Persistent heat can lead to chronic health problems

Summer temperatures continue to break records around the world, reaching the upper limits of what humans can survive.

While much of the focus on extreme heat is the immediate risk to human health, chronic heat can cause a range of chronic health problems. Days and years of exposure to persistent heat can tax the heart and kidneys, disrupt sleep and challenge our mental health.

And while it’s important to protect yourself from the heat, some people make the mistake of never getting acclimatized to hot weather.

“If people live in air-conditioned environments from — well, some places do it 24/7 — then people’s bodies never really acclimatize to warmer temperatures,” said Kristie Ebi, professor of global health at the University of Washington Center for Health and the Global Environment. “And that is going to be increasingly important as we try to prepare better for a warmer future.”

Chronic heat stresses our heart

To understand why chronic heat can be dangerous for our health, it is important to understand what our body does to try to defend its core temperature. In healthy humans, a body temperature outside of a narrow band between 98 and 99.5 degrees Fahrenheit risks damage to our cells, tissues and organs.

Our ability to thermoregulate in the face of heat relies primarily on our cardiovascular system and kidneys; as a result, chronic heat predominantly strains these two systems, sometimes to the breaking point.

“It’s that physiological vulnerability that ultimately is responsible for the negative health outcomes,” said Ollie Jay, professor of heat and health at the University of Sydney and director of the Heat and Health Research Incubator.

When our central nervous system detects the sweltering heat, it activates our body’s temperature regulatory systems. The blood vessels in our skin dilate and warm blood is directed from our body’s core to the surface for it to cool off. But this can also cause blood pressure to drop, which can be detrimental to those who already have low blood pressure.

To compensate for this drop in blood pressure, our heart increases the rate it circulates the blood by increasing our heart rate, straining our cardiovascular system. For people with an underlying heart condition, the increased strain of heat “increases the likelihood of a catastrophic cardiovascular event,” Jay said.

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