Recently, I returned from a trip to relations in Ontario, Canada. Shortly after our arrival, a phenomenon known as a ‘heat dome’ enveloped the region, resulting in a week of extreme heat. The temperatures we encountered rose as high as 33 degrees, but the real feel, factoring in humidity, reached an intense 41 degrees.
On one day alone, June 19th, over 100 Canadian heat records were broken, curiously in locations such as Labrador, Newfoundland, New Brunswick, and Nova Scotia, regions which aren’t typically associated with such severe heat.
A nationwide study by Statistics Canada, specifically investigating deaths resultant from extreme heat events, observed the highest surge in fatality rates in cities where such heat events are infrequent and in cities with a high renter population, presumably due to a scarcity of air conditioning. Had it not been for the air-conditioned residence we lived in, we would have struggled to cope with the heat dome’s effects.
A recent publication in Lancet Public Health called The Lancet Countdown: Health and Climate Change in Europe indicates an increase in death rates, health inequality, and climate-sensitive illnesses due to global warming.
Through an analysis of mortality and temperature statistics, climate and health investigator Rachel Lowe and her team concluded that, comparing the period 2003-2012 with 2013-2022, heat-related deaths rose by an average of 17 per 100,000 people across Europe.
But how does the human body respond to such excessive heat to safeguard us? It all starts with the hypothalamus, a small part of the brain that operates like our body’s thermostat. When the external temperature rises, the hypothalamus initiates actions to disperse heat and ensure the body maintains its functions.
One of the initial responses is the expansion, or ‘vasodilation’, of our blood vessels to accommodate more blood flow. This process primarily affects blood vessels nearest to the skin’s surface, facilitating heat dissipation.
The recent heatwave has been connected to several unexpected fatalities in both Canada and the United States and the cause isn’t hard to pinpoint – it’s climate change. The hypothalamus, a region of the brain, controls mechanisms such as sweating which are involved in thermoregulation. Sweat is expelled through particular glands present in the skin, aiding in heat dissipation.
Nonetheless, Prof Adam Taylor, contributing to the Conversation, suggests that the systems that aid in temperature regulation could increase stress on certain parts of our physiology. In high temperatures, the heart’s workload increases significantly, beating an additional ten times per minute for each degree of temperature rise. The blood supply to the skin heightens to between six and eight litres per minute, causing a heart rate spike as the body aims to decrease its temperature, according to Taylor.
Understandably, distinct heart-related illnesses can worsen during heat surges as the cardiovascular system is pushed to its limits. This extra exertion can amplify symptoms related to heart health. To illustrate, those suffering from coronary artery disease may notice amplified chest discomfort if they are active in extreme heat due to the additional burdens of the body’s cooling systems.
Similarly, people with heart arrhythmias face a heightened risk of mortality during hot periods. A rise in temperature above 22 degrees correlates with a substantial increase in fatalities from arrhythmias, especially among women and those over 65.
Extreme temperatures additionally have a substantial impact on kidney function largely due to perspiration, which leads to reduced body fluid and altered electrolyte balance, making the kidneys work harder.
So, what steps can one take to minimise the risks associated with intense heat? Maintaining hydration by consuming ample fluids, preferably water rather than alcohol or fizzy beverages, is a good starting point. Evading direct sunlight exposure by finding refuge in shaded areas or air-conditioned spaces is also beneficial. Taking a lukewarm bath or shower can help cool you down. Applying a cool damp cloth to the nape of one’s neck can offer temporary relief. Heavy physical activity should be avoided and wearing loose clothing can help dissipate the layer of warm air next to the body more readily.