Untangling stroke and migraine
By: David Kernick, GP with a special interest in headache, Exeter Headache Clinic
People with migraine often worry about whether they will get a stroke and want to know what they can do to prevent one. In this article, I try to unpack this complex picture so people better understand the link between migraine and stroke. I also give out a few tips for what you should do if you’re worried or want to minimise your risk.
What is a stroke?
A stroke occurs when the brain gets damaged due to a problem with its blood supply. This occurs for three reasons:
- Blockage to an artery – what is called an ‘ischaemic stroke’. This is the most common type of stroke.
- Bleeding due to a ruptured artery – a ‘haemorrhagic stroke’
- A temporary blockage from a small clot that originates in an artery outside the brain and is transported to it in the blood stream – a ‘transient ischaemic attack’ (TIA). This doesn’t cause irreversible damage.
Is there an increased risk of stroke and migraine?
The simple answer is yes, but this increased risk is small and predominately for people with migraine with aura. Most of this slightly increased risk occurs in women under the age of 45. In this group, seven out of 100,000 women with migraine with aura will have a stroke over a one year period, approximately twice the number of people who don’t have migraine with aura.
This is still a small risk and is approximately the same number of deaths that will occur on the road in the UK per year. This risk is mainly for ischaemic stroke, from which 25% of people can be expected to make a full recovery.
What causes this increased risk?
We don’t actually know. A number of theories have been put forward, including abnormalities in the blood vessel walls or in the clotting components of the blood.
Are there any other factors that increase this risk?
Yes, smoking and taking a contraceptive that contains oestrogen significantly increase this risk. Raised blood pressure, glucose levels, cholesterol, and obesity are also important but less so. There is no increased risk from the small amount of oestrogen in HRT preparations and there is no increased risk from the progesterone only pill or implant.
Confusing aura with stroke
Aura can occur without headache and this is often confused with a transient ischaemic attack or, if the aura is more prolonged, an ischaemic or haemorrhagic stroke. A useful pointer is that an aura evolves gradually whereas a TIA is of sudden onset. This is because an aura is a wave of electricity that spreads across the surface of the brain whereas a TIA reflects a sudden blockage. Aura without headache is quite common, but it’s worth getting it checked out by your GP, particularly if you don’t experience migraine headache with aura at other times.
What should I do to reduce my risk of stroke?
Avoiding oestrogen containing contraception and not smoking are the most important things you can do to reduce your risk. It is also important to maintain overall good vascular health with a well-balanced diet, exercise, and avoidance of obesity together with appropriate management of blood pressure and blood glucose.
Reduction of elevated cholesterol can be important and your GP will assess a range of factors in deciding whether or not to treat you with a statin, a powerful group of drugs that reduce cholesterol and helps to prevent blood vessel damage. As with all drugs it is important to weigh up the advantages and disadvantages of using statins but treatment is recommended if you have a risk of a vascular problem of 10% or more over the next 10 years. There is a tool available online that GPs use to help assess this risk, looking at all of the important risk factors. If you have migraine with aura then the final score should be multiplied by two but in practice, if you are a young female the level of risk that triggers treatment will rarely be reached.
Ongoing research will improve our understanding of the relationship between migraine and stroke and offer new ways of preventing it. There is currently no evidence to suggest that reducing the frequency of attacks will reduce the risk of stroke.
It’s far more important to reduce the factors known to increase risk, particularly smoking and high cholesterol, and to maintain overall good vascular health.