While many of us revel in the hot summer sunshine, others are at risk of developing heat-related complications such as sunstroke and heatstroke. In this blog post we will outline how heat affects the body and look at some of the reasons why you could be at higher risk of becoming unwell in hot weather.
How the body copes with hot weather
Our bodies work to maintain consistent internal conditions, so that our cells and organs operate in optimal circumstances. To maintain our core temperature of around 37.5°C, our bodies regularly change the amount blood flow. When it’s hot, more blood flows close to the skin and we lose heat. This requires the heart to work harder to get the blood moving closer to the skin which can put it under strain.
This heat loss is helped by sweating. Evaporating sweat, or wet skin, can increase the amount of heat lost from the body by as much as 10 times, thereby reducing the strain on the heart. But we need to keep well hydrated to keep the sweat flowing.
Heat-related illness is a side effect of struggling with the heat
The extra work for the heart and the lungs combined with fluid and salt loss can cause a range of problems.
The combination of fluid loss/dehydration from sweating, with lower blood pressure as a result of all those extra dilated blood vessels, can lead to serious problems and can cause dizziness and fainting, or heat stroke. As dehydration worsens, people can experience heat cramps in their muscles, caused by the loss of crucial electrolytes that keep muscles functioning.
The combination of these symptoms, as well as sickness or nausea, headaches, heavy sweating and tiredness is called heat exhaustion.
Most people in good health will not suffer these symptoms if they drink plenty of water and seek out shade and cooler places, however, older people, young children, pregnant women and people with underlying heart or lung conditions are at more risk. This is why our advice focuses on reminding people to keep an eye on vulnerable friends, relatives and neighbours during a heatwave.
If someone is showing signs of heat exhaustion they need to be cooled down. The NHS advises that there are 4 things you can do to cool someone down and they should feel better within 30 minutes:
- move them to a cool place
- get them to lie down and raise their feet slightly
- get them to drink plenty of water. Sports or rehydration drinks are OK
- cool their skin – spray or sponge them with cool water and fan them. Cold packs around the armpits or neck are good too
Stay with them until they are better and call 999 if the person is:
- no better after 30 minutes
- still feel hot and dry
- not sweating even though they are too hot
- has a temperature that's risen to 40°C or above
- has rapid or shortness of breath or is confused, has a fit or loses consciousness
These are all signs of heatstroke which is a medical emergency and can kill.
It’s not just about heatstroke
It's important to understand that high temperatures can also worsen existing health conditions, sometimes with serious consequences.
People with conditions including, but not limited to, cardiovascular, respiratory, kidney problems or who are on certain medications may not just be vulnerable to heat in general, they may experience a worsening of their underlying illness during a heatwave. This happens because when the body tries to cool itself down, it puts additional strain on organs that may already be under pressure. For example, people with heart disease may find it harder to maintain adequate blood flow, leading to chest pain or even heart failure. Similarly, people with chronic obstructive pulmonary disease (COPD) or asthma may struggle to breathe as hot air, pollution, and dehydration combine to inflame the airways and reduce oxygen intake.
Those with kidney disease or diabetes are at increased risk of acute kidney injury when dehydrated in hot weather, as the kidneys become less effective at regulating body fluids.
Taking extra care when using certain medications
Medications commonly taken for chronic conditions, such as diuretics, beta-blockers, or drugs used to treat mental health issues (like antipsychotics and common antidepressants like SSRIs), can also alter the body’s ability to cool itself or keep fluids, making people even more susceptible to complications. It is important to understand how your medication affects your body’s response to heat and reread any instructions or speak to your doctor or pharmacist if you have any concerns.
In this way, hot weather doesn’t just present a risk of heat-related illness, but can act to worsen existing health conditions, an often overlooked but critical part of why some people may suffer more than others during heatwaves.
Keep hydrated, keep your home cool, keep yourself cool
Keeping hydrated is vital – drink plenty of fluids and avoid excess alcohol. Water, lower fat milks, and tea or coffee replace water lost through sweating and keep you cool.
When it’s hot outside, there are easy steps we can all take to reduce heat in our homes. Consider shading or covering windows, opening them on either side of the building when the air outside feels cooler (particularly at night) to improve air circulation, and using electric fans when temperatures are below 35°C, though avoid pointing them directly at your body to prevent dehydration. Reduce internal heat by switching off unnecessary lights and electrical equipment, as well as considering cooking during cooler parts of the day. Moving to cooler areas of your home for activities like sleeping can help.
During the day, it may be cooler to go to a park where there’s a breeze and some shade or air-conditioned public buildings such as libraries, community centres or places of worship, than stay in an overheated home.
Of course much of this advice is common sense, however we know heat-related mortality is occurring as we see in our annual Heat Mortality Monitoring Reports, and are projected to increase in the future as featured in the Health Effects of Climate Change report. The UK Climate Change Risk Assessment identifies risks to health, wellbeing and productivity from high temperatures as one of the greatest priorities for action for our country so it’s vital we all protect ourselves as well as our families and neighbours.