As he poses for photographs in the lobby of the Riu Plaza España Hotel in Madrid, where he went to give a lecture as part of the 20th International Congress on Anti-Aging Medicine and Medical Aesthetics, Doctor Juan Antonio Madrid, 65, realizes that he happens to be in the Spanish capital just as his retirement is becoming effective. But judging by the casual way he mentions it, as well as his physical appearance and the energy he radiates, it does not seem as if the milestone will put a stop to his research and dissemination work.
The professor of physiology, director of the Chronobiology and Sleep Laboratory of the University of Murcia and one of the world’s leading experts in chronobiology, confirms this impression. He says he is planning to continue his research work (“at a different pace”) and share the knowledge he has gathered after more than four decades of study. Part of this knowledge can be found in a recently published book: Cronobiología: una guía para descubrir tu reloj biológico (or Chronobiology: a guide to discovering your biological clock), where he reflects on the importance of adjusting our internal clocks to the cycles of nature, something almost impossible in a world dominated by artificial light and screens.
Question. At the next congress of the Spanish Sleep Society you will give a talk on sleep in the Middle Ages. People talk a lot about biphasic sleep these days.
Answer. In the Chronobiology and Sleep Laboratory of the University of Murcia we have monitored 9,800 patients from whom we obtain data on their exposure to light, their activity and their sleep, seven days a week. After analyzing their sleep, we have seen that a significant percentage of individuals wake up between 3am and 4am. That is the moment in which a great awakening used to take place during the Middle Ages. In those times of biphasic sleep, people went to bed early, one or two hours after sunset, and had a waking period of one to three hours during the early morning, which they dedicated to prayer, reading, having sex or telling stories. Then they had a second sleep. When spring came, the two periods of sleep started to get close, until they almost merged in summer, which is when the nap appeared. It was a much more dynamic sleep than ours, modulated according to the seasonal change.
Q. It used to be much more coordinated with our biological rhythms.
A. Indeed. Sleep start and end times were coordinated without relying on a specific hour. Time was only kept in the monasteries. The rest of society operated with sunrise and sunset. That was what controlled the rhythm of work and rest.
Sleep is like a huge workshop where all the cells of our body are repaired
Q. We are talking about a world without artificial and electric light. You speak of the “dark side of the light.”
A. Light is a wonderful invention. I don’t want it to seem like I’m against artificial light. What I am against is its misuse. We should observe a minimum of eight to 10 hours of darkness in our homes. Or, at least, two hours before sleep, lower the intensity of the light and set a warmer tone to respect the internal production of melatonin. We also shouldn’t brighten excessively the public spaces in the streets. First of all, because it represents an economic expense. Second, because this pollution affects the chronobiological clocks of animal and plant species in a way that we cannot even imagine. And thirdly, because it affects human health. There are published epidemiological studies that show that the more we light up a city, the more incidence there is of certain types of cancer, such as prostate, breast or colorectal.
P. Are there estimates of how many hours of sleep we may have lost since the generalization of artificial light?
A. In just a century and a half we have lost between 60 and 90 minutes of sleep a day. I started studying this subject 35 years ago, when we still didn’t have personal computers, tablets and smartphones. As these new technologies have become generalized, we have witnessed a progressive drop in sleep time. The general average is close to seven hours, but if we only consider work days, then it is around six and a half hours. We live with a chronic sleep deficit.
Q. Are we a chronodisruptive society?
A. Yes, our society’s way of life encourages chronodisruption, a sustained alteration of biological rhythms. Excessive light at night, work shifts, a sedentary lifestyle, the use of electronic screens before bed and the work and leisure schedules don’t exactly help us maintain proper sleep rhythms.
Q. How does this lack of coordination between our biological and our vital rhythms impact our health?
A. Chronodisruption increases the incidence of many diseases in people with predispositions. And in those who already have them, this lack of coordination accelerates and aggravates them. Among other things, chronodisruption is related to an affectation of the immune system and to reproductive alterations, in addition to an increase in sleep disorders, cognitive disorders, affective disorders, cardiovascular diseases, some types of cancer, accelerated aging and disorders like diabetes, metabolic syndrome or obesity.
From the point of view of health, sleeping is the most revolutionary act we can do
Q. You explain in your book that writers like Miguel de Cervantes saw benefits in this apparently “wasted time” that is sleep. In addition to all the time and light difficulties, could that be happening to us as a society now? Do we tend to see sleep as wasted time?
A. Certainly. And every decade we subtract more and more minutes, to produce and consume more. There are even courses that teach how to sleep less, be more productive and feel good! Personally, I don’t see the point of this modern trend of wanting to sleep less, because sleep is like a huge workshop where all the cells of our body are repaired. And the mechanics need to take their time in that shop. We cannot repair in four hours what we wore out during the other 20.
Q. And yet, we always have the words “tired” and “exhausted” on our lips.
A. The thing is that, in some circles, saying you have hardly slept at all is even considered a positive trait. On the other hand, those who sleep the necessary hours are immediately branded as lazy. On a professional level, being always active is valued. It’s almost a matter of status. We have to change that perception. Now, luckily, it seems that there are movements that are beginning to alert us that something is wrong. For example, in the Great Resignation that is taking place in the United States, a lack of rest is very likely at the root of the problem.
Q. Scientific evidence has already confirmed that sleep is a pillar of health.
A. People complain of sleeping poorly, but they don’t associate it with illness. That is their mistake. Sleep is as important as diet or physical exercise – perhaps even more, because we can go without eating for several days, but not without sleeping. But it is hard for sleep to be considered a pillar of health in this competitive society that focuses everything on producing and consuming.
Q. Is capitalism taking away our sleep?
A. Capitalism has us dead tired. Everyone needs to know how much they need to sleep in order to be well. And stick to it. Sleep cannot be the last thing we spend our time on until we have managed to finish every other task. On the contrary, it should be a priority in our lives. We have to establish some hours and be disciplined, be brave in that sense. From the point of view of health, sleeping is the most revolutionary act we can do.