Hot weather can be hard on the body – and may even worsen some health conditions

By Adam Taylor, Lancaster University

The current weather forecast suggests summer might finally have arrived, as the UK’s first heat health alert of the year has been issued.

While many may be rejoicing after the UK’s miserable spring, it’s worth remembering that hot temperatures can be dangerous. Heat stroke is a risk for anyone – though the elderly and people with underlying health conditions are particularly at risk.

Certain health conditions can also be made worse when it’s hot outside. So if you’re someone who has a heart, lung, kidney or metabolic condition, it’s worth being extra careful during the hot weather.

Heart conditions

Many cardiac conditions become worse during hot spells because the cardiovascular system has to work harder than usual. This is because it plays an important role in the body’s built-in cooling processes. The heart helps move heat away from vital systems, and brings blood to the skin’s surface in order to cool it down.

As such, the heart works much harder during hot weather – beating up to ten times more per minute for every 1°C temperature increase. Blood flow to the skin is also increased to between six to eight litres per minute, which also spikes the heart rate in order to try and cool the body.

People of course also sweat more during hot weather so the body can cool itself. But if they don’t drink enough fluid, this results in thicker blood. This, too, means the heart has to work harder.

All of these changes can worsen heart condition symptoms.

For example, people with heart failure may find hot weather particularly challenging. Cooling processes such as sweating and vasodilation (widening of the blood vessels) are impaired by this condition. This makes the heart work harder. People with coronary artery disease may also experience chest pain (angina) if they exert themselves during the hot weather, due to the added pressure of these cooling processes.

People with heart arrhythmias, particularly atrial fibrillation, are at increased risk of death during hot weather.

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