A prevalence study of 9000 Swedish school children conducted in 1955 showed that nearly 4% had migraine. The prevalence of migraine was 1.4% at 7 years of age and 5.3% at 15 years of age. From the age of 11 there was a gradual increase of migraine headache and a predominance among girls. A subgroup of 73 children with pronounced migraine and an average onset of 6 years was followed during a period of 40 years. The results showed that 23% of the children were migraine-free before the age of 25, boys significantly more often than girls. However, around the age of 50, more than half of the migraine group still had migraine attacks. A recall bias was found in that a number of the subjects in their middle-life (41%) could not remember that they had had aura symptoms previously of those who had become parents, 52% have in their present or previous families had one child or more who had developed recurrent headache, probably of the migraine-type.
