Deaths from heart attacks and strokes rise during heat waves and again during the coldest months of the year. Two studies from the University of Innsbruck in Austria help explain why, by showing how the heart and blood vessels respond when the body is exposed to heat and to cold.
Why temperature matters for heart health
Your body works hard to keep its core temperature steady. In heat, it pushes blood toward the skin to release warmth. In cold, it narrows blood vessels near the skin to hold warmth in. Both responses put extra demands on the heart and can change blood pressure. For healthy people this is usually manageable, but for people with heart disease or high blood pressure, the added strain can be risky.
These questions are becoming more urgent. Heat waves are growing more frequent and intense, and rising energy costs mean some people may keep their homes colder in winter to save money.
The heat study
To mimic workers exposed to heat waves on the job, researchers followed seven men in a laboratory over nine consecutive workdays while they performed tasks similar to industrial work in hot conditions. The findings were published in Scientific Reports.
Even a relatively mild heat wave raised their core and skin temperatures and increased blood flow to the skin. That’s how the body cools itself while resting. The challenge comes when standing and working: the body must keep cooling itself while also maintaining enough blood pressure to supply the brain. That double demand strains the cardiovascular system and can lead to heat illness, fainting and, in people with heart disease, serious complications.
The cold study
The second study, published in Experimental Physiology, looked at mild cold. Researchers cooled the skin of 34 participants from its normal temperature of about 32–34°C (90–93°F) to about 27°C (81°F) using air at around 10°C (50°F). They tested two situations: cooling the whole body, and cooling only the face.
- Whole-body cooling raised blood pressure, mainly by narrowing blood vessels in the skin.
- Cooling only the face raised blood pressure by a similar amount, through a reflex that narrowed blood vessels throughout the skin of the whole body.
That finding suggests protecting your face from cold air may matter more than people realize.
How to protect your heart in the heat
- Stay hydrated and drink water before you feel thirsty.
- Avoid the hottest hours for strenuous activity, and take frequent breaks in the shade or air conditioning.
- Stand up slowly, especially after sitting or lying down, to avoid dizziness.
- Check your medications. Some blood pressure and heart medicines affect how your body handles heat. Ask your doctor or pharmacist.
- Know the signs of heat illness: heavy sweating, dizziness, nausea, confusion or fainting. Move to a cool place and seek help if symptoms are severe.
How to protect your heart in the cold
- Cover your face, head and hands with a scarf, hat and gloves.
- Dress in layers and keep your home warm enough, especially for older adults.
- Warm up before exertion. Shoveling snow and other sudden effort in the cold are known triggers for heart attacks.
- Monitor your blood pressure, which can run higher in winter.
Anyone with chest pain, shortness of breath or other warning signs of a heart attack should call emergency services right away, whatever the weather.
The bottom line
Both heat and cold make your heart work harder. Staying cool and hydrated in summer, and keeping warm with your face covered in winter, are simple ways to reduce that strain, especially if you have heart disease or high blood pressure.
This article is for general information and isn’t medical advice. Talk with your healthcare provider about your individual needs.
