Epidemiology of cluster headache.

Cluster headache is rare, occurring in less than 1% of the population. Studies suggest that, in addition to the pain and associated autonomic disturbances recognized to be characteristic of the syndrome, patients also may experience nausea, photophobia, behavioral agitation, or restlessness. A decreasing male:female ratio also has been noted, perhaps attributable to lifestyle trends adopted by more women that were previously associated with men, such as tobacco use, alcohol consumption, and working outside of the home. The relationship between cluster headache and hormonal events does not appear to be strong. Hormonal influences on the chronic form of cluster headache in women are a subject of investigation. The emerging understanding of the genetics of cluster headache increasingly suggests a genetic component, with familial transmission now recognized to be more common than previously appreciated. Head trauma, coronary artery disease, and migraine appear to be present in more patients with cluster headache than can be explained by chance alone. Ethnic and racial differences in prevalence are less well understood.