[Current status of migraine chronification in Japan]

Chronification of migraine headache is one of the major issues to resolve urgently. The prevalence of chronic migraine is close to 2％, and the chronification occurs in approximately 2.5％ of episodic cases annually.The pathophysiology of transformation from episodic to chronic migraine is still unclear. It is considered that there are several risk factors for migraine chronification; 1) non-modifiable: age, low education/socioeconomic status, and head injury, 2) modifiable: attack frequency, obesity, medication overuse, stressful life events, caffeine overuse, snoring, and other pain syndrome, 3) currently putative: allodynia, proinflammatory states, prothrombotic states, and specific genes.There were a few clinical reports concerning to the migraine transformation from abroad, but few data from Japan. The prevalence of chronic daily headache in our headache clinic in Japan was 20-30％. The medication overuse headache was the most prevalent form in the highest attack frequency (>15 days/month) grope. Discontinuation of overused medication and administration of prophylactic medication were effective, and 40％ of followed cases kept out of MOH at two years later.