The hotter it is, the more that needs to be done for the body to regulate its core internal temperature.
According to the Centers for Disease Control and Prevention (CDC), there was a total of 7,415 deaths in the US between 1999-2010 as a result of extreme heat. Despite being highly preventable, heat-related illness can be lethal.
In Europe in 2003, unprecedented heatwaves were responsible for an increase in deaths. In England, temperatures reached record highs (101 degrees) over a period of 9 days.
"There is considerable evidence that heatwaves are dangerous and can kill," states Graham Bickler of Public Health England. "In the 2003 heatwave, there were 2,000 to 3,000 excess deaths in England. Across Europe, there were around 30,000 excess deaths."
Extreme heat is defined by the CDC as "summertime temperatures that are substantially hotter and/or more humid than average for location at that time of year." Although certain groups of people are more susceptible to these temperatures than others, anyone can be affected in the wrong situation.
In this Spotlight, we take a look at the effects extreme heat have on the body and the measures that can be taken to prevent dangerous conditions such as heat stroke from occurring.
Regulating core internal temperature
Problems begin to occur in extreme heat when the body struggles to cool itself down properly. The human body has a very precise core internal temperature that needs to be maintained - a state that is known as homeostasis. A healthy core temperature should sit between 98 degrees and 100 degrees.
A part of the brain known as the hypothalamus is responsible for controlling the way in which the body regulates its temperature. If the body's core internal temperature starts to get too low or too high, then it can send signals to glands, muscles, nerves and organs activating mechanisms to adjust the body temperature.
The mechanism the body normally uses to cool itself is sweating. Liquid containing salt is released from the sweat glands, and when this sweat evaporates from the body, the body cools down. However, on some occasions, sweating is not enough.
For example, if humidity is high - when large amounts of damp air are trapped near the ground - sweat will not evaporate as quickly as it normally would, meaning that the body's ability to cool itself down is compromised.
A number of other factors limit how well the body can regulate temperature and, therefore, increase the risk of heat-related illness. These include the following:
- Old age
- Youth (age 0-4)
- Overweight and obesity
- Heart disease
- Mental illness affecting judgment
- Medical conditions that limit activity or restrain blood flow
- Use of certain medications
- Use of alcohol.
In terms of medication, there are a number of different reasons why these can increase the risk of heat-related illnesses. Some, such as those taken for Parkinson's disease, can inhibit sweating while others, such as diuretic medications or "water pills," alter the balance of fluids in the body.
When the body is struggling or unable to regulate temperature properly, a number of different illnesses can occur. These vary in severity from heat rash - a common problem in hot work environments - to heat stroke, a medical emergency that can kill.
What types of heat-related illnesses are there?
Heat-related illnesses come in all shapes, sizes and levels of severity. Some present solely external symptoms, some only internal symptoms and some a combination of the two. Some can be debilitating, some can be lethal and some require nothing more than keeping an affected area of skin dry.
Probably the least problematic of the heat-related illnesses, heat rash is caused when the skin becomes irritated due to excessive sweating and sweat that does not evaporate. The rash is formed by clusters of red bumps or small blisters on the skin, commonly in areas such as the groin, the upper chest and in folds of the skin.
Moving to a cooler location such as the shade of a tree can help cool the body down and reduce the risk of heat-related illness.
Young children are most likely to be affected by the condition. Heat rash is best treated by keeping the affected area as dry as possible and moving to a cooler, less humid environment.
Heat cramps are muscle spasms and pains that typically occur in the abdomen, arms and legs. Sweating decreases the level of salt and moisture in the body, and it is low salt levels that cause heat cramps.
These cramps normally occur in association with strenuous activity and exercise, affecting those who sweat a lot during these pursuits. Drinking water and other cool beverages helps, as does stopping strenuous activity for a few hours. If heat cramps persist for an hour, medical attention should be sought.
Heat cramps can also be a sign of more advanced heat-related illnesses - heat exhaustion and heat stroke.
Heat exhaustion takes a little longer to develop than the forms of illness above, occurring after several days of exposure to extreme heat and imbalanced body fluid levels. The condition is due to the loss and inadequate replacement of water and salt from heavy sweating.
People with heat exhaustion can appear pale and sweat heavily, leaving their skin cool and moist. Their heartbeat will be fast but weak, and their breathing is likely to be quick and shallow. In addition to muscle cramps, people with heat exhaustion can experience headaches, nausea or vomiting, fainting and fatigue.
Heat exhaustion is most likely to affect older people, people with hypertension and people carrying out activities in hot environments. People with heat exhaustion should cool their bodies by drinking plenty of water or other cool beverages, taking a cool shower or bath and resting in a cooler environment.
Heat stroke is the most dangerous of all the heat-related illnesses and occurs when the body is unable to regulate its core internal temperature. Within 10-15 minutes, the core internal temperature can rise to over 106 degrees, a dangerous increase that can lead to permanent disability or death if untreated.
The symptoms of heat stroke are far more extreme than those of heat exhaustion. The individual will no longer be able to sweat and, therefore, have red, hot and often dry skin. Their heartbeat will be rapid and strong. Other symptoms include dizziness, throbbing headaches, seizures and unconsciousness.
As heat stroke is a medical emergency, action should be taken as quickly as possible. While immediate medical assistance is summoned, the person's body must be cooled down rapidly by whatever means are available.
Removing clothing, applying ice packs, immersing the individual in cool water, spraying them with a hose, wrapping them in damp sheets, fanning them: all are methods that can help lower body temperature to safer levels.
In all instances of heat-related illness, including heat stroke, moving to a cooler location is one measure that should be taken to improving the situation. This is just one common step that everyone can take to reduce the risk of developing these illnesses.
How to keep your cool
When the body is struggling to cool itself down, cooling down the location that the body is in is a great way to prevent heat-related illness. In fact, the CDC state that "air conditioning is the number one protective factor against heat-related illness and death."
If a person's home is not air conditioned, they can derive benefit from visiting public spaces that are, such as shopping malls or libraries. Exposure to air conditioning for just a few hours a day is enough to reduce the risk of heat-related illness.
The body requires more liquid in extreme heat. Do not wait until feeling thirsty before drinking.
To improve the body's chances of cooling itself down, it is important that people drink enough fluids. In extreme heat, people should drink more water than they normally would and should not wait until feeling thirsty before drinking.
If exercising, the CDC recommend drinking two to four glasses (16-32 ounces) of cool nonalcoholic fluid every hour. Drinking sports beverages can also help by replacing the salt and minerals that are also lost through sweating.
Outdoor exercise is best carried out in the morning and evening rather than the afternoon, as these are the times of day when outdoor temperatures are coolest. Resting in shaded areas will give the body more of a chance to regulate its temperature. It is also important that people take care to pace themselves when exercising or carrying out strenuous activities in hot environments.
Wearing appropriate clothing helps. Loose, lightweight and light-colored clothing is best, as is wearing as little as you can get away with. Accessories that shade the body such as hats and umbrellas are useful. Of course, any skin that is exposed to the sun will need to be adequately protected from its rays.
As sunburn disrupts the skin's ability to cool itself and results in the loss of body fluid, apply sunscreen of SPF 15 or higher around 30 minutes before venturing outside. Be sure to follow the directions on the sunscreen's packaging concerning how frequently it should be reapplied.
In terms of keeping cool, a lot of what can be done is common sense. Large, hot meals should be avoided as they heat the body, as does the use of appliances such as ovens. To cool down, take cold showers or baths or have a swim. Keep an eye on weather reports so you can be prepared for a day of extreme heat if one is forecast.
Look out for each other!
Some of the people who are most at risk from heat-related illnesses are vulnerable individuals who depend on others for care. Be sure to look out for young children, people older than 65, people with chronic and mental disorders and pets during times of extreme heat.
Do not leave children or animals alone in cars, where interior temperatures can rise suddenly in a very short space of time, even when the windows are open slightly.
If working or exercising in hot environments, be sure to monitor the condition of your colleagues and teammates and have them do the same for you. Some heat-induced illnesses can lead to confusion and visible symptoms that others may be better placed to identify.
Most heat-related illnesses are avoidable. By keeping cool, drinking plenty of fluids and being alert, these health conditions should not stop you and others from enjoying a lovely warm summer.