Effects of hot weather, humidity on blood pressure, heart

Weather can play a role in triggering certain health problems. High temperatures and high humidity are two factors that can cause serious health consequences for people with high blood pressure and heart disease.

In summer weather, blood pressure can be affected by the body's attempts to radiate heat. High temperatures and high humidity can cause more blood flow to the skin. This causes the heart to beat faster while circulating twice as much blood per minute than on a normal day.

The greatest risks are when the temperature is above 70 degrees and the humidity is more than 70%. The higher the humidity, the more moisture in the air. Some people are at higher risk of being affected by humidity, including those who are over age 50, overweight, or have heart, lung or kidney conditions.

Heat and sweating also can lower the amount of fluid in the body, which can reduce blood volume and lead to dehydration. This can interfere with the body's ability to cool off and may create strain on the heart.

When the body loses more fluid than is taken in, the body may not have enough water or other fluids to carry out its normal functions. Anyone can become dehydrated, and it can lead to serious complications for people at greater risk due to age, chronic conditions or outdoor activity like work or exercise.

Other risk factors include:

• Adults with heart, lung and kidney problems
• Adults who take diuretics, sedatives or blood pressure medication
• People who follow a low-salt or low-sodium diet
• People who have a circulatory disease or problems with circulation

People with a history of high blood pressure should monitor their blood pressure during heat waves. They also should drink plenty of fluids to stay hydrated, avoid the midday heat, eat a healthy diet, apply sunscreen if outdoors and wear a hat. In most cases, when in doubt, stay inside a cool environment in your home.

Warning signs that your body isn't keeping up with the heat include:

• Cold, clammy skin
• Confusion
• Dizziness
• Disorientation
• Rapid pulse
• Excessive sweating or an inability to sweat
• Fatigue
• Headache
• Muscle cramps or spasms
• Nausea
• Swelling in your arms or legs

If you or a loved one are exhibiting more than one or two of these symptoms, seek medical intervention immediately.

Heat and medication

Just like you should find ways to keep your body cool during high temperatures, you also should store your medications properly so they're not exposed to extreme heat. Some medications can become degraded during temperature changes, including insulin used for diabetes management.

Store medication in a cool, dry place. If you store medications in a bathroom with a shower, on a window ledge or in a vehicle, keep the medication in the original container to help seal out excess heat and moisture.

Some medications can affect your ability to stay hydrated and respond to high temperatures, including those used to:

• Treat high blood pressure, including beta blockers and diuretics
• Reduce allergy symptoms, like antihistamines or decongestants
• Decrease psychiatric symptoms, such as antipsychotics

Talk with your care team about concerns you may have regarding how your body responds to specific medications during high temperatures.

By Mayo Clinic Health System staff