Summer heat and your heart—what’s the relationship?

After a cold winter and the ups and downs of spring, you may be eagerly anticipating summer and some fun in the sun.

However, all of that glorious heat comes with a few risks and dangers. You're probably familiar with the possibility of bug bites, sunburn and drowning, but did you know that excessive heat and humidity can pose a threat to your heart?

As you gear up for spending time at the beach (or pool) and getting back to those outdoor runs, here's what you need to know about how that summer heat can impact your heart and what you can do to stay safe.

What high temperatures and humidity do to your body and heart

When your body gets hot, your skin may flush and redden. This is caused by vasodilation (widening of your blood vessels) of the blood vessels that are in your skin.

Vasodilation is one way that your body can cool itself. By allowing more blood to flow through your skin, your body can shed heat by transferring it to the air surrounding your skin.

The tricky part with this, though, is that your heart has to work harder to keep your blood pressure steady when you are experiencing vasodilation.

"To keep your blood pressure stable, your heart has to beat both faster and harder. Studies show that for a young, healthy person, your heart works about 2.5 times harder when exposed to extreme heat," says Lawrence S. Mendelson, MD, a cardiologist at Bryn Mawr Hospital.

Certain medications (like beta blockers or calcium channel blockers) that treat heart disease, high blood pressure and arrhythmias can exacerbate the harmful effects of high temperatures on your body.

The other important way for your body to cool itself is by sweating. As your sweat hits the air and evaporates, it helps your body shed heat.

This gets more complicated with the high humidity that summer can bring. When it's humid, there's already a lot of moisture in the air and the sweat doesn't evaporate as readily from your skin. This makes sweating less effective at cooling you down, which keeps your body temperature high and your heart working hard.

Sweating can also lead to dehydration, especially if you aren't drinking enough fluids. Dehydration also puts extra strain on your heart.

If you're young, healthy and don't have any cardiac complications, your heart can usually deal with this extra work. However, if you are older or have heart disease or heart failure this increased workload can have some serious consequences.

Other risks associated with summer heat

Summer heat and heart issues are a two-way street. "Summer heat increases the workload on your heart, even if you don't have any cardiac complications," says Dr. Mendelson. "On the flip side, if you do have issues like heart disease or arrhythmias, you are at greater risk of heat-related illnesses and of more serious cardiac issues."

Heat-related illnesses include heat exhaustion and heat stroke. Both of these put stress on your heart—even if you are young and healthy. They become very dangerous if you are older or have any cardiac health issues.

Signs and symptoms of heat exhaustion include:

• Headache and dizziness
• Nausea and/or vomiting
• Weak and fast pulse
• Heavy sweating
• Skin that is pale and clammy

Signs and symptoms of heat stroke include:

• Headache and dizziness
• Very high body temperature (103°F or more)
• Confusion and/or fainting
• Strong, quick pulse
• Hot, dry skin or heavy sweating
• Heat stroke is a medical emergency and can be fatal. Although heat exhaustion is less extreme, it is still very dangerous.

Summer heat and particularly, heatwaves, are associated with increased hospitalizations due to hypertension, heart failure and arrhythmias. If you are an older adult, your risk of heat-related illnesses and heat-related cardiac issues is higher.

How to keep your heart—and yourself—safe in the summer

Keeping active and spending time outside this summer are great ways to stay fit and healthy—as long as you are aware of the risks and take steps to reduce their likelihood.

Stay safe this summer and take care of your heart by:

• Staying hydrated: Aim to drink about 8 oz of water per 15 to 20 minutes spent outside on a hot day.
• Dressing appropriately: Wear light-colored and loose clothing like cotton to help you stay cool.
• Keeping cool: Staying in an air-conditioned area or even using a fan can help your body's temperature stay at safe levels and ease the workload for your heart. This is especially important during the hours when the sun is the strongest, generally from about noon to 3 p.m.
• Continuing to take your prescribed heart medications: Unless told otherwise by your healthcare provider, take your medications as prescribed. Talk to your healthcare provider if you have any concerns about how the summer heat might interfere with your medications.

By staying mindful of how the heat can impact your heart and taking proper precautions, you can feel ready to welcome summer with open arms.

Next steps:

Make an appointment with Lawrence S. Mendelson, MD
Learn more about cardiovascular care at Main Line Health
What young athletes should know about their heart health and sudden cardiac arrest