Migraine without aura does not appear to be a factor. The relationship with heart problems is inconclusive with a single study supporting an association. Migraine does not appear to increase the risk of death from stroke or heart disease. Preventative therapy of migraines in those with migraine with aura may prevent associated strokes. People with migraine, particularly women, may develop higher than average numbers of white matter brain lesions of unclear significance. Epidemiology
Worldwide, migraine affects nearly 15% or approximately one billion people. It is more common in women at 19% than men at 11%. In the United States, about 6% of men and 18% of women experience a migraine attack in a given year, with a lifetime risk of about 18% and 43% respectively. In Europe, migraines affect 12–28% of people at some point in their lives with about 6–15% of adult men and 14–35% of adult women getting at least one yearly. Rates of migraine are slightly lower in Asia and Africa than in Western countries. Chronic migraine occurs in approximately 1.4 to 2.2% of the population.These figures vary substantially with age: onset of migraine is most commonly between 15 and 24 years of age, and occur most frequently in those 35 to 45 years of age. In children, about 1.7% of 7 year olds and 3.9% of those between 7 and 15 experience migraine, with the condition being slightly more common in boys before puberty. Children as young as two years may be affected.
There are a number of explanations for its occurrence, including activation of NMDA receptors leading to calcium entering the cell. After the burst of activity, the blood flow to the cerebral cortex in the area affected is decreased for two to six hours. It is believed that when depolarization travels down the underside of the brain, nerves that sense pain in the head and neck are triggered. Pain
The exact mechanism of the head pain which occurs during a migraine episode is unknown. Some evidence supports a primary role for central nervous system structures (such as the brainstem and diencephalon), while other data support the role of peripheral activation (such as via the sensory nerves that surround blood vessels of the head and neck). The potential candidate vessels include dural arteries, pial arteries and extracranial arteries such as those of the scalp. The role of vasodilatation of the extracranial arteries, in particular, is believed to be significant. Neuromodulators
Adenosine, a neuromodulator, may be involved. Released after the progressive cleavage of adenosine triphosphate (ATP), adenosine acts on adenosine receptors to put the body and brain in a low activity state by dilating blood vessels and slowing the heart rate, such as before and during the early stages of sleep. Adenosine levels have been found to be high during migraine attacks. Caffeines role as an inhibitor of adenosine may explain its effect in reducing migraine.