The tragic death of my friend and colleague Dr Michael Mosley has highlighted how careful we all need to be about the risk of heatstroke – and especially the dangers we can face when away from our usual environment.
Heatstroke occurs when the body is unable to control what nature has determined is the best body temperature for our vital systems to operate normally. It is potentially lethal for people of all ages and fitness.
During heatwaves in the UK it is not uncommon to hear about the deaths of elderly or infirm housebound people who are unable to cool themselves adequately. But we also frequently hear of young army recruits on training exercises who succumb to heatstroke.
It can strike at speed and be fatal within a desperately short time, it pains me to say.
Dr Michael Mosley, 67, was found dead on Sunday morning having disappeared while walking in Greece on Wednesday
Dr Mosley succumbed to the heat on island of Symi - despite taking wise precautions such as carrying a bottle of water and an umbrella for shade
Heatstroke is where the body temperature rises above the normal range of 36C to 37.5C. It is due to failure of the body’s cooling mechanisms and is not the same as fever, which is caused by inflammation due to an infection, for instance.
With an infection, messages are sent by inflammatory molecules to the hypothalamus – the area in the brain that controls temperature (heat is the body’s way to kill off the pathogen causing the infection).
When body temperature rises above 40.5C and there’s no feverish illness, it is called hyperthermia, or heatstroke.
Our body heat is the result of internal metabolic processes – including digestion, muscle action and even brain function, which itself uses a lot of energy – and the effect of the heat around us.
Our method of cooling is sweating, where the water evaporates on the skin to bring temperatures down.
However, this fail-safe is ineffective in when it’s very humid, as the sweat doesn’t evaporate as effectively.
As the body temperature gets higher and higher, the central nervous system malfunctions.
As a result, fluid can accumulate in the lungs, making it hard to breathe and get enough oxygen. Lack of oxygen – but also the heat itself – can affect the heart muscle and the heart’s electrics can go awry, causing an abnormal heart rhythm.
Seizures are common, caused by the brain swelling, along with a number of potential effects throughout the nervous system (such as poor nerve function, affecting balance as well as muscle co-ordination, weakness and numbness in feet and legs).
Overheating also leads to kidney injury, liver damage and widespread blood-clotting throughout the body.
Essentially, heatstroke causes a total systemic breakdown, with survivors liable to experience long-term impairment.
Typically in young, healthy people it is caused by exercising, often unwisely, in conditions of high temperature and humidity.
But in the main, classic heatstroke affects those with an underlying medical condition that impairs their ability to cool down or renders them unable to escape the hot environment.
Risk factors include cardiovascular disease, neurological disorders, greater age, or even the unwise use of alcohol.
Those most likely affected are above the age of 70 – although we have all heard of tiny children left in cars in hot weather who have died of heatstroke, too.
Dr Michael Mosley was aware that he was going to be very hot – he took the precaution of carrying an umbrella to shield himself from the radiant heat of the sun and also carried a bottle of water. But the exertion he needed to hike back to where he was staying was perhaps underestimated.
The death of the much-loved TV doctor, pictured in newly released CCTV images of his final journey, shocked the country and highlighted the need to know what to do should heatstroke set in
Initially, those affected will feel weakened and shaky and, at some point, progressively exhausted and confused – the time between being aware that all was not well and confusion and disorientation may be very short, possibly only a few minutes, with no time for understanding the predicament you are in before things become desperately serious.
In such a state you might well collapse or fall, causing a head injury or other consequences.
In hot and humid conditions, none of us – whatever our age or health – can not afford to take the best possible precautions to avoid this.
I am just so desperately sad that this message follows the loss of our much loved Dr Michael Mosley.
