How Do Hypertensive Disorders Impact Risk of Migraine-Associated Maternal Stroke?

Hypertensive disorders attribute for approximately 25% of excess cases of maternal stroke associated with migraine, according to research published in JAMA Neurology. Stratified analyses found preeclampsia appeared to contribute the most to excess risk associated with hypertensive disorders.

Although hypertensive disorders have been hypothesized to mediate the association between migraines and an increased risk of maternal stroke in the perinatal period, the relationship has not yet been formally quantified.

In a retrospective study, investigators assessed birth certificate and hospital discharge summary data from 3 million live, single births. All births took place in California between January 2007 and December 2012.

International Classification of Diseases, Ninth Revision (ICD-9) codes were used to identify migraines during pregnancy/delivery, ischemic and hemorrhagic stroke, and hypertensive disorders, including preeclampsia. Stroke codes were analyzed separately for occurrence during pregnancy/delivery or postpartum periods.

A multivariable log-linear regression, adjusted for age, body mass index, and other factors was used to estimate the association between migraine and stroke.

Of the 26,440 women migraineurs (914 per 100,000 deliveries), 843 women experienced strokes (29 per 100,000 deliveries), while ischemic strokes accounted for 58% of all stroke events.

The researchers found “women with migraines were more likely to be non-Hispanic white, have private insurance, have obesity, have diabetes (preexisting or gestational), have a mental health disorder, use tobacco, and use drugs or alcohol.”

Data also revealed that women with migraines, compared with women without migraine, during pregnancy were more likely to have:

• A hypertensive disorder: 15.1% vs 7.0% (adjusted risk ratio [aRR], 1.6; 95% CI, 1.6-1.7)
• A stroke during pregnancy or delivery: 0.15% vs 0.01% (aRR, 6.8; 95% CI, 4.7-9.8)
• A postpartum stroke: 0.05% vs 0.01% (aRR, 2.1; 95% CI, 1.2-3.7)

Effects were twice as strong for models of ischemic stroke compared with hemorrhagic stroke, according to the authors. A mediation analysis adjusted for potential confounders found “hypertensive disorders mediated 21% of the risk of stroke during pregnancy/delivery and 27% of the risk of postpartum stroke.”

Based on their findings, the authors hypothesize other pathways between migraine and stroke may exist during the perinatal period, including pathophysiologic changes like increased blood volume and cerebral circulation.

Because it is likely that only severe and active migraines are recorded in discharge summaries, the researchers note the stronger risk ratios reported may not be generalizable to less severe migraines. An additional limitation to the study was the lack of data recorded on migraine treatment.

“Although strokes are rare events, the associated morbidity and mortality warrants focus on identifying modifiable intervention targets,” they conclude.

Reference:

Bandoli G, Baer RJ, Gano D, Pawlowski LJ, Chambers C. Migraines during pregnancy and the risk of maternal stroke. JAMA Neurol. Published online June 1, 2020. doi:10.1001/jamaneurol.2020.1435