Wednesday August 25 2010
Other risk factors such as diabetes and smoking all have much stronger effects
"People who suffer from a severe form of migraine are more likely to die of heart disease and strokes,” reported The Daily Telegraph. It said that people who had migraine with aura were 28% more likely to die from coronary heart disease and 40% more likely to die of stroke.
The Icelandic study asked people about their migraine history when they were middle aged and then followed them for up to 40 years. People who had migraine with auras (visual or sensory disturbances before their headache) were found to have a slightly higher risk of death from heart disease, stroke or non-cardiovascular diseases. The effect was not seen in people who had migraines without aura.
The researchers emphasise that this represents only a small increase in absolute risk. Other risk factors such as high blood pressure, diabetes, smoking and high cholesterol all have much stronger effects, and people should focus on reducing these. These findings highlight the need for further research into the causes of migraines with aura and if there is any association with the causes of cardiovascular disease.
Where did the story come from?
The study was carried out by researchers from the University of Iceland and was funded by the same university. The research was published in the (peer-reviewed) British Medical Journal.
This research was well reported by The Daily Telegraph and the Daily Mail. The Daily Express said that people who suffer from migraine are more likely to die from ‘heart attack, stroke or cancer’. The research looked at heart attack and stroke risks separately, but made no assessment of the risk of cancer associated with having migraine.
What kind of research was this?
This prospective cohort study investigated whether there was a link between having migraines in middle-age and the later risk of dying from cardiovascular disease (heart disease or stroke). The researchers say that many previous studies have indicated that migraine is a risk factor for cardiovascular disease.
However, it is less well understood how migraine affects the risk of dying from cardiovascular disease. To test this, the researchers looked at the risk of death from cardiovascular disease and death from all causes and whether there was an association with the person having migraine in middle age up to 40 years previously.
What did the research involve?
Participants were part of a cohort study called the Reykjavik Study, established in 1967 to prospectively study cardiovascular disease in Iceland. The study included men and women born between 1907 and 1935 and living in Reykjavik. There were 18,725 participants in the study with an average age of 52.8 years when they entered it.
The participants were asked about their experience of headaches. Those who had headaches once or more a month were asked whether the headaches were accompanied by any of the features of migraine, such as nausea or vomiting, headache affecting one side of the head, sensitivity to light, visual disturbances during or before the headache, or numbness on one side before the headache. The participants were grouped as:
- no headache (those having less than one headache a month)
- non-migraine headache
- migraine without aura
- migraine with aura, where an aura was visual or sensory disturbances before a headache
At the same time they were asked about their headache, participants were asked about their lifestyle and related heart disease risk. Physical measurements were taken, lung function assessed and an electrocardiogram was performed to assess heart functions. A blood sample was also taken.
The participants were followed for up to 40 years until 2007. The median (average) length of follow-up was 26 years. The cause of death for participants who died was recorded.
What were the basic results?
Out of 18,725 participants, 10,358 died in the 40-year follow-up. A total of 4,323 died from cardiovascular disease. Of these, 2,810 died from heart disease, 927 from stroke and 586 from other forms of cardiovascular disease.
Overall, 11% of the participants were classified as having migraine. Between sexes, 6% of male and 15% of female participants had migraine. There were some differences in the characteristics of the participants when they first started the study. For example, those who had migraine or headache were significantly younger than those without headache. Men with migraine had lower blood pressure than men without headache. Compared to those without headache the participants with migraine tended to have had less education and were more likely to be taking hormone treatment or medication to lower blood pressure.
The chance of death differed between people who did and did not have headaches. Those with migraine (with or without aura) had a 15% increased chance of death from any cause within the 40-year follow-up compared to people with no headache. They also had a 22% relative increased risk of dying from cardiovascular disease (hazard ratio [HR] 1.22, 95% confidence interval [CI] 1.10 to 1.36), compared to people with no headache.
Women, but not men, had a borderline increased risk of death from cardiovascular disease if they had non-migraine headache relative to those with no headache (HR 1.13, 95% CI 1.01 to 1.27). The increased risk of death for people with migraines was found only to apply to stroke or heart disease deaths and not to other cardiovascular disease related deaths.
When the researchers repeated a separate analysis for people who had migraines without auras and people who had migraines with auras, they found that the increased risk of death in the follow-up period from all cause, cardiovascular disease, non-cardiovascular disease, heart disease and stroke only applied to participants who had migraine with aura compared to headache-free individuals. (All cause mortality HR 1.21 95% CI 1.12 to 1.30; cardiovascular disease HR 1.27, 1.13 to 1.43; non-cardiovascular disease HR 1.15, 95% CI 1.04 to 1.27; heart disease HR 1.28, 95% CI 1.11 to 1.49; and stroke HR 1.40, 95% CI 1.10 to 1.78).
The researchers found that at the age of 50, men were more likely to die within the next 10 years than women. The absolute risks for men were 6.8% for those with no headache and 8.0% for those who had migraine with aura. The absolute risks for women were 3% for those with no headache and 3.6% for those who had migraine with aura. The risk of dying within 10 years after the age of 70 was 40.6% in men without headache compared to 46.1% in men who had migraine with aura. In women, the risk of death was 24.1% for headache-free individuals and 27.9% for women with migraine with aura.
How did the researchers interpret the results?
The researchers said that 'migraine with aura is an independent risk factor for [death from cardiovascular disease] and all cause mortality in men and women', but it is still weaker than major established risk factors such as smoking, diabetes and high blood pressure.
They add that people with migraine without aura are not at increased risk.
This is a large, cohort study with a lengthy follow-up. There are several limitations that should be taken into account when interpreting this research.
- Only people who reported more than one headache a month were asked about their migraine features. Therefore, the people with migraines included in this study may only have been those experiencing high frequency migraine attacks.
- The proportion of migraine sufferers who experienced aura is higher than reported in other population studies. The researchers say that this may be due to non-aura-specific visual symptoms such as vision blurring being classified as an aura. They also say the combination of visual symptoms and headache can be symptoms of transient ischemic attack or mini stroke (a short lasting change in blood flow to a particular area of the brain). If these were misclassified as migraine with aura then this could lead to an increased association between migraine and aura and cardiovascular disease being observed.
- The researchers collected data on risk factors for cardiovascular disease only at the start of the study. The lifestyle of the participants may have changed over the long course of the follow up, giving them an increased or decreased risk.
- The researchers did not collect information on medications that the people with migraines may have been taking, which could have included migraine-specific medication such as triptans.
- Although the study population was large, the Icelandic population may not reflect the demographics of the UK population. As such, these results may not be directly relevant to the UK population.
This study found that people with migraine with aura are at modestly increased risk of death in later life compared to people who are headache-free, independent of classic risk factors for cardiovascular disease.
However, the researchers emphasise that the absolute risk increase is low and the increased risks were relatively small. The focus should be on changeable risk factors such as high blood pressure, smoking and cholesterol for reducing the risk of cardiovascular disease regardless of migraine status.