"Women who suffer migraines have a 50 per cent greater chance of developing a major heart … problem," the Daily Mail reports.
Individual risks to women remain small, but because migraines are so widespread, this could be an issue of concern at a public health level.
Doctors already knew migraine is linked to stroke, as we discussed back in 2009, especially migraine with aura.
This is when a migraine is preceded by warning signs and symptoms, such as visual problems or feeling dizzy. We don't know whether migraine is a direct cause of these problems.
Although a 50% increased risk sounds like a lot, you have to take into account the baseline (absolute) risk.
Only 1.2% of all the women in the study had a major cardiovascular disease event like a heart attack or stroke, so increasing that by 50% takes the risk to 1.8%, or around a 1 in 50 chance.
The authors are calling for research to find out more about whether treatment that reduces the incidence of migraines can also reduce the risk of heart attacks and strokes.
A related editorial makes the point that we also have to be sure that preventative treatments for heart disease, such as statins, don't actually make the problem worse for women with migraines.
Where did the story come from?
The study was carried out by researchers from Charité-Universitätsmedizin in Germany, Harvard Medical School, the Harvard TH Chan School of Public Health, and the Washington University School of Medicine in the US.
It was funded by the US National Institutes of Health.
There is also a related editorial written by independent experts, who provide an interesting insight into the study's implications.
The UK media's coverage was accurate, with many sources stressing that the risk to individual women was small.
But this tone of reassurance was ignored by many of the headline writers – for example, the Daily Express' headline, "Suffer with migraines? Female sufferers 'more likely' to DIE from heart disease and stroke".
Many of the headlines were unnecessarily alarming, not least because stress and anxiety are known triggers for migraines.
The Daily Telegraph said the study suggested that statins might reduce risk for people with migraines, which is misleading, as the potential role of statins was not investigated in this study.
What kind of research was this?
Prospective cohort studies, especially of this size and length, can be useful ways to identify links and trends in health.
However, observational studies like this one cannot prove that one factor – in this case, migraine – causes another (heart attack or stroke).
What did the research involve?
Researchers used data from a big ongoing study of women's health in the US, which began in 1989.
Women aged 25 to 42 at baseline were asked a wide range of questions about their health and lifestyle, and were followed up every two years until June 2011.
After adjusting their figures to take account of confounding factors, researchers looked to see whether women who said they had been diagnosed with migraine were more likely to have had or died from cardiovascular disease, including heart attack and stroke.
Women were asked about migraine at the start of the study and twice in follow-up questionnaires.
They were asked about cardiovascular disease every two years. Women with cardiovascular disease in 1989 were not included in this study.
The wide range of confounding factors the researchers took into account included:
- high cholesterol
- high blood pressure
- whether a woman had gone through the menopause
- family history of heart attack
- use of widely used medications, such as hormone replacement therapy (HRT), oral contraceptive pills, paracetamol, aspirin, and non-steroidal anti-inflammatory drugs (NSAIDs)
The researchers used these factors to construct models to test their results and take account of known risks for heart disease and stroke.
What were the basic results?
Of the 115,541 women in the study, over the course of 22 years follow-up:
- 17,531 (15%) had migraine
- 1,329 (1.2%) had a heart attack, stroke, angina, or needed a procedure to reopen the blood vessels
- 223 (0.2%) died of cardiovascular disease
After adjusting for confounding factors, the chances of getting major cardiovascular disease were 50% higher for women with migraine than women without (adjusted hazard ratio 1.5, 95% confidence interval 1.33 to 1.69). The link was stronger for stroke than heart attack.
Women who had migraine were more likely to be overweight, smoke, and have high blood pressure and cholesterol.
However, these factors did not explain the raised risk of heart attack and stroke, as the researchers had already adjusted their figures to account for them.
How did the researchers interpret the results?
The researchers said they found "consistent associations" between migraine and cardiovascular disease, which "persisted" after adjustment for traditional cardiovascular risk factors.
They said there is now an "urgent need" to understand what's behind the link, so they can look at treatments to prevent heart attacks and strokes in women with migraine.
The researchers also suggested that people with migraine should have their overall cardiovascular risk assessed, so they can be advised about any steps they can take to reduce it – for example, reducing blood pressure if it's too high, or stopping smoking if they smoke.
This study shows a strong link between migraine and cardiovascular disease, extending the link already found between migraine and stroke. However, many questions remain.
We don't know if the results are relevant to men who have migraines, as all the people in the study were women. We also don't know if the results apply to non-white populations, as most of the women in the study were white.
Previous studies on stroke have shown that the group at highest risk is who get an "aura" before a migraine – sensation(s) that tells them the migraine is on its way.
But this study did not ask people about aura, so we don't know whether it's only people with aura who are at risk of heart disease.
We don't know what causes the increased risk of cardiovascular disease for people with migraine.
Although the researchers took into account a wide range of confounding factors, it's possible that some unaccounted factors were responsible for the link.
Alternatively, a third underlying factor might cause both cardiovascular problems and migraine.
Until we fully understand what's behind the link, it's too early to know whether treatments for migraine – or any other treatments – will help reduce the risk, or could possibly make it worse.
As the editorial in the BMJ points out, aspirin – often used to prevent cardiovascular disease because of its blood-thinning properties – was found to actually increase the risk of heart attacks in women who had migraines with aura.
Regular exercise is also known to help reduce stress levels and boost mood, which could also help to reduce the number of migraines you experience.