Why are heatwaves dangerous, and what effects does extreme heat have on the body?

 Extreme heat poses serious health risks, particularly for the elderly and those with pre-existing conditions. Here's what you should know.


Heatwaves are becoming more frequent, more intense, and last longer than ever before as a result of climate change, with deadly consequences. According to one model, extreme heat could be responsible for 356,000 deaths in 2019. We explain how heat affects the body and how to stay safe in this section.

What exactly is a heatwave?

A heatwave is a period of unusually hot weather that lasts more than two days. A heatwave in London is defined as three or more consecutive days of temperatures above 28°C; in other places, the threshold varies depending on the region's average.

What does extreme heat do to our bodies?

The human body reacts to high temperatures in two ways: it dilates blood vessels in the skin and it sweats.

By increasing blood flow to the skin, more heat is lost to the environment. Sweat cools the body as it evaporates from the skin.

These responses aid in maintaining core body temperature between 36 and 37°C, which is required for metabolic functions to function normally.

They may, however, have unintended consequences. Blood vessel dilation lowers blood pressure, forcing the heart to work harder to circulate blood throughout the body. In people who already have a heart condition, this can lead to a heart attack.

Excessive sweating can also lead to a loss of salt in the body. A low sodium level in the blood can cause nausea and headaches in severe cases.

What causes heat-related deaths?

Deaths from cardiovascular and respiratory diseases are more common during heatwaves. However, it is not always clear when a person's death was caused by heat, according to Ana Nunes of the University of Warwick in the United Kingdom. "The link between deaths during or immediately after a heatwave due to heat exposure is difficult to establish," she says, adding that "mortality attributed to extreme heat is almost certainly underestimated."

Who is most vulnerable to extended high temperatures?

According to studies, the people most at risk from high temperatures are the elderly, the isolated, those with pre-existing heart conditions, and those without access to air conditioning. According to one study, people with pre-existing mental health conditions are also at a higher risk of dying from extreme heat. Researchers speculate that this could be due to the effects of medication or a failure to take the necessary precautions to stay cool during a heatwave.

Infants are also vulnerable to hot weather because they have a much larger body surface area to mass ratio than adults, allowing them to absorb more heat in hot conditions. In the United States in 2019, 53 children died from heat-related illnesses after being left in a car.

What are the risks of extreme heat during pregnancy?

According to one study, about 25,000 children are born prematurely in the United States each year as a result of exposure to extreme heat. Another study discovered that pregnant women in low to middle income countries who experienced extreme heat in the last week before giving birth had a higher risk of preterm birth and stillbirth.

Do you get more used to heat if you grow up in a hot country?

Acclimatisation is the physiological adaptation to hot weather that anyone can undergo over a period of several days. A person who has become accustomed to the heat will sweat more and secrete sweat with a lower salt concentration. This aids in the maintenance of the body's salt balance. To maximize heat transfer to the environment, the rate of skin blood flow will also increase.

How do I stay safe and cool?

Drink plenty of fluids and stay as cool as possible during the heatwave. Close the curtains in rooms that face the sun during the day. Wear sunscreen to protect your skin from UV rays, and dress loosely to keep cool. Exercise should also be avoided outside during the hottest times of the day.

What is the difference between heat stroke and heat exhaustion?

Heat exhaustion happens when your body loses too much water and salt. This can result in headaches, dizziness, and rapid breathing. If you can cool down within half an hour, it is usually not serious.

However, heat exhaustion can progress to heat stroke, a serious medical condition that occurs when your body overheats severely and causes loss of consciousness. If someone is still feeling ill from the heat after 30 minutes of resting in a cool place, call 911 immediately.

How are heat stroke and heat exhaustion treated?

Finding a cool place to rest and drinking plenty of water can help treat heat exhaustion. If you suspect someone is suffering from heat stroke, call 911 right away.


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