Use of an antihypertensive medication, specifically, a thiazide, beta-blocker, angiotensin-converting enzyme inhibitor, or angiotensin II receptor antagonist, is associated with a decrease of roughly one third in risk for headache, according to an article published in the October 11th issue of Circulation.

British researchers performed a meta-analysis of all randomized, placebo-controlled trials published between 1966 and 2001. In 94 trials, treatment with one of the four classes of antihypertensive was associated with an average reduction in blood pressure of 9.4 mmHg systolic and 5.5 mmHg diastolic pressure.

Analysis of self-reported problem data showed that 8 percent of treated patients reported headaches compared with 12.4 percent of placebo patients. Headache prevalence was significantly reduced in trials for each of the four drug classes, meaning that roughly 1 in 30 people received the unexpected benefit of headache prevention.

In 84 parallel group trials, 33 percent (on average) fewer treated patients than placebo patients reported headache. In the 10 crossover trials, 45 percent (on average) fewer treated patients than placebo patients reported headache. With no statistical difference between results for the two types of trial, the researchers considered the combined result to be valid.

Malcolm Law, an epidemiologist and lead author of the study, said “The question of whether higher blood pressure causes headache has been a ‘medical mystery’ for about 100 years. While our analysis leaves no reasonable doubt that four categories of blood-pressure-lowering drugs prevent headache, others found no connection between headaches in people with naturally higher blood pressure. Hence, the ‘medical mystery’ is not entirely resolved.”

Analysis also confirmed previous findings that antihypertensive medication can prevent migraine headaches.