Lluís de Lecea: "Sleeping well is as important as exercising"

BarcelonaThe writer Vladimir Nabokov was horrified at having to forcibly lose consciousness eight hours every day. Without sleep, however, he would not have written anything resembling a masterpiece such as Pale Fire, because his brain would not have been capable of it. Sleep is essential for the proper functioning of the brain. At the same time, the brain regulates when we fall asleep and when we wake up by means of a hormone called hypocretin. Lluís de Lecea, professor of psychiatry and behavioural sciences at Stanford University, is one of the scientists who discovered it.

What is sleep from a biological point of view?

— It's a very complicated choreography. The brain doesn't shut down but there is a reorganization of the flow of information that circulates to make it more efficient during wakefulness. In the animal kingdom there are many strategies of the nervous system and they all converge in the sleep-wake cycle. Even sponges and hydras, which are very primitive animals and don't really have brains, have cycles of activity and rest. So we suspect that sleep is really essential for biological activity.

Beyond animals, are there similar cycles in other living beings, such as unicellular beings?

— Unicellular beings have metabolic cycles that, in bacteria and algae, are dictated by the availability of resources, but they are not sleep cycles. That's why we think that sleep evolves from these metabolic cycles.

In 1998 you discovered hypocretin, what is the role of this hormone in sleep?

— In vertebrates and mammals, we know that there are diseases such as narcolepsy [extreme daytime sleepiness] that are caused by the deficiency of a group of neurons that produce this hormone. Without it, the sleep-wake cycle is disrupted. Hypocretin is essential for a complete and well-structured sleep cycle because it integrates circuits that are essential for the stability of sleep. It integrates, for example, the metabolism, which must be regulated in a certain way during sleep and in another way during wakefulness. And it also integrates emotions.

Are emotions important in sleep?

— They are, and very much so. In the case of animals, for example, positive emotions that release dopamine and which occur when food or a reproductive opportunity is available prevent sleep. Anything that activates reward mechanisms does. Negative emotions, which in nature are summed up as stress, do too. If you have a predator on your tail, it's not a good idea to go to sleep, right? Well, all these variables are integrated in the hypothalamus and it's the hypocretin that tells you when it's time to sleep or to wake up.

There is a lot of talk about how many hours you should sleep and in this sense the idea of the sleep quantum is very interesting. What is it?

— It is the minimum unit of continuous sleep that is necessary for sleep to function properly. It seems very obvious that in order to have a full function of sleep we need to sleep a minimum of 6 or 7 hours, and if we don't we are knackered. Mice, for example, have a 15-minute sleep cycle. They sleep for 15-minute periods alternating with waking moments. In their natural ecosystem, if they slept 7 hours, they would be extinct by now. We have seen that in mice the quantum of sleep is about 2 minutes, and that in humans it could be about 4 hours.

Does this mean that with 4 hours of sleep we should have enough?

— These 4 hours would be the minimum, not the recommended 8 hours, that is, two of these units. This, however, is still an extrapolation. We have demonstrated it in mice, but not yet in humans.

Is it true that in the middle of the day the body experiences a drop in metabolic rate that coincides with the time of the nap?

— Yes, in fact, there are very interesting studies in communities that do not have artificial light, which have been done in Amazonia, in which it has been seen that it is completely natural that after midday there is a drop in metabolic activity that facilitates the siesta.

Insomnia is one of the most common sleep disorders. Why does it occur?

— There are two types of insomnia. In the first, the typical patient complains that he/she does not sleep and is fatigued during the day, but when he/she goes to a consultation and undergoes a complete sleep study, nothing is detected. The patient sleeps the right amount of sleep and the sleep structure is normal. But he complains, and it is not an invention. He complains because he does not sleep well. Half of the patients are like that. These patients respond very well to cognitive behavioral therapy, which is based on good sleep hygiene.

What is sleep hygiene?

— Many times, without wanting to, we have a very inefficient sleep and our brain tries to adapt to these conditions that are not optimal. The brain's adaptation makes you end up sleeping, but you have the perception that you are not sleeping well. This is fixed by facilitating the sleep cycle in a more natural way. A very typical example of bad hygiene is the person who is a bit stressed, can't sleep and before going to sleep goes to the computer to try to relax, ends up checking email and that stresses him even more. In this case, in addition, the light from the computer is telling the brain that it is daytime. All of this is a disaster from the point of view of facilitating sleep conditions. Many people are not aware of this and this type of therapy helps to facilitate the conditions for sleep.

What is the other type of insomnia?

— This is a neurological and sleep architecture problem that is often difficult to diagnose. It can be treated with medication, but it's often a band-aid and doesn't fix the underlying problem, which is very serious. A lot more work has to be done to figure out what the problem is and why the sleep architecture is disturbed. An extension of this subtype is sleep apnea, which many people do not know they have and that leads to a very inefficient sleep, becaus the quantum is not achieved. There are also other neurological diseases like Parkinson's, which affect the sleep architecture very significantly and have another type of treatment.

Do sleep problems affect many people?

— It varies quite a lot between countries, but in the United States, for example, 30% of the adult population has suffered or will suffer from sleep problems and that is obviously a very serious public health problem.

Can these problems be solved through education?

— Education is absolutely fundamental to prevent and cure them. For the last 30 or 40 years we have been taught that exercise is important and everyone is aware of this. Sleeping well is just as important. There is, for example, this preparatory phase of sleep which is very important in animals and that is to build a safe place to sleep. All animals do this every night. If you destroy an animal's bed, it compulsively makes another one because it has it engraved in its brain that a bed must be made before sleeping. If, in our case, we have a messy room, the brain processes it in some way and understands that it is not a safe place to rest, so it is on alert and does not rest well. Now we are deciphering neural processes that do just that, tell the rest of the brain when it is a good situation to sleep.