A study published in May in the journal One Earth, carried out by a group of researchers from the University of Copenhagen, Denmark, showed that the Earth’s high temperature is linked to the loss, on average, of 44 hours of sleep. per day. . This would represent 58 hours less until 2099.

A study published in May in the journal One Earth, carried out by a group of researchers from the University of Copenhagen, Denmark, showed that the Earth’s high temperature is linked to the loss, on average, of 44 hours of sleep. per day. . This would represent 58 hours less until 2099.

Taissa Stivanin of RFI

The survey was conducted between 2015 and 2017 and involved analyzing data from 47,000 patients from 68 different countries. Participants wore an electronic sleep monitoring bracelet. The scientists then compared the information provided by the device with the local weather conditions.

The conclusion is that from 25º C, at night, the probability of not having restful sleep increases by 3.5 times. The ideal temperature for sleeping is around 19°C. Above this value, the body does not cool enough and this causes people to sleep later and wake up earlier.

How can rising temperatures affect sleep and health? THE RFI asked French psychiatrist Sylvie Royant Parola, a sleep specialist, to evaluate the results published by the Danish researchers.

According to her, the extremely high outside temperature prevents sleep because the brain literally cannot cool itself. “The brain hates heat. If it can’t lower the temperature at night, it will stay alert, like we’re awake,” he says.

For her, the follow-up of thousands of people, in different geographical areas, and at the same time, is one of the most innovative aspects of the study, in epidemiological terms.

“Showing, with graphs, that the higher the temperature, the shorter the sleep, it’s interesting. How will we sleep under certain conditions if global warming increases over the years?” Asks he. The hot and dry climate is the worst for sleeping, the expert points out.

The French psychiatrist, however, warns against the risk of jumping to conclusions that correlate climate change with sleep and criticizes some of the study’s conclusions. “Is this scenario something that will actually materialize, and that will cause, as the study says, our sleep to be drastically altered? To the point of generating a loss of hours of rest? This is a study prospective, yet we are not sure that things will evolve like this”, he repeats. This does not detract from the observation, he underlines, that the high temperatures caused by the effect of greenhouse, in the future, could actually reduce nighttime rest.

Siesta, an ally of the brain

Are there solutions to help the body when the temperature rises too high and it becomes difficult to sleep? In countries like Spain and Greece, for example, which are very hot in summer, people adapt their schedules. As the nights of sleep are shorter, afternoon naps are already part of the routine. This habit can be very beneficial to compensate for sleepless nights, regardless of global warming, recalls the French expert.

She reminds us that other factors already contribute to the lasting effect of modern man’s sleep. Chief among them is industrialization and the emergence of a way of life that prevents people from resting when they feel the need. This has, for example, made the mid-afternoon “doze” fall into disuse, even in hot countries, impacting the quality of sleep, which is less deep.

“For different reasons, chronobiological, we have two ideal times to sleep: at night, around 3 a.m., or otherwise in the afternoon, in the middle of the day,” he explains.

How was this rhythm established? One hypothesis is that our prehistoric ancestors could not sleep through the night because they were at risk from predators or enemy tribes, for example. The arrival of electric light in 1879 definitively broke with our natural functioning, which depends on the sun, the seasons and environmental hazards.

In this context, the nap can be an important ally in restoring what the French psychiatrist describes as the normal physiology of sleep. “When we do not get enough sleep, we are exposed to several complications, mainly cardiovascular. But there are also immunological consequences. Immunity can drop, metabolism can be altered and the risk of developing depression is greater.”

The conclusion is that global warming may induce people to have fewer hours of sleep, which has been happening for decades with industrialization. But it is possible to change habits and prevent health from being affected in the long term.