Cold water and High Blood Pressure

What does cold-water immersion do to your blood pressure?

On immersion in cold water:

• Your heart rate goes up: In those people not acclimatised to cold water, this occurs within 2-3 seconds and is an increase of around 20 beats/minute.
• Your blood pressure rises: in one study average blood pressures went from 130/76mmHg (fairly normal) to 175/95mmHg (would need treatment though unlikely to cause any immediate complications).

These responses are significantly reduced in people who regularly swim in cold water.  Although maximal adaptation probably occurs after several immersions in 10-14˚C water, there is significant adaptation even at 18˚C i.e. the temperature of the sea down here in Brighton during the summer.

There is therefore very little risk for someone with a normal blood pressure- and this includes people with well-controlled hypertension.

Problems are only likely to occur in those with coronary artery disease because the increased heart rate means less blood goes to the muscle of the heart itself while, at the same time, more strain is being put on the heart.

The only other group of people at increased risk are those with abnormalities in the arteries that take blood to the brain.  These are very uncommon and you are unlikely to know anything about it even if you do have this condition.

So what are the risks?

The risk of swimming outdoors to people with treated hypertension is probably no different to that of those with normal blood pressure.

The risks are even lower if people are acclimatised to swimming in the cold.  My advice would therefore be to start your outdoor swimming when the water is at its warmest.

And, of course, it’s important to put it all in perspective.  The chances are that the tiny risks are significantly outweighed by the benefits of exercise and cold-adaptation which include better mood and better metabolism (especially with regard to the way the body handles sugar). There is even evidence to support the theory that cold adaptation-which can be achieved through open water swimming-may actually reduce the overall risk of a heart attack.

Remember that this is only a very general overview so, if you have any concerns about your personal situation, please visit your own doctor before throwing yourself in the sea.