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.

Headache is the commonest reported symptom in people with hypertension, but it is also very common in those with normal blood pressure. There is also some evidence that lowering the blood pressure may make it less frequent.

The new class of blood pressure-lowering drugs, the angiotensin receptor blockers, has been found to be generally associated with fewer side effects than some of the older drugs. An analysis of seven studies with one of them, irbesartan (brand name Avapro), has looked at the effects of treatment on the frequency of headaches. The studies were all double blind, randomized, placebo-controlled studies. What this means is that patients with hypertension were randomly allocated to be treated with either placebo (inert pills) or irbesartan for a period of four to 12 weeks. During the study, neither the patients nor the doctors knew which type of pill they were taking (hence the term “double blind”). During the course of all the studies, patients were asked at regular intervals about any symptoms they were experiencing.

In the patients who took placebo during the study, there was not much connection between the height of the blood pressure and the occurrence of headaches: for systolic pressure, there was none, while for diastolic pressure, there was a tendency for people with higher pressures to have more frequent headaches. They were reported by 19% of people with diastolic pressure below 90 mmHg, and 27% of people with a pressure of 100 or more. Patients who were treated with irbesartan reported less headache than patients receiving a placebo, but the differences were not very big - 17% of patients treated with irbesartan reported headaches, versus 22% of those treated with placebo.

Doctor’s comments

The message of this study is that there is a connection between high blood pressure and headaches, on the grounds that people with higher blood pressure to begin with had more headaches than those with lower pressures, and that treatment with a blood pressure-lowering drug reduced the headaches. The findings were strong in the terms of statistical significance. That is, they are very unlikely to be from chance, which may be explained by the large number of patients who were included in the study. However, when the extent of the differences is looked at, it is not so impressive. Thus treating the hypertension with irbesartan lowered the headache rate from 22% to 17% - a difference of 5%. So out every 100 patients with hypertension, five would expect to have their headaches improved by treating the hypertension, while in 17 others, the headaches would be unaffected by changing the blood pressure. Another study that we posted recently showed that short-term changes of blood pressure do not affect headache, so the exact reason why high blood pressure causes headache is not clear. There is no particular reason to think that the drug used in this study is any more effective at controlling headaches than any other blood pressure-lowering drug.

Where it was published