Migraine/stroke link more complex than originally thought

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Initial results from the Atherosclerosis Risk in Communities (ARIC) study found that migraine with aura (MA) was associated with higher risk of ischemic stroke. However, data from a post-hoc analysis appearing in Headache suggest that the linkage may not be as straightforward as originally thought.

In the original study, participants were interviewed at their third in-person visit (1993-1995) to gather migraine history and were subsequently followed for ischemic stroke incidence for 20 years. For the post-hoc analysis, the authors looked at risk of ischemic stroke and age of migraine onset. 

Questionnaires were administered to all 11,592 participants to gather headache information and classify participants according to their reported headache types, either MA or migraine without aura (MO). In addition to headache data, the researchers also identified all stroke hospitalizations and deaths from 1987 to 2012 that occurred in the ARIC participants. 

Mean age of the study population was 61 years, 76.5% (8,872/11,592) were white, and 55.3% (6417/11,592) were female.  Migraines were more prevalent in women than in men (approximately 3:1) in each subgroup. Of the study participants, 13.9% (1613/11592) reported a history of migraines: 3.85% (447/11,592) with, and 9.7% (1,128/11,592) without, aura. Mean age of the participants when they first experienced migraine symptoms was 37 years. 

Between their third in-person visit and 2012, 5.95% (691/11,592) of the participants from the ARIC study overall had an ischemic stroke, compared with 5.26% (861/1,575) of participants from the study who reported migraines. In the patients with MA, stroke incidence was 6.67/1000 per year when age at headache onset was ≥ 50 versus 3.04 when age at onset was < 50.  MA onset at age ≥ 50 was significantly associated with ischemic stroke whereas MA onset at < 50 was not. No link was found between MO and ischemic stroke regardless of age of onset of headaches. 

The authors believe the findings from the post-hoc analysis can serve to better inform physicians about migraine patients’ risk of stroke. The initial findings from the ARIC study suggested that MA increased with ischemic stroke risk, whereas the post-hoc results indicate that MA is associated with stroke risk only in patients whose MA headaches began after age 50. 

The researchers also noted some limitations to their study. Migraine classification in ARIC was based on questionnaires administered later in life, which could result in recall bias. Furthermore, MA symptoms only included visual aura and may have inadvertently excluded migraine with sensory, motor, or brainstem aura due to the design of the questionnaires. Also, no data were available on frequency of participants’ migraines on an annual basis.