Epidemiology and comorbidity of headache.

The burden associated with headache is a major public health problem, the true magnitude of which has not been fully acknowledged until now. Globally, the percentage of the adult population with an active headache disorder is 47% for headache in general, 10% for migraine, 38% for tension-type headache, and 3% for chronic headache that lasts for more than 15 days per month. The large costs of headache to society, which are mostly indirect through loss of work time, have been reported. On the individual level, headaches cause disability, suffering, and loss of quality of life that is on a par with other chronic disorders. Most of the burden of headache is carried by a minority who have substantial and complicating comorbidities. Renewed recognition of the burden of headache and increased scientific interest have led to a better understanding of the risk factors and greater insight into the pathogenic mechanisms, which might lead to improved prevention strategies and the early identification of patients who are at risk.