–But clinical implications are unclear since there’s no known mechanism
Women who have migraine headaches have a significantly increased risk of cardiovascular disease, according to new results from a large observational study published in the BMJ.
Earlier studies have established a strong link between migraine and stroke, which the the new study now extends to other types of cardiovascular disease. However, the clinical implications are uncertain since there is no definite mechanism to explain the association.
Researchers analyzed data from more than 115,000 women followed for more than 20 years in the Nurses’ Health Study II. More than 17,000 participants reported a migraine diagnosis. Women who had migraines were more likely to have other risk factors for cardiovascular disease, including hypertension, hypercholesterolemia, family history, obesity, and history of smoking.
After adjusting for the known risk factors, women with migraine had a significantly elevated risk for developing major cardiovascular disease (hazard ratio 1.50, CI 1.33 to 1.69). The greatest increase in risk was for stroke (HR 1.62) and for angina/coronary revascularizations (HR 1.73).
The findings were consistent and robust across multiple analyses. But the authors acknowledged that, as with any observational study, cause-and-effect could not be demonstrated and that residual confounding factors might offer “a potential alternative explanation.”
The chief weakness in the link between migraine and cardiovascular disease is the lack of “clear mechanisms… that could explain the increased risk of cardiovascular disease,” write the authors. There is also no evidence looking at “whether prevention of migraine attacks reduces these risks.”
In an accompanying editorial, Rebecca Burch, MD, of Harvard Medical School, and Melissa Rayhill, MD, of SUNY Buffalo, wrote that “it is time to add migraine to the list of early life medical conditions that are markers for later life cardiovascular risk.” But, they warned, “the magnitude of the risk should not be over-emphasized,” because the increased risk “is small at the level of the individual patient but still important at a population level because migraine is so prevalent.”
Burch and Rayhill also warned against any attempt to use the association to influence treatment. Without better evidence, they wrote, “migraine is probably best thought of as a situation in which the medical urge to ‘do something’ (beyond currently recommended assessments for cardiac risk and advocating a healthy lifestyle) should be resisted.”
Burch affirmed her position in an email interview. “There is currently no evidence to recommend any changes in how physicians manage cardiovascular risk in patients with a history of migraine. If a patient has a history of migraine, it might remind the physician of the importance of assessing cardiovascular risk in that patient. Once the risk has been assessed, however, management would be the same: treatment of hypertension and hyperlipidemia, recommending regular exercise, etc.”
The first author of the study, Tobias Kurth, MD, of the Harvard School of Public Health, agreed with the editorialists and said that that physicians “cannot really make any inference of treatment” based on the association in the study. “Physicians may want to discuss vascular risk with patients and reduce the risk by addressing known vascular risk factors (ie, where we know that intervention helps).”