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Power of the Wind:
Preventing Heat Stroke during Summer Heat Waves

Mayumi Matsuda
Assistant Professor, Faculty of Human Sciences, Waseda University

The necessity of preventing heat stroke during heat waves

According to the Fire and Disaster Management Agency, Ministry of Internal Affairs and Communications, a total of 26,860 people with heat stroke were taken by ambulance to hospitals during the period from May 27 to July 28, 2013 in Japan.1) Preventive measures against heat stroke are regarded as an important issue that is also related to global warming and the heat island phenomena. As a measure against global warming, there is an increasing need to save electricity. Under these conditions, we have to devise ways of preventing heat stroke efficiently and keeping ourselves comfortable. This article summarizes preventive measures against heat stroke and possible ways to beat the heat in reference to The guideline of heat disorders prevention in daily life, ver. 32) issued by the Japanese Society of Biometeorology and our ongoing experiment in hot environments.

Causes and symptoms of heat stroke

The major causes of heat stroke are dehydration and excessive elevation of body temperature. Its initial symptoms include malaise, dizziness, headache, nausea, and convulsions, and when the disease worsens, disturbed consciousness or death may occur.2) Heat stroke is preventable, however, if we take actions to prevent dehydration and excessive elevation of body temperature.

Prevention of dehydration

According to The guideline of heat disorders prevention in daily life, ver. 3 issued by the Japanese Society of Biometeorology, it is recommended to drink about half a glass (a glass = 200 mL) of water about once every hour during daytime and a glass of water before bedtime, on waking up, and before/after a bath, as a target for the necessary amount of water intake in daily life. It is especially important for elderly people to try to drink water before they feel thirsty, because they may not be aware of their thirst. Furthermore, it is important to take salt together with water to prevent dehydration when you sweat heavily during exercise or work.2)

Effect of the wind

In order to prevent heat stroke, it is important to remove body heat efficiently, as well as to prevent dehydration. We are currently conducting an experiment to cool the head or neck in human subjects, and we have realized the effectiveness of cooling by wind. Especially when a person has an elevated body temperature and is sweating, wind from an electric fan significantly decreases the temperature of the skin. In this experiment, subjects wear water circulation clothes (a tube is placed inside the clothes to allow circulation of hot water at the preset temperature) in which hot water at 45℃ is circulated to heat the whole body in order to maintain a high body temperature. They also wear rain gear on the whole body to restrict air permeability. By applying wind from an electric fan to the face of people who has an elevated body temperature and are sweating, the temperature of the esophagus measured behind the heart is also decreased. In other words, wind can cool not only the surface of the skin but also deep inside the body. The cooling effect of wind is remarkable. This effect is attributable to the sweat evaporation enhanced by wind.

When sweat evaporates, heat is removed from the body surface by the heat of vaporization. However, sweat that drips down without evaporation can hardly remove heat. By applying wind to the body, the evaporation of sweat is enhanced, resulting in the efficient diffusion of the heat stored in the body. Another benefit of cooling by wind is that wind can cool large areas at once. The Japan Sports Association recommends a method of pouring water over the whole body with strong wind from an electric fan for people with suspected heat stroke, as a cooling method for the body in regular situations. It is also good to cool large blood vessels in the neck, underarm, or base of the legs with an ice bag or ice pack.3) Cooling by wind is also recommended as an emergency measure against heat stroke. Again, wind can remove body heat efficiently. We should make the maximum use of the effect of wind to prevent heat stroke during sports, or to keep us comfortable at home or office.

Effect of the wind at office or during sport

The Ministry of the Environment is proposing a lifestyle called Cool Biz, with which we can feel comfortable even when the temperature of air conditioner is set to 28℃, as part of the measures against global warming. However, many people who are working at a temperature setting of 28℃ may feel hot. At a room temperature of 28℃, you will not feel hot if you wear a half-sleeve shirt and shorts and take a rest, but you will feel hot if you move and your metabolism is boosted. You need to use some tools to feel comfortable in an office room set to a temperature of 28℃. With wind from an electric fan or other appliance in addition to air conditioner, evaporation of sweat is enhanced and you will feel cool and be freed from sticky feeling of the skin. It is also good to have folding fans or round paper fans.

Diffusion of heat by wind is also effective to prevent heat stroke or improve performance during sports. How much body temperature can be lowered during games is important to relieve fatigue and prevent heat stroke. Many people might imagine that ice packs or ice bags are cooling tools, but if electric fans or large round paper fans are available, the whole body of more than one player can be efficiently cooled at once.

Considerations for people who are susceptible to heat stroke

According to the data released by the Ministry of Health, Labour and Welfare, the number of deaths from heat stroke in 2010 was the largest since 1964 when statistics on heat stroke began to be collected. A total of 1731 people died from heat stroke in 2010, and people aged 65 years or older accounted for about 80% of these deaths. About 46% of deaths from heat stroke occurred at home.4) Heat stroke in elderly people tends to worsen. In addition, people with underlying disease, those who are taking medication, obese people, and infants are also susceptible to heat stroke.2) Of course, such people with a high risk of heat stroke must watch themselves, but people around them also need to give consideration to these people. It is important to talk to each other, especially on hot days, to ensure that they are getting plenty of fluids and that the room is not too hot.

Information about preventive measures against heat stroke

In this article, I have explained the effect of cooling by wind on the basis of our ongoing experiment. As preventive measures against heat stroke, it is important to check weather information, use air conditioning as necessary (especially rooms of elderly people must be controlled at 28℃ or less), refrain from going out or doing exercise on hot days, drink water often, and maintain good physical condition.2) As tolerance against heat is different for different people, measures that include consideration for individual differences are also required. A lot of information about preventive measures against heat stroke is available on the Internet. For example, The guideline of heat disorders prevention in daily life, ver. 3, to which I referred in writing this article, is available on the website of the Japanese Society of Biometeorology. Preventive measures against heat stroke during exercise are also available on the website of the Japan Sports Association. Furthermore, the Ministry of the Environment provides information for prevention of heat stroke.5) Please utilize the information mentioned above to take preventive measures against heat stroke.

Heat stroke is preventable by taking the appropriate actions. In order to prevent heat stroke, it is important to drink water often and diffuse body heat efficiently. I would like to recommend using wind in addition to air conditioning as an efficient cooling method of the body. In hot days, please remember to talk with the people around you in order to stay healthy through the summer.

References

1) Fire and Disaster Management Agency, Ministry of Internal Affairs and Communications: Statistics on the number of people with heat stroke taken to hospitals by ambulance
http://www.fdma.go.jp/neuter/topics/heatstroke/pdf/sokuhouti.pdf (as of July 31, 2013)
2) Japanese Society of Biometeorology: The guideline of heat disorders prevention in daily life, ver. 3
http://www.med.shimane-u.ac.jp/assoc-jpnbiomet/pdf/shishinVer3.pdf (as of July 31, 2013)
3) Website of the Japan Sports Association: How to prevent heat stroke (as of July 31, 2013)
4) Ministry of Health, Labour and Welfare: Statistics on the number of deaths from heat stroke in 2010
http://www.mhlw.go.jp/toukei/saikin/hw/jinkou/suii10/dl/s08.pdf (as of July 31, 2013)
5) Ministry of the Environment: Information for prevention of heat stroke
http://www.wbgt.env.go.jp/ (as of August 4, 2013)

Mayumi Matsuda
Assistant Professor, Faculty of Human Sciences, Waseda University

[Profile]
She graduated from Department of Nursing, Ibaraki Prefectural University of Health Sciences and earned her M.S. from the Graduate School of Human Sciences, Waseda University and Ph.D. from the Graduate School of Sport Sciences, Waseda University. She worked as a nurse at Yokohama City University Hospital, part-time nurse at Medical Corporation Jiokai Seto Hospital, Visiting Researcher at Advanced Research Center for Human Sciences, Waseda University, and Visiting Fellow at the University of Wollongong before assuming her current position.

[Publications (co-authored)]
1. L. I. Crawshaw, M. Nakamura, T. Yoda, K. Tokizawa, Y. Uchida, K. Nagashima, 2011, Thermoregulation, P. Auerbach ed. Wilderness Medicine, Mosby/Elsevier, Philadelphia, 104-105
2. M. Nakamura and K. Kanosue, 2010, Temperature sensation and thermal comfort [ondo kankaku to onnetsuteki kaitekikan], K. Kanosue ed. Encyclopedia of body and temperature [karada to ondo no jiten], Asakura Publishing, Tokyo, 37-39