Environment & Science

This is your body on extreme heat

A child drinks from his water bottle amid an ongoing Southern California heatwave in Los Angeles, California on June 26, 2017, where several heat records were set a day earlier.
A child drinks from his water bottle amid an ongoing Southern California heatwave in Los Angeles, California on June 26, 2017, where several heat records were set a day earlier.

Listen to story

Download this story 0MB

No, it's not just you. That convection oven of heat that dries your eyes shut every time you go outside really is making you feel crappy.  

Experts say extreme heat saps energy, shortens breath, fogs thinking and can stop you short with cramping.  

But those ailments can pale in comparison to the deadlier aspects of heat waves.

Heat kills more than 600 Americans a year, according to the Centers for Disease Control and Prevention. That's typically more than all other weather-related deaths combined, according to Dr. David Eisenman with the UCLA Center for Public Health and Disaster.

Public health officials worry about heat-related health conditions because parts of the greater Los Angeles are expected to see up to five times as many days of extreme heat (95 degrees or more) by mid century, according to UCLA data. And heat-related hospitalizations are rising.

To understand more about how heat affects us, KPCC called up Eisenman on one of the hottest days of the summer.

What makes heat so dangerous?

It can affect almost everybody: from the very young, to adolescents, to healthy workers, to the elderly. And a lot of time, the early symptoms of heat illness are brushed off, people don’t recognize them.

Also, most people in newer housing have air conditioning; they don’t see why it’s a problem. Why can’t somebody just find a place to go get in some air conditioning? But it really affects the poor and the elderly disproportionately, and that’s just not obvious. Heat is really, in some ways, kind of a silent killer.

Why does heat bother us at all?

Your body is constantly making heat. Just by running your organs you’re generating heat. So you need to be able to cool off. If you were to just trap that heat in your body, your body would boil up, right? So anything that’s keeping that heat in the body puts you at higher risk.

What are the things that can trap heat in the body?

Wearing the wrong kinds of clothes. Also, if you’re in a lot of heat and sitting in the sun, adding to the heat your body is already making. Or exercising.

We see a lot of this at summertime football practices. Players are under lots of clothes, working really hard, and in the sun. They're absorbing heat. They're creating more heat from their muscle action, and they get dehydrated. 

What’s happens to the body in that situation – the football player running around in the sun?

The overall thing that’s happening is that your core temperature is getting higher and higher, so your body is doing what it can to get rid of the heat. It’s dilating the blood vessels towards the skin. It’ll shunt more blood towards the skin, so heat will evaporate faster. But that means less blood flow is going towards your internal organs.

That sounds bad.  

Your kidney seeing less blood causes kidney damage. Your heart seeing less blood makes the heart work harder, makes breathing harder. It even makes thinking worse. You can start to feel headachy, dizzy, a little confused as time goes on.

Walk me through the early stages of heat exhaustion.

It may be as minimal as ending up with some heat cramps, muscle spasms. That's not terrible. But you're also sweating a lot, you're dehydrating. So since you have less fluid, you start getting dizzy. You’re feeling tired and weak. Something in the effect on the brain causes you to feel nauseous. Cold, clammy skin, a lot of sweating. You may faint.  That's pretty bad.

What happens next?

When it gets really bad, the body can’t keep up any longer with the amount of heat it’s absorbing. It can’t get rid of it fast enough. Then the body reaches really high temperatures, like 103˚F. Now your brain is starting to really be affected. You can lose consciousness. You’re very confused.

That’s where you start to see a feedback loop. So imagine an older adult, 75 years old. Not too healthy, lives alone, and gets too hot. As they start to get dehydrated, and their thinking gets more confused, it’s harder for them to get up and go get a drink of water, or to move to a cool room, or call for help. It becomes a vicious cycle.

How can heat turn deadly?

You can die from heat stroke specifically -- it can cause strokes in the brain. Or you can die from the exacerbation of your underlying medical problems, which is probably more common, actually.

So in our society, a lot of people have diabetes and some amount of kidney dysfunction. They start getting dehydrated, their kidney shuts down, which leads to electrolyte disturbances, which leads to heart attack.

Is that part of why the elderly are more at risk?

Yeah. They’re highly likely to have chronic medical problems already that can get worse with the heat and the dehydration. So if they have diabetes, or kidney dysfunction or heart problems, all of those can get worse.

On top of that, they take medications. They make matters worse. They can slow sweating, they can disable thermo-regulator part of your brain. That makes cooling more difficult.

And it’s an amazing number of medications that do it: antidepressants of an older generation, antihistamines, antipsychotics, some of the heart medications make it harder for the heart to keep up with the strain of the heat. And diuretics, which are used to bring blood pressure down. They’re depleting your body of fluid, so you’re more likely to get a little dehydrated.

What makes small children more at risk?

Little children lose more water compared to an adult. In technical terms, they have a greater surface area to volume ratio. They’re evaporating more and so they’re losing more water, getting dehydrated faster.