. What kids often do is they disconnect. They get drowsy and since on top of that, learning tends to be very passive, since they're receiving what someone else is actively explaining, they simply disconnect and think about something else. And that's easy to understand, naturally. The sleep center that determines their biological clock is still at six or seven in the morning. You woke them up halfway through their sleep. And you're taking them to school and passively sitting them down to receive information. What do you expect?

Juan Antonio Madrid is a Professor of Physiology and specialized in chronobiology at the Pierre and Marie Curie University in Paris. He is also the director of the Chronobiology Laboratory (Cronolab) at the University of Murcia, which is part of CIBERFES, the Network of Biomedical Research Centers on Frailty and Healthy Aging. We have before us one of the greatest experts in the field of circadian rhythms, an authority on unraveling the secrets of sleep, and its importance to health and learning.