• headache
• hypertension
• migraine

Patients often tell their physicians, “I know when my blood pressure is high because I get a headache”. The relation of headache to hypertension has been debated in the medical literature for almost a century. Janeway observed it in a large clinical study of hypertensive patients (systolic blood pressure > 160 mm Hg) in 1913.¹ He described the “typical” hypertensive headache as non-migrainous, present upon awakening and resolving during the morning. However, his illustrative case histories are somewhat misleading because they all had malignant hypertension and systolic pressures > 230 mm Hg. Additionally, one patient was likely in analgesic rebound.

There are several reasons why the “hypertension headache” misperception persists: hypertension may be an epiphenomenon of acute pain, headache is associated with hypertensive encephalopathy as a manifestation of increased intracranial pressure, and headache is a side effect of some antihypertensive treatments. Conversely, many of the antihypertensive medications are also effective for headache prevention, so the risk of concurrent headache may be low unless the influence of treatment is considered.

The Physicians' Health Study prospectively examined 22 701 American male physicians aged 40–84 years, who were randomly assigned to receive daily aspirin, β carotene, both agents, or placebo.² Analysis of various risk factors for cerebrovascular disease found no difference in the percentage of patients with a history of hypertension between the migraine and the non-migraine groups. Additionally, no difference in risk factors was found between physicians with non-migrainous headaches and those with no headaches.

The paper by Hagen et al (this issue pp 463–466)³ lends definitive clarity to the issue. In their prospective study spanning 13 years of 22 685 adults in Nord-Trøndelag County, Norway, patients' blood pressure was measured interictally and they provided information regarding headaches and the use of pain relieving medications. Patients were subdivided into those with migrainous and those with non-migrainous headache based on modified International Headache Society criteria for migraine. Contrary to popular belief, high systolic blood pressure at baseline was associated with low headache prevalence 11 years later. This was not related to antihypertensive medication treatment. A similar effect was observed in women with migraine.

Their study is relevant because it is a cross sectional study of a large unselected population. Hypertension is more common in men but women have a higher incidence of headaches. Both women (10 698) and men (11 987) participated in HUNT-1 and HUNT-2 (Nord-Trøndelag Health Survey), supporting the conclusions in both sexes. Generalisation of the results was addressed by the authors in other reports.⁴ Race and geographic region contribute to variations in the prevalence of headache and hypertension. Participants in the HUNT studies were a homogeneous white population. Thus, the applicability of the results to other populations, such as African Americans, who have a higher prevalence of hypertension, is uncertain.