As he poses for photos in the lobby of the Hotel Riu Plaza España, in Madrid, where he went to give a lecture as part of the XX International Congress of 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 becomes effective. However, judging by the way he mentions it – with little more than a mumble – as well as his physical appearance and the energy he exudes, it doesn’t look like the milestone will put an end to his research and dissemination work.
The professor of physiology, director of the Laboratory of Chronobiology and Sleep at the University of Murcia and one of the world’s leading experts in chronobiology, confirms this. He plans to continue his research (“at a different pace”) and share the knowledge he has accumulated after more than four decades of study. Some of this knowledge can be found in a recently published book: Cronobiología: una guía para descubrir tu reloj biológico (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 lecture on sleep in the Middle Ages. We talk a lot about biphasic sleep these days.
Answer. In the Laboratory of Chronobiology and Sleep of the University of Murcia, we have followed 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 found that a significant percentage of individuals wake up between 3:00 a.m. and 4:00 a.m. It was at this time that a great revival occurred in the Middle Ages. In these times of biphasic sleep, people went to bed early, one or two hours after sunset, and had an awake period of one to three hours in the early morning, which they devoted to prayer, reading, sex or storytelling. Then they had a second sleep. When spring arrived, the two periods of sleep began to come together, until they almost merged in summer, when the siesta appeared. It was a much more dynamic sleep than ours, modulated according to the change of season.
Q. Before, it was much more coordinated with our biological rhythms.
A. Indeed. Sleep start and end times were coordinated without depending on a specific time. Time was kept only in monasteries. The rest of the company operated with sunrise and sunset. It was what controlled the rhythm of work and rest.
Q. We are talking about a world without artificial and electric light. You talk about the “dark side of the light”.
A. Light is a wonderful invention. I don’t want people to feel 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. Nor should public spaces in the streets be over-lit. Firstly because it represents an economic expense. Second, because this pollution affects the chronobiological clocks of animal and plant species in ways we cannot even imagine. And third, because it affects human health. There are published epidemiological studies that show that the more light a city receives, the greater the incidence of certain types of cancer, such as prostate, breast or colorectal cancer.
P. Are there any estimates of the number of 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 per day. I started studying this subject 35 years ago, when we didn’t yet have personal computers, tablets and smartphones. As these new technologies have become widespread, we have seen a gradual decline in sleep time. The general average is close to seven hours, but if we only consider working days, 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 chronoperturbation, a sustained alteration of biological rhythms. Excessive light at night, shifts, being sedentary, using electronic screens before bedtime, and work and leisure schedules don’t exactly help us maintain a good sleep pattern.
Q. How does this lack of coordination between our biological rhythms and our vital rhythms impact our health?
A. Chronoperturbation increases the incidence of many diseases in susceptible individuals. And in those who already have them, this lack of coordination accelerates and aggravates them. Among other things, chronoperturbation is linked to an impairment of the immune system and alterations in reproduction, in addition to an increase in sleep disorders, cognitive disorders, affective disorders, cardiovascular diseases, certain types of cancer, accelerated aging and disorders such as diabetes, metabolic syndrome or obesity.
Q. You explain in your book that writers, like Cervantes, could see the benefits of this “apparently wasted time” that is sleep. On top of all the hardships of time and light, could this happen to us as a society now? Do we tend to view sleep as wasted time?
A. Certainly. And every decade we subtract more and more minutes, to produce and consume more. There are even classes that teach how to sleep less, be more productive, and feel great! Personally, I don’t see the point of this modern trend of wanting to sleep less, because sleep is like a huge repair workshop where all the cells of our body are maintained. And the mechanics have to take their time in this workshop. We can’t repair in four hours what we’ve worn down in the other 20.
Q. And yet, we always have the words “fatigue” and “exhaustion” in our mouths.
A. The thing is, in some circles, saying you barely slept is even considered a positive trait. On the other hand, those who sleep the necessary hours are immediately labeled as lazy. Professionally, always being active is valued. It’s almost a question of status. We need to change this perception. Now, thankfully, there seem to be movements that are beginning to alert us that something is wrong. For example, in the great quit taking place in the United States, lack of rest is most likely the root of the problem.
Q. Scientific evidence has already confirmed that sleep is a pillar of health.
A. People complain of poor sleep, but they don’t associate it with illness. It is their mistake. Sleep is as important as diet or exercise – maybe even more so, because you can go days without eating, but not without sleep. But it’s hard for sleep to be seen as a pillar of health in this competitive society that is all about production and consumption.
Q. Is capitalism depriving us of sleep?
A. Capitalism has exhausted us. Everyone needs to know how much sleep they need to be well. And stick to it. Sleep can’t be the last thing we spend our time on until we’ve managed to complete all the other tasks. On the contrary, it should be a priority in our lives. We have to set a few hours and be disciplined, be brave in that sense. From a health perspective, sleeping is the most revolutionary act we can do.