Sleep off the weekend?
Scientists have explained why it is dangerous
Alfiya Yenikeeva, RIA Novosti
Monday is a hard day. And scientists have explained why. The difference in the time of waking up on working days and weekends leads to heart problems and excess weight, causes headaches, chronic fatigue, some experts say. Others note that the source of diseases is in the quality and quantity of sleep. The correspondent of RIA Novosti visited a professional conference of somnologists and tried to figure out how to sleep properly and why it is impossible to get enough sleep on weekends.
Around the World with Diabetes
At the end of 2011, in one of the laboratories of Harvard University (USA), a group of 24 volunteers learned to sleep strictly according to a schedule. The volunteers had to spend no more than 5.6 hours a day on sleep, while the day for them consisted of 28 hours. In reality, a person can get into such conditions if he flies four time zones to the west every day. In the laboratory, this situation was simulated by closing all the windows and clearing the room of the clock so that nothing would indicate what was happening outside. The scientists who started the experiment wanted to see how jetlag – a time zone change syndrome that occurs when flying to distant countries – affects health. The results were depressing. Three weeks later, three test participants were in a prediabetic state, the rest also had excess sugar in their blood. The metabolic rate of all volunteers dropped by an average of eight percent.
"If the participants do not change their physical activity regime and diet, then in the next year with such a metabolic rate they will gain about 12.5 pounds (about five and a half kilograms. – Ed.)," the authors of the study concluded.
Jetlag in working mode
German physiologists believe that in order to experience all the charms of jetlag, it is not necessary to travel to distant countries. The imbalance between the daily routine accepted in society and the biological clock of a person occurs weekly with everyone. On Friday and Saturday, people tend to wake up and go to bed late, and on weekdays they have to get up a few hours earlier. It's like flying to a different time zone. Experiencing this regularly is a serious stress for the body. According to several scientific studies at once, such a constant "social jetlag" causes a whole bunch of diseases – obesity, headache, chronic fatigue – and increases the risk of developing cardiovascular diseases.
According to the work of researchers from the University of Arizona (USA), every hour of the difference between waking up on weekdays and weekends increases the likelihood of strokes and heart attacks by 11 percent.
Sleep in debt
"Social jetlag is not a myth. And it is connected with the time when it gets light and dark outside. Lighting is one of the main factors affecting a person," said Mikhail Bochkarev, senior researcher at the Somnology Group of the Almazov National Research Center (St. Petersburg), speaking at the conference "Actual Problems of Somnology", held recently at the I. M. Sechenov First Moscow State Medical University. "I don't agree with that. All we see is a person depriving himself of some amount of sleep. Naturally, this is very bad. This can be called a social jetlag, desynchronosis, whatever you like, but it has absolutely nothing to do with lighting in Moscow," Arkady Putilov, head of a separate research group for mathematical modeling of biomedical systems at the Federal Research Center for Fundamental and Translational Medicine (Novosibirsk), entered into a discussion with a colleague.
Not so long ago, the scientist's team analyzed data on sleep time on weekdays and weekends published for 200 samples with an average age of study participants from six months to 60 years. According to Putilov, no substantiated evidence has been found that sleeping off on weekends is harmful or that the need to get up an hour earlier on weekdays is harmful to health.
"Chronobiology is a serious science based on mathematical theory. If you want to explain something in terms of chronobiology, you have to show on the model how it works. We have created a model for regulating the sleep–wakefulness cycle. The differences between the model's predictions and what was in these samples turned out to be minimal. So, our model does not confirm either that with early awakenings on weekdays, sleep debt accumulates, or that it partially returns due to longer sleep on weekends. We have not seen evidence that owls suffer more from social desynchronosis, as some studies claim. Sometimes owls sleep longer on weekends, sometimes larks. There is no general trend observed here. And most importantly: if the shift of the sleep phase relative to the circadian rhythm phase is no more than an hour, social desynchronosis will not occur," the scientist explained.
Who sleeps little, eats a lot
Since 2006, when a researcher from Mark Wittmann of the University of Munich (Germany) introduced the concept of "social jetlag", several hundred scientific publications have accumulated on how harmful it is to limit sleep on weekdays and get enough sleep on weekends. One of the studies conducted in 2015 on five hundred middle-aged people showed that social jetlag correlates with insulin resistance (and this is one of the main signs of a prediabetic condition), a reduced level of "healthy" cholesterol and a higher body mass index. "Many metabolic processes have a daily rhythm, normal sleep is necessary for their normal regulation. If a person has a bad or short sleep, we see the development of insulin resistance. The metabolic profile becomes prodiabetic. In addition, there are problems with overeating. Sleep disorders lead to an increase in the level of ghrelin (hunger hormone) in the body and a decrease in the level of leptin (a marker of energy abundance). That is, a person's appetite unconsciously increases. This has been tested in laboratory studies on both animals and humans – the same thing happens all the time. As soon as acute chronic sleep deprivation is fixed, we observe dysregulation of appetite, an increase in total calorie intake per day and excess weight," said Alexandra Puchkova, a junior researcher at the Laboratory of Sleep and Wakefulness Neurobiology at the Institute of Higher Nervous Activity and Neurophysiology of the Russian Academy of Sciences.
According to her, children and teenagers are in a special risk group. Schoolchildren, especially high school students, chronically lack sleep on weekdays, which is why eating habits are broken just at the moment when they are just being formed. This leads to metabolic problems and obesity.
Indirectly, such conclusions are confirmed by a recent American study. Analyzing the activity of more than 246 thousand Twitter users from 2012 to 2013, scientists found that the level of social jetlag correlates with overweight. In those areas of the United States where the difference between waking up and going to bed on weekdays and weekends was particularly noticeable, there were higher rates of obesity.
On the contrary, Arkady Putilov believes that social jetlag is most likely not related to health problems.
"We need to do something about the idea of social desynchronosis, because it describes something else. I don't want to say that it doesn't exist. Yesterday, early in the morning, I was riding the subway and, for the sake of interest, counted how many people in the nearest seats are sitting with their eyes closed. It turned out that six people – with open, six – with closed. That is, the phenomenon exists, but whether there is some kind of physiological mechanism behind it, we still need to prove," the scientist noted.
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