Letter Regarding Article by Law et al, “Headaches and the Treatment of Blood Pressure: Results From a Meta-Analysis of 94 Randomized Placebo-Controlled Trials With 24 000 Participants”
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To the Editor:
Is headache a cause or a consequence of hypertension? This apparently simple dilemma has not been answered over the last 100 years. All previous studies addressing this issue had important limitations, which left this as a medical impasse. The same seems to occur in a recent publication by Law et al1 in Circulation. After a judicious selection of 94 randomized trials with 4 classes of blood pressure–lowering drugs at fixed doses, the authors concluded that all classes reduce the prevalence of headache by one third, suggesting that high blood pressure is a cause of headache. Despite the robust study design, important points remain to be mentioned. First, the observation that blood pressure–lowering drugs prevent migraine is a well-established characteristic of many classes of antihypertensive drugs.2 Therefore, it is very likely that people in the interventional arm of the study would have fewer headaches than those in placebo arm. Second, none of the selected studies were designed to specifically evaluate the relationship between …