Q
: Are people from tropical countries also at risk of heat-related illness ?
A
: People from tropical countries are at risk from heatrelated illness as anyone else . However , they are likely to be better adapted . Malaysia is a tropical country , so heat is an environmental hazard that we ’ re adapted to , as opposed to someone living in a more temperate region and visiting or moving here .
Prolonged heat exposure can have a great effect on our wellbeing . Preparation is the best response . Wear the correct clothing . Use sunblock . Be sure to hydrate well and often . In spite of the best preparation , be aware of the danger signs . Dizziness , difficulty breathing , and shivering even when it ’ s hot out are an indication that things are not going the way they should . When these occur , take corrective action . Get in the shade , hydrate , and even dousing yourself with a bottle of cold water is a quick way to cool down before things get too bad .
We all have the same physiology . Adaptation however takes time . If you send somebody from Malaysia to Minnesota in winter , they won ’ t be able to adapt to the cold very quickly . Similarly , if an Eskimo moves to the tropics , he will need some time to acclimatise .
Q
: What happens to the body during prolonged exposure to heat ?
A
: When exposed to prolonged heat , our bodies will first thermoregulate . This means that we cope with the heat we ’ re exposed to by sweating — our sweat evaporates and our body temperature comes down as a result . We also start to hyperventilate , we breathe faster which evaporates water in our lungs and this brings down our core temperature too . We do get to the point where we are no longer able to thermoregulate . That is when we become dehydrated . This leads in turn to hypovolaemia , a situation where we have very little circulating blood volume . At this point , our ability to compensate to heat fails . Typically the blood pressure then drops to a point that we begin to lose consciousness as well .
There is no established point when this breaking point happens . It is highly variable but depends on how fit you are , how hydrated you are , how much fluid you had to start off with , and how much heat you ’ ve been exposed to . It also depends on how old you are . For example , there have been cases when children left in bassinets in parked cars have died because their ability to withstand heat is much reduced as compared to an adult .
Q
: Do underlying conditions pose greater risk from prolonged heat exposure ?
A
: Patients with heart disease , high blood pressure , or uncontrolled diabetes are more susceptible to heat-related illness because they tend to reach their tipping point earlier than healthier patients . If you have heart disease , your heart ’ s ability to withstand extremes of heat is rather limited . If you have a leaking heart valve , for example , you likely to be unable to compensate as well as a healthy adult , so any deviation from that norm tips you over faster . If you have blockages in the arteries that supply the heart and if your blood pressure drops too much , you ’ ll be at risk of a heart attack . This is likewise for patients with uncontrolled diabetes and those with respiratory illnesses , where you can ’ t oxygenate as well as someone who does not have these underlying conditions .
Q
: Does harm from heat exposure build up over time ?
A
: Additive harm from repeated exposure to heat does not occur . An exception to this is perhaps exposure to environmental radiation . Radiation does build up over time . For example , if I were to spend seven hours a day , out in the sun , over two years , then my risk of developing squamous cell cancer is much higher because of the accumulated radiation . But when it comes to heat , there ’ s no such risk . Once you hydrate and get your body temperature down again , you ’ ll be able to do it tomorrow .
Dr Alwi Mohamed Yunus
Dr Alwi Mohamed Yunus is head of cardiothoracic surgery at IJN , Malaysia ’ s national heart institute , in Kuala Lumpur .
GlobalHealthAsiaPacific . com OCTOBER 2021
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