About 13% of all women suffer migraine attacks, while only about 6% of men do.

The difference is almost entirely because many women get migraine attacks around the time of menstruation.

What do the statistics say?

In 1970, a Swedish survey of 1676 women who took contraceptive pills and who hadn't formerly had migraine showed that about 10% of the women complained of migraine, mostly during the "pill-free" week. Other women get less migraine when they take contraceptive pills. The same general conclusions about contraceptive pills that contain oestrogen appear again and again in the medical literature.

What does chemistry say?

Just before menstruation, blood contains more of the female hormone oestrogen than at other times in the monthly cycle. When menstruation starts, the amount of oestrogen in the blood falls. It has therefore been a common assumption that there is a connection between the amount of oestrogen in the blood and migraine. Various scientists have proposed that, for example, it could be the fall in the amount of oestrogen in the blood at the start of menstruation that triggers migraine.

Studies of female migraineurs have also shown that migraineurs who always have migraine with aura have a higher amount of the hormone estradiol (a hormone in the oestrogen group), while migraineurs without aura have estradiol amounts more like those of non-migraineurs. A study published in the scientific journal "Headache" in June 1996 showed that it is only women whose blood-oestrogen is higher than normal that get migraine, while women with normal blood-oestrogen levels don't get migraine at menstruation.

At the same time as blood-oestrogen levels are rising towards menstruation, the amount of the chemical mono-amino-oxidase [1] is falling in the blood platelets [2]. A group of Italian scientists wrote in the scientific journal "Cephalagia" in 1996 that because female migraineurs have less mono-amino-oxidase in their blood platelets than other women at the start of menstruation, this makes them more susceptible to migraine than other women.

How do hormones affect the body?

One study looked at how the muscles in the jaw reacted when oestrogen levels in the blood were high. They found that the jaw-muscles reacted more strongly during the first day of the monthly cycle than in the middle of the cycle - in other words, women clench their teeth more strongly the first day they menstruate. The researches also found that the time between a muscle contracting, until it can contract again, varies depending on the proportion in the blood of estradiol to progesterone (another hormone whose blood-content changes during the menstruation cycle).

Scientists theorize that when blood-oestrogen levels are high, the sudden fall in blood-oestrogen levels at the start of menstruation causes reduced activity in the nerves leading to synapses [3]. When reduced signals come to a synapse, the receiving nerve compensates by amplifying those signals it does get. When a woman menstruates and oestrogen levels have fallen, the sending nerves once again signal with normal strength, the receiving nerves react too strongly until they again have "adjusted" to the new signal level. The "overreacting" nerves can be both those that lead to the jaw muscles and those that cause the blood-vessels to contract. The increased risk of getting migraine comes from the overreaction of the nerves leading to the blood-vessels. The overreaction of the nerves leading to the jaw muscles causes women to clench their teeth without realizing it, and this can also lead to tension headaches.

What about older women?

Today we are very conscious about how important it is to avoid decalcification of the bones. Many women take oestrogen after the menopause to avoid decalcification later in life. A study was carried out that included 16 women who earlier had had menstruation migraine, and who took extra oestrogen in the form of a monthly injection of estradiol. All of the women got migraine about 18 days after their injection, i.e. when the amount of hormone in their blood fell. Women without a history of migraine got no migraine attacks from the same treatment.

Even though it formerly was true that you could count on avoiding migraine after the menopause, it's only partly true today, because of the number of women who choose to take supplementary hormones.

What about pregnancy?

There are many reports that migraine attacks disappear during pregnancy, but there are also accounts of the opposite. One study showed that migraine can come especially during the last months of a pregnancy.

Can anything be done about the problem?

There are reports that oestrogen plasters applied in the period around menstruation can ease migraine attacks, because the fall in blood-oestrogen levels is minimized by an extra supply of hormones. Careful consideration should also be given as to whether supplementary hormones are needed after the menopause.

There is one further group who apparently cannot for the moment find alternatives to treatment with oestrogen, those women who have had their uterus and/or ovaries removed, and who need supplementary hormones to be able to live a normal life.

60% of all female migraineurs think that their migraine is connected with menstruation, and ca. 15% of all female migraineurs get migraine attacks exclusively in connection with menstruation. Menstruation-migraine is just as unpleasant as any other form of migraine and cannot therefore be dismissed as 'women’s babble'.

The only 'advantage' with menstruation-migraine is that it is fairly easy to forecast.

It is unreasonable that women who have menstruation-migraine have to accept that it is just something you have to live with, if preventive treatment exists.

It is unreasonable that you have to accept migraine as a side-effect if you don’t want children or don’t want osteoporosis in old age.

It is therefore important to go to your doctor and have an in-depth discussion about the problem if you have the least grounds to think that your migraine has started after you began any form of treatment involving taking hormones.

[1] Monoaminoxidase is an enzyme which breaks down various chemicals called monoamines. Some monoamines can trigger migraine by disturbing the signals from nerves so that the blood-vessels in the brain contract.

[2] Blood platelets transport chemicals round the body so they get to where they’re needed.

[3] A synapse is the junction where one nerve sends a message to the next nerve in sequence. Messages from nerve to nerve are sent as chemicals which are released from the sending nerve and taken up by the receiving nerve.