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Blood Pressure Drugs May Prevent Headaches

October 13, 2005

Blood pressure-lowering drugs may also help to prevent headache, according to recent findings by researchers in London.

The retrospective meta-analysis of data was published in the 11 October issue of Circulation, Journal of the American Heart Association and reported by MedPage Today on 11 October.

Researchers identified drugs in four classes-thiazides, beta-blockers, angiotensin converting enzyme (ACE) inhibitors, and angiotensin II receptor agonists-that reduced the incidence of headache. Data were derived from 94 randomized, placebo-controlled trials.

Study Methods and Results

Researchers examined 94 studies conducted from 1966 to 2001 in which fixed doses of blood pressure-lowering drugs were given and data on headaches were taken. All trials were double blind and lasted at least two weeks. Trials of calcium-channel blockers were excluded because drugs in this class are reputed to cause headache.

The data-review included 17,641 participants who received blood pressure-lowering drugs and 6,603 participants who received placebo. In those who received active treatment, systolic blood pressure decreased an average of 9.4 mm Hg and diastolic pressure decreased an average of 5.5 mm Hg.

In all groups receiving active blood pressure-lowering treatment, headache frequency was one-third lower (8%) than among the 6,603 participants who received placebo (12.4%). Additionally, treatment with any of the four classes of blood pressure-lowering drugs reduced the prevalence of headache.

"We are not saying that these drugs should be taken solely to prevent headaches, but this is a valuable associated benefit," said epidemiologist Malcolm Law, MSc, MBBS, at Queen Mary's School of Medicine and Dentistry of the University of London, according to MedPage Today.

However, Dr. Law stated that the data do not address the question of whether headaches disappear as blood pressure drops, or whether some other pharmacological mechanism in each drug class may explain the reduction in headache prevalence. He also noted that the link between blood pressure and headaches has been a "medical mystery for about 100 years," according to the MedPage Today report.

"The conclusion that the blood pressure-lowering drugs prevent headache is firm, and the conclusion that a higher blood pressure causes headache is likely but not corroborated by the observational studies (generally cross-sectional in design) on blood pressure and headache," Dr. Law and colleagues wrote in Circulation.

Dose-Response Link

Researchers observed a statistically significant dose-response relationship for diastolic pressure: in studies where diastolic pressure decreased by > 5 mm Hg, the reduction in headache prevalence was 13% greater. However, these data were derived from only one large trial. Omitting that trial's results makes the relationship between diastolic pressure decrease and headaches of marginal significance.

Posted: October 2005