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Why High Temperatures Make Us Sleepy – Healing Practice



Why we need a nap on hot summer days

A special circuit in the brain seems to be responsible for the fact that we sleepy when it’s hot and may have to take a nap in the afternoon. This is how the siesta, common in hot countries, could come to you biological mechanism decrease and corresponding adjustments to the daily routine would also be desirable in this country – at least in summer.

In a study of fruit flies, researchers from the Northwestern University in Evanston (USA) a “Brain Circuits of the Thermometer” evidence that may explain why we get tired from the heat. The results of the corresponding study were published in the trade magazine “Current biology“published.

Climate influences behavior

The climate has considerable effects on our health and also influences all human behavior, hence Ingestion about activity level until sleep-wake cycleexplains the research team.

“Temperature fluctuations have a profound effect on the behavior of humans and animals, and tell animals that it’s time to adapt to the changing seasons”explains the author of the study Professor Marco Gallio from the Department of Neurobiology at Northwestern University.

the “The effects of temperature on sleep can be quite extreme, with some animals choosing to sleep late for an entire season – think of a bear’s hibernation.”like that Professor Gallio further away.

Temperature affects sleep centers in the brain

the biological mechanisms, that control this cycle remain largely unclear. The specific brain circuits involved in the interaction between temperature and sleep centers are relatively unexplored, experts point out.

In 2020, a type of thermometer was first identified in the brain that is only active in cold weather, researchers report. The current study has now looked at a similar “thermometer circuit” for high temperatures.

Heat receptors identified in fruit flies

The research team could “absolute heat receptors” in the heads of fruit flies (Drosophila) which react to temperatures above 25 degrees Celsius – the fly’s preferred temperature. Neurons in the brain that receive heat information were part of the larger system that regulates sleep.

“When the warming circuit (…) is active, the target cells that promote naps stay longer. This leads to an increase in naps which keep flies away from the hottest part of the day”explains the research team.

Different circuits for hot and cold

According to the researchers, the different circuits for hot and cold temperatures make perfect sense because hot and cold temperatures have very different effects on the body. physiology and behaviour may have.

This separation may also reflect evolutionary processes based on Earth’s heat and cold cycles. Next, the researchers want to set common goals for cooling and heating cycle to find out how the two affect sleep.

“We have identified a neuron that may serve as an integration site for the effects of hot and cold temperatures on sleep and activity in Drosophila”according to the author of the study Michael Albert, a graduate student in the laboratory of Professor Gallio. This is an interesting starting point for follow-up studies.

Long-term behavioral effects?

In the context of global warming, researchers are also interested in the long-term effects of temperature on behaviour and the physiology interested parties, as this could also allow conclusions to be drawn about the adaptability of the species to change.

In humans, taking an afternoon nap on a hot day seems like a conscious choice, and in some parts of the world it’s a cultural norm. But do we really decide or are we programmed to take a nap in the heat?

“In flies, of course, it’s not culture, so there could be a very powerful biological mechanism that’s overlooked in humans.”stress Professor Gallio. (fp)

Author and source information

This text corresponds to the specifications of the specialized medical literature, medical guidelines and current studies and has been verified by health professionals.


  • Northwestern University: Why the Heat Makes Us Sleepy (published 08/17/2022),
  • Michael H. Alpert, Hamin Gil, Alessia Para, Marco Gallio: A Hot-Temperature Thermometer Circuit Adjusts Drosophila Behavior to Persistent Heat; in: Current Biology (published 08/17/2022),

Important Note:
This article contains general advice only and should not be used for self-diagnosis or treatment. It cannot substitute a visit to the doctor.

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