Using a fan and wetting the skin reduces risk of deadly cardiac strain in hot and humid weather, but older people should avoid using fans in very hot and dry conditions. 

New collaborative research from the University of Sydney and the Montreal Heart Institute has looked at the efficacy of different, low-cost cooling strategies – such as electric fans with and without spraying water on the skin – for older adults, who are known to be at a heightened health risk during hot summer weather. 

The study exposed older participants with and without heart disease to two environments – one hot and humid (38°C and 60 per cent humidity) and the other very hot and dry (45°C and 15 per cent humidity); conditions chosen to represent the two most common heatwave extremes globally. 

The team found that in hot and humid conditions, fan use with and without skin wetting reduced heat-induced cardiac strain in older people. 

However, in the very hot and dry conditions, fan use had an adverse effect by tripling the increase in cardiac strain which could be fatal for someone with heart disease. 

This is because, although fans help sweat evaporate, in very hot and dry conditions the effect is small and counteracted by convection forcing more heat into the body. Instead, in these conditions, skin wetting used on its own was effective at reducing the work of the heart. 

Co-author of the study Dr Daniel Gagnon from the Montreal Heart Institute said: “Importantly, the study has shown that the weather conditions affect the type of cooling strategy that should be used – a vital piece of information that will help older people to stay safe in heatwaves.” 

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