Why is it difficult to fall asleep on a hot day?

On a hot day, sleep is disturbed, and not only the brain does not function properly, but also it is difficult to get a proper rest. [사진=fizkes/게티이미지뱅크]

Sometimes I wake up in the morning. If there seems to be no particular reason to wake up suddenly, ‘heat’ may be the cause.

If you drink a lot of water in the evening, take a long nap, or consume caffeine late at night, you may wake up in the morning. However, if this specific reason is not understood, the room temperature may be the reason for waking up.

The climate crisis is causing global temperature changes. When it’s not too hot yet, the sweltering heat can come suddenly. According to data predicted by scientists over the next 50 years, global warming will continue to increase the temperature, which is estimated to have a profound effect on people’s sleep.

One of the essential conditions for a good night’s sleep is a ‘comfortable temperature’. If you do not meet these requirements, you will fall asleep or wake up frequently.

According to a paper published in the international scientific journal Science and Technology for the Built Environment in 2020, an increase in bedroom temperature and a decrease in sleeping time showed a correlation.

The high temperature was found to interfere with the ‘three-stage sleep’, which leads to deep sleep. During this sleep phase, the brain’s activity slows down to rest, and when the ambient temperature rises, the brain does not get enough rest because the sleep phase is not reached properly or the time spent in this sleep phase is reduced.

A rise in temperature means that it is time to use energy for activity. Our body temperature rises in the morning and afternoon when we are most active. On the other hand, when you sleep, your body temperature goes down and you store energy. In other words, when the ambient temperature rises, our brain can recognize it as an activity time.

When you wake up, your brain isn’t able to do the things it should be doing. Sleep removes unnecessary information accumulated in the brain the previous day and integrates memories. The deep sleep phase also clears out protein debris that is linked to Alzheimer’s dementia and mild cognitive impairment.

As sleep plays such an important role in brain health, it is important to get a good night’s sleep. Neither hot nor cold environments are ideal for sleeping.

In general, experts recommend a bedroom temperature of around 18°C. However, as there are individual differences in sensitivity to temperature, it is better to find the temperature that suits you rather than insisting on 18℃ unconditionally. This may also vary depending on external factors such as humidity and the individual’s health condition.

One of the tricks to getting a good night’s sleep is to sleep with your hands and feet outside the blanket in these days when the air conditioner is not turned on yet. When the temperature difference between the center of the body and the head, hands and feet occurs, it can induce a good night’s sleep.

By Moon Se-young, staff reporter [e-mail]

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