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Hot Summer Days Can Make Sick People Sicker

Extreme heat can affect anyone, but you don't have to become a victim.
By
WebMD Feature
Reviewed by Louise Chang, MD

Most people know that extreme heat can make us sick. But we may think of heat-related illness as something that only affects people who are overdoing it -- like overheated marathon runners, professional athletes, or new recruits doing drills on military bases.

But most people who die from heat stroke in the U.S. -- about 400 every year, and possibly more -- don't get it from overexerting themselves on a muggy day. In certain people during high temperatures, it's all too easy to develop heat stroke while sitting perfectly still on the couch.

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Heat stroke occurs when the body is unable to regulate its temperature. The body's temperature rises rapidly, the sweating mechanism fails, and the body is unable to cool down.

"People just don't understand the risks of extreme heat," says Michael McGeehin, PhD, MSPH, director of the division of Environmental Hazards and Health Effects, at the CDC's National Center for Environmental Health. "They aren't aware how quickly they can get into trouble."

And while heat-related illness can be a problem for anybody, the risks aren't equal. People who have certain medical conditions or who take some medications to treat those conditions are at a greater risk of having problems in hot weather.

"Any chronic disease lowers your threshold to heat injury," says James Knochel, MD, from the Presbyterian Hospital of Dallas. "There's no question that people with medical conditions are at higher risk, although they may not know it."

"If you go to the ER of a hospital and look at the people who are there for heat stroke," Knochel tells WebMD, "most of them are going to be older and have cardiovascular disease, or diabetes, or another chronic condition."

But these illnesses and deaths can be prevented. If you are at risk, then you can learn how to protect yourself.

Heat and Disease

In order to work well, the body has to stay at a normal temperature. If it heats up even by a few degrees, your body starts to cool itself. The most obvious and familiar reaction is that you start to sweat. As the hot perspiration evaporates off your skin, you're cooled down.

The body reacts to heat in many other, less obvious ways. For instance, hot temperatures make your heart beat faster. That's not only if you're exercising. Even if you're sitting perfectly still, your heart will be beating harder when you're hot. That's because the heart is working harder to push blood to the skin and muscles. Getting blood closer to the surface of the body gets it to cool down and helps with sweating.

While this system works pretty well in a healthy person, it may not work so well in people with chronic illnesses.

"Anything that interferes with our natural cooling system could lead us to heat exhaustion and heat stroke faster," McGeehin tells WebMD. "A lot of medical conditions can do that."

When the body can't get rid of excess heat fast enough, the cooling system eventually breaks down, and the organs begin to overheat. If they get hot enough, they'll stop working. Confusion, seizures, permanent disability, and even death can occur if treatment isn't provided. That's heat stroke and it's a medical emergency.

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