A Cardiologist’s Guide To Hot Weather And Your Heart
As summer brings brighter days and warmer temperatures across the UK, many of us look forward to spending more time outdoors. While the sunshine is a welcome boost for our wellbeing, warmer spells mean our bodies have to work a little harder to keep us comfortable.
In fact, a landmark study published in the journal Circulation analysed over 202,000 heart attack deaths and revealed that prolonged heatwaves can cause the risk of a fatal heart attack to shoot up by 74% in older adults – a risk that nearly doubles when extreme heat is combined with summer air pollution.
By understanding how the heat interacts with our cardiovascular system, we can navigate the weather safely, confidently and with more peace of mind. In light of the recent record-breaking heatwaves, we explore the impact of hot weather on the heart, and what you can do to maintain your heart health as the mercury rises.
How Does Hot Weather Affect The Heart?
To keep your core body temperature stable when the thermostat rises, your body relies on its natural cooling mechanism: sweating. However, to push that heat out of your body, your blood vessels dilate (widen), and your heart has to pump faster and harder to circulate blood towards the surface of your skin.
In fact, during a hot and humid day, the human heart can circulate two to four times as much blood each minute compared to a cool day.
Consequently, for every 0.5℃ your body’s internal core temperature rises, your heart automatically beats an extra 10 times per minute to cool you down. In healthy, resting adults during a summer heatwave, this typically translates to an expected increase in resting heart rate of 10 to 30 beats per minute.
This natural process places an immense workload on your cardiovascular system, but as Dr Ravi Assomull, Consultant Cardiologist at One Heart Clinic, explains, the danger isn’t just the extra pumping power required – it is a combination of hidden internal stressors.
“It’s likely a combination of inflammation and increased blood thickening, which leads to coagulation and platelet activation,” says Dr. Assomull. “The other key factor is dehydration, which puts stress on the body. That stress increases heart rate and blood pressure, and all of that strain additively will increase your risk of a heart attack or strokes.”
When you become dehydrated through sweating, your blood volume drops, making your blood thicker and more likely to clot, while simultaneously causing your blood pressure to fluctuate. For most healthy people, this is a minor adjustment the body handles without an issue. But if you have an underlying heart condition, this extra physical strain can quickly escalate from feeling faint, dizzy or excessively fatigued into a much more serious cardiovascular event.
This extreme heat is no longer a one-off summer event – it is something that is going to keep recurring year after year. Because of this, patients with established heart conditions need to be proactive. Now is the time to speak to your clinician to personalise your medical regimen, especially if you are on medications like diuretics. Additionally, while air conditioning is part and parcel of everyday life in hotter countries, it may be time for UK patients to seriously consider installing it at home to stay safe.
— Dr Ravi Assomull, Consultant Cardiologist at One Heart Clinic
Who Is Most At Risk During A Heatwave?
While everyone feels the effects of a humid summer day, certain individuals should take a slightly more mindful approach to the heat:
- Older adults: As we age, our bodies become slightly less efficient at regulating internal temperatures and sensing dehydration.
- Those with existing conditions: Individuals living with conditions like coronary artery disease, heart failure, or high blood pressure need to be more cautious, as their cardiovascular systems have less reserve capacity for the extra workload.
- People taking specific medications: Certain treatments, such as diuretics (water tablets) or blood pressure medications, can alter how your body handles fluids and expands blood vessels, making you more prone to sudden drops in blood pressure.
Managing medications during extreme heat is one of the most critical – yet frequently overlooked – vulnerabilities for heart patients. Dr Assomull highlights a major gap in standard patient care during the hotter months:
“Patients will take medication because they’re told to comply with them, but there are exceptions. If you are in hot weather and losing a lot more water through sweat, people on diuretics or ACE inhibitors – which can affect the kidneys – may need to omit or reduce their doses. This is something patients rarely think to reach out to their cardiologist or GP about, and GPs don’t necessarily phone up to suggest a medication review for the summer months.”
With extreme heatwaves now becoming a regular fixture of British and European summers, managing these “insensible fluid losses” (the sweat and moisture your body loses without you realising it) is vital. If you are taking regular cardiac medications, it is highly recommended to have a proactive conversation with your doctor about how to safely manage your dosages during hotter weather.
Lifestyle Tips To Protect Your Heart
Keeping your heart safe in hot weather doesn’t mean staying locked indoors. It is all about pacing yourself and choosing smart, simple habits:
Hydrate wisely
For every 1% of body weight you lose in sweat, your heart rate spikes by roughly 7 beats per minute, independent of how hot it actually is outside. Therefore, during a heatwave, you should drink plenty of water throughout the day, even if you don’t feel intensely thirsty. Light herbal teas, diluted squashes, and water-rich foods like cucumber or watermelon are fantastic options. If you have been advised by a doctor to restrict your fluid intake, speak to your care team about how best to manage your medication and hydration.
Time your outings
Avoid the peak heat of the day, typically between 11:00 am and 3:00 pm. Save gardening, walks, or errands for the cooler mornings or evenings.
Exercise with awareness
If you feel you can exercise, avoid doing so during the hottest time of the day. Hydrate well, and keep to shaded areas if you are exercising outdoors. If you start to feel dizzy, nauseous, or excessively fatigued, or if you develop a headache, stop exercising immediately.
Keep your home cool
Close curtains or blinds on windows that face the sun during the day to block out the heat, and open windows in the evening when the outside air cools down.
Dress comfortably
Choose loose-fitting, lightweight clothing made of breathable natural fibres like cotton or linen, which allow air to circulate and cool the skin.
When To Seek Medical Advice
For individuals with established cardiac disease, it is important to understand that you are at risk well before any adverse symptoms even begin to emerge. Do not wait to feel unwell before taking action – extreme heat places a silent, immediate strain on your cardiovascular system.
By staying proactive and monitoring yourself closely, you can catch early warning signs. It is important to know the difference between standard heat fatigue and symptoms that require professional medical attention.
Please contact a doctor or seek immediate care if you or someone you know experiences:
- Massive changes in blood pressure or heart rate
- A sudden, painful chest tightness or pressure
- Breathlessness that does not improve when you rest in a cool place
- Dizziness, confusion, or fainting spells
- Severe muscle cramps, nausea, or vomiting alongside heavily flushed, dry skin
Your Peace Of Mind This Summer
“The warmest months often serve as a gentle reminder of how important our physical resilience truly is. If the recent hot weather has left you feeling unusually fatigued, or if you simply want to make sure your cardiovascular health is exactly where it needs to be, a proactive check-up can provide immense reassurance.”
At One Heart Clinic, our Cardiovascular Risk Package is designed to give you an exceptionally thorough, clear, and comforting overview of your heart health.
Our friendly team would be delighted to help you find out more about this package or book a consultation. Click to book online, or call 020 3983 8001.
