Differences Between Chronic and Episodic Migraine Go Well Beyond Frequency

Caroline Cassels

February 18, 2010

February 18, 2010 — Individuals with chronic migraine (CM) tend to be in poorer general health, less well off, and more depressed than those with episodic migraine (EM), new research suggests.

A large survey study reveals that compared with individuals with EM, those with CM are twice as likely to have depression, anxiety, and chronic pain.

In addition, the findings suggest that CM patients are significantly more likely to report respiratory disorders, including asthma, bronchitis, and chronic obstructive pulmonary disease, and cardiac risk factors, including hypertension, diabetes mellitus, high cholesterol levels, and obesity.

"Differences in the profiles between the 2 groups suggest that CM and EM diverge not just in the degree of headache frequency but in these other important areas. These differences might reflect differences in biological risk factors and provide valuable clues to further explore the differences between EM and CM", the study authors write.

Led by Dawn C. Buse, PhD, Montefiore Headache Center, Bronx, New York, the study is published in the February 18 issue of the Journal of Neurology Neurosurgery and Psychiatry.

Population-based studies show that CM has an estimated prevalence of 1.3% to 2.4%. However, the researchers note that it is the most common disorder in headache specialty practices.

Previous research also shows that compared with EM, CM is associated with greater migraine-related disability and impairment in headache-related quality of life as evidenced by high levels of sick leave, reduced productivity, and poorer quality of family life than their counterparts with EM. It also suggests that few receive an accurate diagnosis, and only 1 in 3 receive appropriate treatment.

According to the study authors, comorbidities of EM have been well characterized. However, they note, comorbidities of CM have rarely been studied in population-based samples.

To characterize and compare the sociodemographic profiles and the frequency of common comorbidities for adults with CM vs EM, investigators conducted a cross-sectional analysis of 2005 data from the American Migraine Prevalence and Prevention (AMPP) study, a longitudinal, population-based survey.

To be classified as having CM, respondents had to meet the second edition of the International Classification of Headache Disorders (ICHD-2) criteria for migraine headache and report an average of 15 or more headache-days per month within the past 3 months. Respondents with EM met ICHD-2 criteria for migraine and had 14 or fewer headache-days per month within the past 3 months.

A total of 11,904 respondents — 655 with CM and 11,249 with EM — were included in the final analysis. The investigators report that compared with EM, those with CM reported significantly lower household income. In addition, the study authors report that those with CM were significantly less likely to have full-time employment and nearly twice as likely to be occupationally disabled.

Furthermore, those with CM were approximately twice as likely to have depression, anxiety, and chronic pain and higher rates of respiratory and cardiovascular risk factors. In addition, those with CM were approximately 40% more likely to have heart disease and angina and 70% more likely to have had a stroke.

"These findings highlight the importance for clinicians to maintain diagnostic vigilance and provide appropriate treatment or referrals when necessary. When comorbid psychiatric disorders are present with CM, it is important to take both disorders into account in formulating a treatment plan and remain mindful of the negative impact that psychiatric disorders can place on treatment outcomes, adherences, and general quality of life," the study authors write.

The AMPP is funded through a grant to the National Headache Foundation from Ortho-McNeil Pharmaceuticals. Additional funding for the study was provided by Allergan Pharmaceuticals. Study investigators Aubrey Manack and Catherine Turkel are full-time employees of Allergan Pharmaceuticals in Irvine, California. The study authors have disclosed no relevant financial relationships.

J Neurol Neurosurg Psychiatry. Published online February 18, 2010.

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