Chronic migraine: its epidemiology and impact

Chronic migraine (that is to say, cases where migraine is suffered on 15 or more days per month) is an illness that affects approximately 0.5-2.5% of the population, depending on the statistics that are analysed and the definition of chronic migraine used. The incidence of transformation from episodic to chronic migraine is 3% per year, and 6% go from low-frequency (1-9 days/month) to high-frequency migraine (10-14 days/month). The risk factors for developing chronic migraine are genetic, frequent use of painkillers, being female, having poor hygienic-dietary habits, developing anxiety/depression, having a low socioeconomic status, suffering from obesity and being divorced or widowed. Despite the modification of the risk factors, it has still not been proved that the chances of developing chronic migraine can be lowered. Chronic migraine has an important impact on patients' quality of life, as measured on disability, quality of life and impact on daily activities scales. These patients have twice the chance of suffering from depression, anxiety and chronic pain, which means they therefore need greater health care. Many have still to be diagnosed and treated, however. In a Spanish epidemiological study, a follow-up was carried out on patients with chronic daily headache after undergoing a therapeutic intervention and up to 60% of the patients showed improvement. In other words, with increased interest and diagnosis of this illness, many patients would benefit from suitable treatments.