Going for a long walk or participating in outdoor activities without having to bundle up to protect yourself from the elements is one of the great joys of summer.
But with temperatures forecast to rise later this month and the holiday season on the horizon, it’s a good time for us all to remember the very real dangers of heat stroke.
Far from being simply a matter of feeling hot, it is a hugely underestimated condition that can quickly cause irreversible damage to our organs and kill us.
Last year’s heatwave in Europe, for example, when temperatures exceeded 48°C, is estimated to have caused 60,000 deaths.
Heat stroke is an underestimated condition that can quickly cause irreversible damage to our organs and kill
And of course, the issue came to light recently following the tragic death of my esteemed colleague, Dr Michael Mosley, who was found collapsed on the Greek island of Symi, and although the exact cause is unknown, the scorching heat appears to have played a role.
And temperatures don’t have to be particularly high to pose a health risk: risks increase as temperatures rise above 25°C, especially if it’s humid and hot (more on this later). These risks start to increase within a few minutes of being exposed to high temperatures.
Some groups are particularly vulnerable, such as the elderly and people who are obese or have an infection, as these conditions hamper the body’s ability to regulate its temperature.
But the main risk factor is not being used to the heat. For example, if you suddenly go from dark, damp England to spend two weeks in a sun-filled paradise, you are at much greater risk than locals who have adapted to that climate.
But as someone who has treated life-threatening cases of heat stroke, I can tell you that there are ways to prevent it.
First, it is helpful to understand how heat can wreak such rapid and devastating havoc on the human body.
Our bodies are designed to function at around 37°C; enzymes and proteins so crucial to processes such as sending nerve signals around the body begin to break down when temperatures exceed this level.
The scorching heat is believed to have played a role in the death of Mail columnist Dr Michael Mosley, who collapsed on the Greek island of Symi last month.
This can have dire consequences, as cells die, toxic compounds are released, and organs literally begin to shut down.
To prevent this, our body has very sophisticated mechanisms to detect and regulate body temperature as close to 37°C as possible. This is why we sweat when it is hot, for example, because the sweat that evaporates from the skin has a cooling effect on the body.
But under some conditions, these mechanisms created to regulate our body temperature are not so effective.
For example, in hot and humid conditions, the air is already full of moisture, which prevents sweat from evaporating efficiently. And when sweat can’t evaporate, it can’t cool the body, leading to a dangerous rise in body temperature.
Intense exercise also generates its own body heat, so much so that the body cannot sweat enough to cool itself. If the exercise is prolonged and intense, such as running a marathon, you can get heat stroke in normal temperatures.
Often the first sign of heat stroke is confusion, as brain cells are most sensitive to temperature changes.
Other symptoms of heat stroke include dizziness, nausea, throbbing headache, hot, red, dry or clammy skin, rapid pulse, and fainting. These are all warning signs to look out for.
As cellular damage progresses, all of our organs can slowly stop functioning within minutes. But with effective treatment, this can be stopped and reversed.
Heat damage occurs through several mechanisms, and we are slowly uncovering this science to help us develop better treatments.
Often the first sign of heat stroke is confusion, as brain cells are most sensitive to temperature changes.
First, more blood is directed to the skin to help with sweating, so blood flow to key organs is reduced, which can lead to organ failure.
Muscle proteins begin to break down and release into the blood, damaging the kidneys.
Lack of fluid also contributes; it is possible to sweat up to 1.5 liters of fluid in an hour, which causes dehydration and a reduction in blood volume, making it more difficult to maintain adequate blood pressure.
All of this means that the heart needs to pump faster and harder to get blood to the skin, and we know that this can put a strain on the heart, as illustrated by a study published in the journal Annals of Internal Medicine last month.
Researchers in Canada examined 60 adults and found that for every 1.5°C increase in body temperature, blood flow to the heart doubled in younger, healthier patients.
But in those with heart disease, not only was there less increase in blood flow but they also began to suffer ischemic damage to the heart, which is a precursor to a heart attack.
Meanwhile, research published last year in the European Journal of Applied Physiology showed us that intestinal damage occurred as body temperature increased, with older people suffering more damage than younger people.
This group is thought to be particularly susceptible to intestinal damage, which in turn allows bacteria to leak into the bloodstream, potentially causing sepsis, a life-threatening reaction to infection.
Studies like this have led many of us in emergency medicine to begin giving intravenous antibiotics to those who are deeply ill from heat stroke.
In fact, as an emergency consultant, I have seen patients die tragically because treatment was not fast and effective enough.
Others have suffered significant damage and spent weeks in the hospital, while many who make a good physical recovery often have impaired cognitive function months after their heat injury.
And when it comes to effective treatments, the UK is at the forefront thanks to research by military doctors studying the effects of heat on armed forces personnel and marathon runners, who despite being fit are at risk of developing heat stroke due to the effects of extreme exertion in hot temperatures.
A life-saving innovation, originally developed for the Royal Marines, is a portable ‘ice water body bag’.
Designed by Dr. Ross Hemingway of the Navy’s Command Training Center, this device is used to wrap the body of a person suffering from heat stroke and immerse them in ice water. It can be so effective that no further treatment is necessary.
Tourists should consider soaking their hats in cold water before embarking on a day trip.
This is because we now understand how important it is to cool the body as quickly as possible before heat damage occurs.
It has been used successfully to treat 75 members of the armed forces who suffered from heat stroke, many of whom would otherwise undoubtedly have died.
I witnessed its effectiveness myself last year when, for the first time, it was instrumental in saving the life of a civilian – a competitor in the Brighton Marathon, where I was Medical Director.
Even if you’re not running a marathon or working out like a Marine, there are lessons we can all learn to protect ourselves from heat stroke.
These measures apply both at home and abroad, where it can be easy to underestimate the threat of extreme temperatures.
Firstly, if you are planning a holiday in hot conditions, acclimatising to the heat is essential, so spending time in a sauna before your holiday can be an incredibly effective preventative strategy.
And when you do visit, stay out of the sun, as temperatures reach 30°C, for example, and go out in the evenings, when it’s likely to be cooler.
In addition to sunscreen and a hat, wear light-colored clothing made of cooling fabrics (cotton is best) – these allow heat radiation and sweating.
Heat stroke goes hand in hand with dehydration, so we need to drink a lot more than usual. Make sure you never feel thirsty, that your urine is pale and clear, and avoid coffee and alcohol, as both are diuretics.
Do more to stay cool: Tour de France cyclists wear ice jackets before they set off – you could copy this by at least dipping your hat in cold water before you set off.
Heat stroke goes hand in hand with dehydration, so make sure you never feel thirsty.
Anti-inflammatory drugs such as Voltarol and ibuprofen should also be avoided whenever possible, as I have warned on these pages, since they can impair kidney function and damage the intestine, thus increasing the likelihood of heat stroke.
If you feel unwell or notice someone is confused by the heat, some simple first aid can help: get out of the sun, drink cool water and cool down.
If you don’t feel better, take a cold shower – you should feel better within five to ten minutes. If that’s not practical, put wet towels on yourself.
If it gets worse, the treatment is cold water immersion and you will need help with that – get help as soon as possible.
DO THIS…
Take up gardening – it may reduce your risk of depression, according to research from Anglia Ruskin University.
In a review of studies looking at physical activity as a mental health intervention, the greatest benefit was found to come from low- and moderate-intensity activities, such as gardening, golf, and walking, rather than high-intensity workouts.
“Moderate exercise improves mental health through biochemical reactions, whereas high-intensity exercise may worsen stress-related responses in some individuals,” the researchers said.