WHAT HAPPENS TO YOUR BODY WHEN  IT OVER HEATS?

Age, health and where you live in a city can increase your risk of dying.

Many elderly people don't rehydrate as often as they should and may also be on dehydrating medications, which could contribute to their higher risk of serious illness or death during heat waves. 

As the temperature, with humidity, felt like more than 40 C in southern Quebec this week, health officials reported that many of the more than 50 heat-related deaths were people over 65, or had health problems, or both.

Age and chronic health issues are both frequently cited as risk factors during heat waves, but why is this so?  

Studying the science of heat's effect on the human body has been a 30-year pursuit for Glen Kenny, a professor and research chair in environmental physiology at the University of Ottawa. He's conducted hundreds of trials measuring its effects on younger versus older people.  His studies have shown that if seniors are exposed to temperatures of 44 C over a few hours, they aren't able to restore their body's "heat balance" as quickly as younger adults. That's partly because the body produces less sweat as people age — and sweating is one of the main ways we get rid of excess heat.

Prof. Glen Kenny of the University of Ottawa, says seniors aren't able to restore their body's 'heat balance' during extreme temperatures and high humidity. (University of Ottawa)That's why "the humidity is really what is the killer" in heat waves like Quebec's. The more moisture in the air, the less sweat can evaporate from our skin.

Another factor that can put many elderly people at risk is reduced thermal sensation which makes them the feeling hot. 

"They're more likely to experience dangerous levels of hyperthermia [overheating] before they actually respond or react to it. And by then it often too late.

Older people may not feel thirsty until they're already dehydrated. In addition, they are also more likely to be taking medications — many of which can be dehydrating. Alas, because I suffered from an attack of congestive heart failure years ago which hospitalized me for a month,  I have been prescribed a drug which reduces the amount of fluid in my body which in variously  makes me thirsty much of the time. I am often taking fluids which are always in my reach.

Water is key to maintaining the right volume of blood in the body. When the volume decreases, our blood pressure decreases, and that can lead to people passing out and injuring themselves when they fall.  

Low blood volume also puts additional stress on the heart, making it work harder to get blood throughout the body. That puts seniors in a dangerous situation — especially if they already have heart or circulation problems. 

The main thing that elderly people will experience is cardiovascular distress because of the burden placed on their cardiovascular system.  

Diabetes, for example, can hamper blood flow to the skin.   Another significant threat posed by very high temperatures and humidity is heat exhaustion — with the most extreme cases progressing to heat stroke.  

In 1954 while I was serving in the Canadian navy, I was standing guard duty alone at a guard post on an extremely hot day when I felt faint. I was suffering from heat stroke. I phoned the base headquarters and was given permission to walk to the base hospital. I waited for an hour in the waiting room and when they discovered that my temperature was as high as 105 degrees Fahrenheit, the doctor was shocked that I was still alive. I was put on a gurney and wheeled into a room.  I then went into shock. I survived but was in the hospital for two weeks.

People who are elderly and in frail health (like I am) are more prone to heat stroke, said Dr. Steven Rhee, medical director of the emergency department at St. Joseph's Hospital in Toronto, because they don't have the same endurance or ability to bounce back as younger, healthy patients once heat exhaustion sets in. I didn’t bounce back when I had heat stroke in 1954 but I did gradually recover.

During extreme heat waves, Rhee said that he sees a huge range of heat-related symptoms in the emergency department. They range from the early phases of heat exhaustion, such as feeling tired and mildly dehydrated, to feeling nauseated or faint.

When people reach a core temperature of above 40 C (104 F) and experience the most serious symptoms — including passing out, stopping sweating and low blood pressure — they have life-threatening heat stroke.

It's not something that happens in minutes. It's usually takes hours of exposure to heat. Basically the body is shutting down at that point because the body loses the ability to circulate and cool itself down, evaporate our own sweat from our body’s surface.

Heat stroke also affects the central nervous system, and the body's organs stop working. That happens because if the body remains at a dangerously elevated core temperature for a certain period of time, cells die.

When warning people about the dangers of heat waves, public health officials need to focus not only on the temperature and humidity outside, but be aware of the humidity and temperature inside people's homes. 

Indoor temperatures can vary widely within the same city with people in certain types of homes in specific neighbourhoods suffering hotter and more humid conditions than others. 

Even from one block to another, there may be the same population group at significantly different risks of experiencing heat-related deaths.  That's because of a phenomenon known as "heat islands," which occur in densely-populated urban areas. 

Cities tend to be hotter than surrounding rural communities, partly because they don't get the same cooling effect when the sun goes down. Communities close to a large body of water there is a cooling effect going on.  There are fewer open spaces in cities, and in areas that are heat islands, the radiation from the sun gets absorbed by asphalt or buildings during the day, keeping the environment hot at night. 

The types of buildings people live in can also contribute to dangerously high heat inside. Low-rise apartment buildings located close to each other can trap heat, while areas dominated by high-rises might have better air flow between them, Older buildings may also allow more heat to get in from the outside. 

In Quebec, public health officials said people who died didn't have air conditioning. The risk of heat-related death rises the longer people are inside their hot and humid apartments or homes. It's that sustained temperature elevation that's really the problem over successive days.  

That's why it's so important for people — especially seniors — to seek air conditioned spaces, such as public cooling centres, as soon as any sign of heat stress appears. Many people will flock to public buildings such as libraries that are air-conditioned.

Older adults tend to try to "tough things out which is stupid. If their homes are hot and they more tired or thirsty than usual, they need to get help and stay hydrated and cool.

Unfortunately, often many older people die in front of a fan when  they don’t have air-conditioning in their homes. That is because of the adverse effects of the electric fans because it is said when temperatures are above 35 degree Celsius (95 degree Fahrenheit) the fan may lead to an increase in heat gain. Though there are no concrete evidence, it is believed that a fan that blows out excessive hot air on an already hot body, can increase one’s chances of dehydration and other health problems. If they fall asleep while sitting in front of the fan, they won’t be aware of the danger they are facing.                                                    

Obviously, suffering from heat exhaustion is one of the ravages of being old. Unfortunately, the only way to escape that particular ravage of being old is to die when you are young. Alas, I didn’t have that advantage because as my wife tells her friends, “Only the good people die when they are young.” She says I am so bad, I will outlive God. However as you may have surmised by that particular statement; she tends to exaggerate. I have told her a million times if I have told her once not to exaggerate.

In 1995, I was invited by the United Nations to give a speech at a UN Crime Conference being held in Cairo. After I gave my speech, my wife and I took an overnight train to the city of Luxor that is 504 kilometres (313 miles) south of Cairo. It borders the east side of the Nile River. It is classed as the largest outdoor museum because of the temples in the area of that city.  We were there in May of that year and the temperature in that part of Egypt was extremely high. The temperature in May of that year was 107  degrees Fahrenheit (41.6 Celsius). As the Egyptologist was reading the ancient hieroglyphic script at the top of the temple with the hot sun shining on us, I was beginning to feel faint. So I told the Egyptologist that I too can read hieroglyphic script. I then began moving my finger at the scrip where he left off and in doing so, I said, “Tourists are melting in the sun and need immediate shade.” He looked at the script and with a big smile on his face, he said, “You are really good at reading this ancient hieroglyphic script. That is exactly what it says, Jet’s go to the administration building where the air-conditioning is on full power.”

Standing outside the temple in the sun when the temperature was as high as it was then, increased the risk of our body temperatures increasing at least to 105 degrees Fahrenheit and perhaps even more which would have been fatal to us.