By: Thomas Pickering, MD, DPhil, FRCP, Director of Integrative and Behavioral Cardiology Program
of the Cardiovascular Institute at Mount Sinai School of Medicine, New York.

The decision to start treatment of hypertension involves judging the balance between the risks and benefits of treatment. The risks include the costs and potential side effects of medication, while the benefits are the prevention of heart disease and stroke. At first glance, it would seem that the benefits greatly outweigh the risks, but in practice it’s not so simple. The reason is that the majority of people who have hypertension will never have a problem from it, and also because treatment does not completely eliminate the risk: it only reduces the chance of having a heart attack by 20%, and a stroke by 50%.Thus many people will still have a heart attack or stroke even though they have had their blood pressure treated.

One way of looking at the benefit of being treated is to work out how many people would have to be treated to prevent one stroke or heart attack - an “event” which was the consequence of the high blood pressure. If everyone who had high blood pressure was destined to have an event if nothing was done, and if treating the blood pressure cut the risk of an event by half, you would on average need to treat two people to prevent one event. But if the risk of having an event was only ten per cent, nine out of ten people would not have an event whether or not their blood pressure was treated, and if treatment cut the risk in half, you would need to treat 20 people to prevent one event. So if you have hypertension, in the former case you have a 50% chance that going on treatment will do you some good (by preventing a stroke or heart attack), while in the latter case your chance of benefiting from treatment is only 5%. You might well decide that in the former situation you would decide to go on treatment, while in the latter, you would take your chances without being treated.

A recent survey conducted in England has thrown some light on what levels of risk people are prepared to accept before going on treatment. They were asked to decide if they would take drugs if one life could be saved for every 12, 33, 50, 100, or 250 people with high blood pressure who were treated for five years. Three groups of people took part in the survey: 39 consulting (attending) hospital physicians; 39 nurses working in primary care practices, 39 family practitioners, and 100 members of the general public.

The different groups gave very different answers: the consultant physicians said that they would recommend treatment if only 1 in 100 people benefited, the family practitioners said they would recommend it if 1 in 50 benefited, while the nurses and the public said they would only recommend it if 1 in 33 benefited. In other words, the physicians were more aggressive about recommendations for treatment than the patients.

Doctor’s comments

There is no right or wrong answer to the question that was posed here. The average benefit from treating hypertension in terms of lives saved is about 1 in 50, the same number as recommended by the family practitioners, but this number covers a wide spectrum of risk. Thus if your blood pressure is only raised a little your risk is only slightly higher than normal, and a large number of people with your level of pressure would need to be treated to save one life, whereas if your pressure was really high, the number would be much smaller, and the chances of your benefiting from treatment much greater.

The different answers given to the question are not what you might expect. Presumably the doctors looked at the question from the point of view of what they would recommend to their patients, whereas the members of the public who were surveyed viewed it from the point of view of being patients with hypertension, who would have to take the treatment themselves. Patients are becoming more involved in the decision making process in “gray” areas such as when blood pressure lowering treatment should be started, and these results suggest that they are likely to be less enthusiastic about starting treatment than their doctors.

Where it was published