April 28, 2017
The association between migraine and hypertension has mostly been explored in cross-sectional and case-controlled studies, and the evidence from this research has been mixed, the authors say.
It's not clear from these studies whether migraine increases the risk for hypertension or hypertension increases the risk for migraine, said lead author, Pamela Rist, ScD, Brigham and Women's Hospital, Boston, Massachusetts.
Dr Rist presented results of the new analysis here at the American Academy of Neurology 2017 Annual Meeting (AAN).
The current study population was included in the Women's Health Study, which started as a randomized double-blind, placebo-controlled trial on the effects of low-dose aspirin and vitamin E on the primary prevention of cardiovascular disease and cancer.
In the early 1990s, the study enrolled almost 40,000 US female health professionals aged 45 years and older without a history of cardiovascular disease, cancer, or other major illnesses.
The trial itself ended in March 2004, but observational follow-up is ongoing. The data presented are current to the end of 2015, said Dr Rist.
At the start of the study, participants were asked whether they had experienced migraine headaches. If they had had such headaches in the past year, they were asked about attack frequency and characteristics of attacks, including presence of aura.
On the basis of responses, researchers divided the women into four categories: (1) no history of migraine, (2) active migraine with aura, (3) active migraine without aura, and (4) past history of migraine.
Incident hypertension was defined as a new physician diagnosis or a new self-reported systolic blood pressure of 140 mmHg or greater or a diastolic blood pressure of 90 mmHg or greater.
Because antihypertensive medications are used to treat migraines, women were censored when they reported initiation of such medications and were not considered to be incident cases. Researchers also excluded women with a history of hypertension at baseline and those with missing information on migraine status.
The women were followed for a mean of 12.2 years.
At baseline, the normotensive population included 29,040 women with data on migraine status. Of these, 23,819 women reported no history of migraine, 1516 reported active migraine with aura, 2292 reported active migraine without aura, and 1411 women reported a past history of migraine.
The researchers identified 15,176 incident hypertension cases.
Compared with women with no migraine, those who had active migraine, with or without aura, tended to be slightly younger and were more likely to have a history of high cholesterol, to be never smokers, and to have rarely or never consumed alcohol.
The researchers first adjusted for age and then ran multivariable-adjusted models also adjusting for randomized treatment assignment (aspirin or vitamin E) and a variety of other potential confounders, including body mass index, smoking, and use of hormone replacement therapy or cholesterol-lowering therapy.
Compared with women without a history of migraine, those who experienced migraine with aura had about a 9% increased risk for hypertension (RR, 1.09; 95% confidence interval [CI], 1.02 - 1.18; multivariable adjusted model) while those who experienced migraine without aura had about a 21% increased risk (RR, 1.21; 95% CI, 1.14 - 1.28).
Those with a past history of migraine had about a 15% increased risk for hypertension (RR, 1.15; 95% CI, 1.07 - 1.23).
A sensitivity analysis that included new reports of antihypertensive medication use in the outcome definition showed very similar results to the main analysis, said Dr Rist.
Another secondary analysis investigated whether women with active migraine experiencing an increase in migraine frequency had an increased risk for hypertension. "We did not see a clear pattern," said Dr Rist.
Strengths of this study were that it was prospective, had a longitudinal design, and included information on migraine subtypes. A limitation was that migraine status and incident hypertension were self-reported, introducing the potential for misclassification.
"We are also concerned about generalizability," said Dr Rist. "Our cohort is entirely female, and mostly white women. I don't know if the results will generalize to other populations."
In response to a query from delegate about family history of, or genetic risks for, migraine, Dr Rist said the researchers did not have this information. "We just have family history of myocardial infarction," although gathering data on genetics "is a great idea."
In response to another question, Dr Rist said the researchers did not have information on age of migraine onset, which is "another limitation of this cohort."
The Women's Health Study is supported by grants from the National Institutes of Health. Dr Rist has disclosed no relevant financial relationships.