A new US study suggests that women who have migraines with aura (seeing spots and flashing lights), particularly those who smoke or use oral contraceptives, are at increased risk of having a stroke compared with women who do not have migraines.
The study is published in Stroke, a journal of the American Heart Association, and was carried out by researchers from the University of Maryland School of Medicine, Baltimore, Maryland, the VA Maryland Health Care System, also in Baltimore, and the US Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia.
According to the World Health Organization (WHO), migraine is a “primary headache disorder”, and most likely has hereditary factors. It happens when chemicals are released deep inside the brain that cause painful inflammations of the nerves and blood vessels in the head. Nobody knows what starts the process off and what decides how long a migraine episode lasts. The attacks appear and end spontaneously: for some people this is about once a year and for others it could be once a week.
As well as the painful headache, nausea is also a common symptom of migraine in adults, as is sensitivity to lights and sounds and occasionally vomiting. In children the most common symptom is abdominal pain.
Migraines usually start in puberty and mostly affect people between 35 and 45 years of age. Studies carried out in Europe and America show that up to 8 per cent of men and 18 per cent of women have a migraine each year. The prevalence in South and Central America is said to be similar, but lower in Asia, according to the WHO.
According to the British Association for the Study of Headache (BASH), around one third of migraine sufferers also experience migraine with “aura”, where they see flashing lights, spots or lines either just before or during the migraine episode.
The authors of the present study said that previous research has already linked migraine with aura with ischemic stroke, but few of them have looked into the clinical and physiological features of the link.
Dr Steven J. Kittner of of the University of Maryland School of Medicine and colleagues assessed the link between probable migraine with visual aura and probable migraine without visual aura (PMVA) with ischemic stroke among groups of women according to various factors including headache characteristics and various clinical features.
The case controlled study enrolled 386 women aged between 15 and 49 who had suffered a stroke for the first time, and matched them to 614 controls by age and ethnic status. The women completed questionnaires about their headache symptoms and were put in three groups: no migraine, probable migraine without visual aura, and probable migraine with visual aura (PMVA).
The results showed that:
* Women with PMVA had a 50 per cent greater risk of ischemic stroke compared to the no migraine group.
The risk was highest among those with no history of high blood pressure (hypertension), diabetes or heart attack (myocardial infarction).
* Women with PMVA who smoked and used oral contraceptives had a 7-fold increase in ischemic stroke risk compared to women with PMVA who did not smoke or use oral contraceptives.
* Also, women who had their first PMVA attack in the preceding year had a 6.9 fold increase in ischemic stroke risk compared to women with no history of migraine.
* Kittner and colleagues concluded that:
“PMVA was associated with an increased risk of stroke, particularly among women without other medical conditions associated with stroke. Behavioral risk factors, specifically smoking and oral contraceptive use, markedly increased the risk of PMVA, as did recent onset of PMVA.”
“Probable Migraine With Visual Aura and Risk of Ischemic Stroke. The Stroke Prevention in Young Women Study.”
Leah R. MacClellan, Wayne Giles, John Cole, Marcella Wozniak, Barney Stern, Braxton D. Mitchell, and Steven J. Kittner.
Stroke, Published online before print, Aug 9, 2007.