Hikers Beware: Blood Pressure Can Rise at High Altitudes

Visiting high-altitude locations may be dangerous for people with high blood pressure or certain heart conditions, according to a new report from the American Heart Association that offers guidance about engaging in recreational activities in mountainous regions.

Altitude exposure is known to cause an increase in adrenergic activity, blood pressure (BP) and heart rate (HR) in resting conditions.

Spending time at high altitudes may raise your blood pressure, according to a growing body of evidence, and these spikes may be particularly dangerous for people with existing heart disease.

In one study, researchers found that blood pressure steadily increased as climbers ascended Mount Everest, the highest mountain on Earth. What's more, telmisartan, a drug widely used to treat high blood pressure, no longer worked once climbers reached a certain altitude.

How High Is Too High?

High blood pressure, known as hypertension, is considered to be 130 millimeters of mercury or higher for the systolic blood pressure or 80 and higher for diastolic pressure, according to the American Heart Association. Often called the "silent killer" because there are sometimes no obvious symptoms until it is too late, high blood pressure is a major risk factor for heart attacks and strokes.

Several groups of medical experts have issued recommendations on the risks of higher altitudes for people with existing heart conditions. They report that altitudes that are 8,200 feet above sea level may increase blood pressure and heart rate and that people with preexisting heart disease may be even more vulnerable in the face of these changes.

Both the sympathetic nervous system and renin-angiotensin system can be activated at high altitudes.

It's a double whammy, he explains. The sympathetic nervous system can stimulate the release of the stress hormone adrenaline, which speeds up the heart rate and blood pressure levels. The renin-angiotensin system stimulates production of angiotensin II, which constricts blood vessels, causing them to narrow.

Blood Pressure and Altitude

Blood pressure changes aren't the only risk of spending time at higher altitudes. So-called mountain or altitude sickness is marked by headache, nausea, vomiting and lightheadedness. It occurs because your body doesn't have enough time to adapt to the lower air pressure and lower oxygen levels in the air at high altitudes, altitude sickness can cause you to become short of breath even at rest and make it difficult to walk.

If you will be spending time at higher altitudes, they recommend that you:

Drink at least 3 to 4 quarts of water a day.
Don't smoke, drink alcohol or take any depressant drugs.
Ask your doctor about a medication called Diamox (acetazolamide) to help you acclimate to the higher ground.
Know the early signs and symptoms of altitude sickness and get help.
Ascend gradually.
Continue drinking coffee if it is part of your day-to-day routine.
Exercise only mildly for the first 48 hours.

The good news is that mild symptoms of altitude sickness improve once you return to a lower ground, the Cleveland Clinic states.