Heatwave-proof sleep


Sleep under test of the heatwave

Montreal by night

< p class="e-p">With global warming, the number of tropical nights, when the temperature does not drop below 20 degrees Celsius, is expected to increase significantly in Montreal.

They will increase from eight per summer, according to historical data, to 19 over the next thirty years, and then to 28 over the next thirty years, according to the optimistic scenario. If greenhouse gas emissions continue to grow at the current rate, we would even reach 45 tropical nights per summer in 2051-2080.

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For city dwellers, it will be quite a challenge to manage to sleep well in these conditions, underlines Kelton Minor, of the Center for Social Data Science at the University of Copenhagen, Denmark.

Mr. Minor is the lead author of a study, published in May in the journal One Earth, which measured how changes in temperature affect human sleep. Data from 47,000 people in 68 countries was used.

We used measurements taken by sleep tracking bracelets with accelerometers, which measure movement and can detect sleep and activity states, and we combined this data with weather data and local climatological data from weather stations and satellites, he explains.

Study finding: People slept less and the likelihood of having a short night's sleep increased as temperatures became warmer.

Study shows that extreme heat impairs sleepiness at the start of the night.

No surprise for anyone who has ever tried to sleep on a hot summer night with a fan as the only source of cooling.

However, when those poor nights' sleep accumulates, as it will likely do over the next few decades for anyone without air conditioning, the results could be problematic.

According to projections by the Climate Atlas of Canada, the duration of heat waves, that is, the number of consecutive days in which the temperature reaches or exceeds 30°C, will increase from five at the moment to eight in the second half of the 21st century if global greenhouse gas emissions continue to increase at the current rate.

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Already, right now, it is estimated that each person loses around 40 hours of sleep annually due to excessive nighttime temperatures.

By 2099, according to global warming projections, this will be between 50 and 58 hours, depending on the level of adaptation and the climate change mitigation measures that will be implemented.

This is ;a projection that will depend on our ability to adapt to rising temperatures, says Kelton Minor.

If we can engineer new technologies that will help cool nighttime temperatures and protect sleep, the impacts may be less. On the other hand, if the world's population continues to age, people may be more vulnerable to the effect of temperature. If so, we could see those impacts getting even heavier.

The study showed that people over the age of 60 experience the effects of heat more strongly than younger people. This is believed to be because their body temperature tends to drop earlier in the evening, notes Minor. When the outside temperature is higher, it hinders the process of falling asleep and the quality of sleep.

Heat has an undeniable effect on our sleep, says Dr. Roger Godbout, professor in the Department of Psychiatry at the University of Montreal and director of the Sleep Laboratory and Clinic at the Rivière-des-Prairies Mental Health Hospital of the CIUSSS du North-of-the-Island-of-Montreal. It affects how we fall asleep early in the night as much as how we wake up at night.

Anything that upsets our balance will disrupt sleep, Dr. Godbout points out. When we sleep badly, the next day, we will be irritable, impulsive. It causes memory and concentration problems; It's been a bad day.

“Sleep is important for regulating our mood. It is essential for remembering what we have done during the day and for the secretion of certain hormones. »

— Roger Godbout, Director of the Sleep Laboratory and Clinic at the Rivière-des-Prairies Mental Health Hospital of the CIUSSS du Nord-de-l'Île-de-Montréal

Sleeping badly several nights in a row, especially when there is a heat wave, is even more problematic. We create a sleep debt that we will never fully recover.

For those who already suffer from a mental or physical health, bad nights are even more difficult.

Dr. Godbout isn't too concerned, however, about the one-time effect of lack of sleep for most people. Those who suffer from its long-term impact are people who sleep poorly for months and years.

However, one should not hope that one will eventually get used hot nights, he warns.

While animal experiments show that they manage to adapt to a colder temperature within a few weeks, this is not the case for a higher temperature. hot.

This is also what the study seems to show. People who live in hot climates experienced greater sleep erosion as temperature rose, suggesting limited adaptation at this stage, argues Kelton Minor. #x27;intense physical exercise in the evening so as not to increase our body temperature;

  • take a cool shower, but it should only last a few minutes, otherwise we send the message to the body to keep the heat inside the body to fight the cold;
  • avoid taking stimulating drinks, coffee or alcohol, which change body temperature; avoid, for the same reason, heavy and spicy meals late in the evening;
  • drink plenty of water during the day so as not to be dehydrated in the evening, but stop drinking it for two to three hours before going to bed so as not to be awakened during the night by the urge to urinate;
  • do not sleep with animals, as they give off heat.
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