A systematic review and meta-analysis «Etminan M, Takkouche B, Isorna FC, Samii A. Risk o...»1 included 14 studies (11 case-control studies and 3 cohort studies). The risk of stroke was increased in people with migraine (relative risk 2.16, 95% confidence interval 1.89 to 2.48). This increase was consistent in people who had migraine with aura (RR 2.27, 95% CI 1.61 to 3.19) and migraine without aura (RR 1.83, 95% CI 1.06 to 3.15), as well as in those taking combined oral contraceptives (COC) (RR 8.72, 95% CI 5.05 to 15.05).
In another meta-analysis «Schürks M, Rist PM, Bigal ME et al. Migraine and c...»2 (25 trials) migraine as a risk factor of stroke was assessed. Risk ratio was increased for migraine with aura, RR 2.16, 95% CI 1.53 to 3.03, but was not increased for patients without aura. Females were found to be at higher risk (RR 2.08; 95% CI 1.13 to 3.84), risk was increased with oral contraceptives (RR 7.02; 95% CI 1.51 to 32.68), and in particular, if associated to the smoking habit (RR 9.03; 95% CI 4.22 to 19.34).
A third meta-analysis «Spector JT, Kahn SR, Jones MR et al. Migraine head...»3 included 21 studies (13 case–control studies and 8 cohort studies) with a total of 622 381 patients. Compared with non-migraineurs, the odds ratio of stroke for migraine with aura was 2.25 (95% CI 1.53 to 3.33), in migraine without aura there was a nonsignificant trend only (OR 1.24, 95% CI 0.86 to 2.43). OR for the female gender was 2.43 (CI 95% 1.80 to 3.27).
A case-control study «...»4 based on nationwide database assessed the risk of stroke associated with migraine and combined hormonal contraceptives. Years 2006 to 2012, there were 25 887 ischemic strokes among females ages 15-49 years. Compared to those with neither migraine nor combined hormonal contraceptive use, OR for ischemic stroke among those with migraine with aura using COC was 6.1 (95% CI 3.1 to 12.1); migraine with aura without COC 2.7 (95% CI 1.9 to 3.7), However, in migraine without aura the use of COC did not increase the risk (migraine without aura with COC RR 1.8, 95% CI 1.1 to 2.9, and migraine without aura without COC RR 2.2, 95% CI 1.9 to 2.7). The joint effect of combined hormonal contraceptives and migraine with aura was associated with a 6-fold increased risk of ischemic stroke compared with neither risk factor.
A consensus statement «...»5 evaluated absolute risk of ischemic stroke in women aged 20 to 44 years in relation to the use of hormonal contraception and migraine status, see table «Absolute risk of stroke...»1.
| No migraine | Migraine with aura | |
| Without hormonal contraception | 2.5/100 000 | 5.9/100 000 |
| With hormonal contraception | 6.3/100 000 | 36.9/100 000 |
Comment: The quality of evidence is upgraded by large magnitude of effect.