Elevated blood pressure (BP) and headache have long been linked in the medical literature, although data on association are conflicting. We used previously collected data to address these related aims: (1) using the National Hospital Ambulatory Medical Care Survey (NHAMCS), we determined whether elevated BP is more likely in patients who present to an emergency department (ED) with headache than in patients who present with other complaints; (2) using data collected in 3 ED-based migraine clinical trials, we determined the association between improvement in headache pain and improvement in BP among patients who present to an ED with migraine and elevated BP; (3) using the data from the migraine clinical trials, we also determined if an elevated baseline BP identifies a group of patients less likely to respond to standard migraine treatment.

We analyzed 2 distinct data sets. The first, NHAMCS, is a national probability sample of all US ED visits. The second is a compilation of data gathered during 3 ED-based migraine randomized controlled trials. We defined elevated BP as follows: moderate elevation—systolic BP (SBP) ≥150 mm Hg or diastolic BP (DBP) ≥95 mm Hg; marked elevation—SBP ≥165 mm Hg or DBP ≥100 mm Hg; and severe elevation—SBP ≥180 mm Hg or DBP ≥110 mm Hg. We report the association between headache and elevated BP in NHAMCS using odds ratios (ORs) with 95% confidence intervals (CI). We report the correlation coefficient and r² for the association between improvement in BP and improvement in headache pain in our clinical trials data set. Finally, using our clinical trials database, we determined the influence of elevated BP at baseline on response to migraine medication by constructing a linear regression model in which the dependent variable was improvement in 0 to 10 pain score between baseline and 1 hour, and the primary predictor variable was presence or absence of elevated BP at baseline.

Headache was the primary complaint in 3.7% (95% CI, 3.4-4.0%) of all US ED visits, corresponding to 4.8 million (95% CI, 4.2-5.4 million) patient visits. Among US ED patients, those with headache were more likely than patients with other chief complaints to have markedly (OR, 1.37; 95% CI, 1.16-1.61) or severely elevated BP (OR, 1.49; 95% CI, 1.17-1.90). In our clinical trials data set of patients with migraine with moderately elevated BP, there was no correlation between improvement in pain score and improvement in SBP (r = −0.07, r² = 0, P = .465) or DBP (r = −0.03, r² = 0, P = .75). Similarly, there was no correlation between improvement in headache and improvement in BP among patients with migraine with markedly elevated BP (for SBP, r = −0.19, r² = 0.04, P = .89; for DBP, r = −0.02, r² = 0, P = .87), nor among patients with severely elevated BP (for SBP, r = 0.06, r² = 0, P = .81; for DBP, r = 0.03, r² = 0, P = .90). Patients with moderately elevated BP had slightly less improvement in their 0 to 10 pain score than patients with BPs below this cutoff (−0.6; 95% CI, −1.2 to −0.1; P = .03). This was more pronounced among patients with markedly elevated BP (−0.9; 95% CI, −1.7 to −0.2).

Although there is an association between elevated BP and headache among patients presenting to an ED, improvement in headache is not associated with improvement in BP.