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
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
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.