July 5, 2024

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Conducted an “awareness survey on measures against heatstroke and the use of air conditioners during a night's sleep in the tropics”
There are almost the same number of air conditioners when sleeping at night in the tropics: the “leave it on” and the “off timer operation group” are the mainstream

People who are active in heatstroke countermeasures tend to “leave the air conditioner on” until morning

Dr. Yasufumi Miyake, an emergency physician, points out the importance of “awareness of physical disorders,” “sleep quality to restore the body,” and “humidity control.”

Research Summaries

• About 70% (69.2%) of people “feel unwell” when sleeping or waking up on a tropical night
  There is also a possibility that this kind of disorder is an early symptom of heatstroke
• It was found that about 1 in 3 people (33.7%) are actively “not taking measures against heatstroke” on tropical nights
  The most common reason for not being aware of countermeasures is “because I have never felt in danger”
• The heat of tropical nights may interfere with sleep for many people (76.2%)
  The number one concern is “I wake up hot” (45.5%), and the second place is “I can't fall asleep easily” (33.0%)
• About 80% (81.6%) of people use air conditioning during a tropical night's sleep
  The “driving group with the left on” (46.1%) and the “driving group with the timer off” (43.5%) are mainstream and have almost the same number
• Be careful of the rise in the “heat index (WBGT)” when sleeping at night in the tropics
  People who often work on heatstroke countermeasures tend to “leave the air conditioner on”

About 70% of people “feel unwell” when sleeping or waking up on a tropical night
There is also a possibility that this kind of disorder is an early symptom of heatstroke

There are various early symptoms of heatstroke. Dr. Miyake (Director, Teikyo University Medical School Hospital Advanced Critical Care Center) says, “On a tropical night, if you feel unwell during sleep or when you wake up despite falling asleep without feeling uncomfortable, I want you to doubt the possibility of mild heatstroke.”

This time, 9 symptoms seen in the early stages of heatstroke were listed, and when asked if they had felt these symptoms during a tropical night's sleep or when waking up, nearly half felt “fatigue” (45.7%), and the results showed that about 70% (69.2%) of people felt some kind of disorder, such as “abnormal sweating” (18.3%), “rise in body temperature” (16.8%), “headache” (15.5%), and “standing dizziness” (9.2%).

Professor Miyake says, “Fatigue in particular can be felt due to various factors other than the initial symptoms of heatstroke,” but he also talks about the fact that it is most common as an early symptom of heatstroke during the summer season. From these results, it can be seen that there is a possibility that many people, including mild ones, developed heatstroke due to the effects of tropical nights.

It turns out that about 1 in 3 people are actively “not taking measures against heatstroke” on tropical nights
The most common reason for not taking measures is “because I have never felt in danger”

In response to the possibility that many people have developed heatstroke, including mild ones, due to the effects of tropical nights, when checking whether heatstroke countermeasures are being taken on tropical nights, about 1 in 3 people (33.7%) answered “no countermeasures have been taken” in this survey.

When people not taking measures against heatstroke on tropical nights were asked why, the most common results were “because I never felt dangerous” (43.0%), followed by “because I didn't know specifically how to prevent heatstroke during sleep” (26.8%), and “because I didn't know there is a risk of getting heatstroke at night or during sleep” (16.8%).

Professor Miyake said, “Each person has a different environment where they spend a tropical night, such as how well ventilated the house is, but if you don't take any countermeasures because you aren't really aware of the risk of heatstroke or don't know how to prevent heatstroke,” he also pointed out the importance of being aware of the risk of heatstroke, and working on measures such as devising ways to use an air conditioner and staying hydrated before going to bed in particular.

The heat of tropical nights may be interfering with the sleep of many people
The number one problem is “I wake up because it's hot,” and the second place is “I can't fall asleep easily”

On tropical nights, it seems that there are various problems other than the possibility of heatstroke and physical disorders that are suspected. When asked about “summer tropical night sleeping problems,” it was found that only 23.8% of people had no particular worries, and about 3 out of 4 people (76.2%) had some kind of trouble.
Among these problems, the most common one was “I woke up because it was hot” (45.5%), followed by “not being able to fall asleep easily” (33.0%). For many people, it can be seen that the heat interferes with sleep. Professor Miyake says, “There is a possibility that being aware of good quality sleep may lead to a decrease in the risk of heatstroke the next day.” It seems that it can be said that creating a comfortable sleeping environment is also important as a measure against heatstroke.

About 80% of people use air conditioning when sleeping at night in the tropics
The “driving group with the left on” and the “driving group with the timer off” are mainstream and have almost the same number

Professor Miyake says, “Appropriate use of air conditioners is important for heatstroke countermeasures.” First, when we investigated the percentage of people who use an air conditioner when sleeping on a tropical night out of the total, the result was about 80% (81.6%). While there are few people actively working on heatstroke countermeasures, based on the reality that there are many people who are worried about the heat at tropical nights, it seems that many people use air conditioners regardless of whether they are aware of heatstroke countermeasures or not.

Next, we investigated how people use air conditioners on tropical nights. “Leave it on until morning” (46.1%) and “set a timer so that it runs off while sleeping” (43.5%) both exceeded 40%, and the result was almost the same number. According to this survey, there is no big difference in power saving awareness or trouble during sleep between the “driving group with the left on” and the “driving group with the timer off,” and it seems that it can be said that it is a difference in habits.

Be careful of the rise in the “heat index (WBGT)” when sleeping at night in the tropics
People who often work on heatstroke countermeasures tend to “leave the air conditioner on”

We also investigated how to use air conditioners due to differences in awareness about heatstroke countermeasures. As a result, it was found that people working on heatstroke countermeasures tend to use air conditioners on tropical nights. Also, the result was a high percentage of people actively working on heatstroke countermeasures who answered “doing well” who “left it on” until morning.

When sleeping in summer, when the air conditioner is not turned on, the indoor temperature and humidity gradually rise, and it may become an environment where it is necessary to be alert for heatstroke. An index called the “heat index (WBGT)” *1 is used to evaluate the risk of heatstroke. If you leave the air conditioner “on” until morning, it is also possible to reduce WBGT to the extent that it is generally said that the risk of heatstroke is low. On days when the temperature and humidity are high, it is thought that “leaving the air conditioner on” until morning rather than turning it off with a timer will lead to a comfortable sleep.

1. Not only temperature but humidity is important for creating a comfortable space

In order to create a comfortable space, it is important to adjust not only the “temperature” but also the “humidity.” It is said that if the humidity changes by 20%, the sensed temperature changes by about 4 degrees Celsius. In the thermography visualization test*2 performed by Daikin in the test room, it was confirmed that an increase in skin temperature was confirmed in an environment with a temperature of 28 degrees Celsius and humidity of 85%, and then when the humidity was set to 60% without changing the temperature, the skin temperature on the hands and face of 10 out of 12 subjects dropped markedly.
An index called the “heat index (WBGT)” is used to evaluate heatstroke risk. When the indoor temperature or humidity rises, it may reach WBGT, which requires vigilance against heatstroke. If the room temperature is high and humidity is a concern, it is important to use an air conditioner to control the temperature and humidity.

*2 Results of visualization verification tests using thermography:

2. When using the air conditioner when sleeping in the summer, it is recommended to “leave it on” until morning

There may be many people who use an off timer because they are reluctant to leave the air conditioner on during sleep. Therefore, in a general house in Yokohama City, Kanagawa Prefecture, Daikin measured changes in indoor WBGT by “leaving the air conditioner on until morning,” and “off timer operation,” which uses an off timer to turn off the air conditioner 3 hours after going to bed, respectively. Whereas there was no significant increase in WBGT in “left on operation,” in the case of “off timer operation,” the result was that WBGT gradually increased after the air conditioner was stopped.

If the air conditioner is turned off while sleeping, there is a possibility that WBGT will reach a value that requires vigilance against heatstroke at dawn. On days when the temperature and humidity are high, the temperature is set to an appropriate temperature, and it seems that “leaving it on” until morning will lead to a comfortable sleep.