Migraine headache is a relatively common, painful, and disabling disorder, and the more frequently occurring attacks associated with chronic migraine are particularly troublesome. New research suggests that healthcare providers need to be more aware of the prevalence of chronic migraine, what it is, how it is diagnosed, and who it typically affects.
There are 2 major subtypes of migraine depending on headache attack frequency. Episodic migraine headache occurs <15 days per month; whereas, chronic migraine is broadly defined as headaches on ≥15 days per month for at least 3 months. Global population estimates of chronic migraine prevalence typically range from 1.4% to 2.2%, depending on how this disorder is defined.
Past studies have demonstrated that persons with chronic migraine (relative to episodic attacks) have greater headache-related disability, worse socioeconomic status and health-related quality of life, higher rates of comorbid medical and psychiatric conditions, and increased health care resource utilization. Furthermore, each year, approximately 2.5% or more of persons with episodic migraine develop new onset chronic migraine (ie, chronification).
As part of the American Migraine Prevalence and Prevention Study, Dawn C. Buse, PhD — from the Montefiore Medical Center, Bronx, NY — and colleagues estimated the prevalence and distribution of chronic migraine in the United States population and compared the age- and sex-specific profiles of headache-related disability in persons with chronic and episodic migraine [Buse et al. 2012].
Writing in the Nov/Dec 2012 edition of Headache: The Journal of Head and Face Pain, the researchers report that they mailed surveys to a sample of 120,000 U.S. households selected to represent the overall population. Data were collected on headache frequency, symptoms, sociodemographics, and headache-related disability. Surveys were returned by 162,756 individuals aged ≥12 years, and here is a summary of results:
- 19,189 individuals (11.79%) met International Classification of Headache Disorders, 2nd Edition, criteria for migraine (17.27% of females; 5.72% of males), and 0.91% overall met criteria for chronic migraine (1.29% of females; 0.48% of males).
- Age- and sex-specific prevalence for chronic migraine peaked among persons in their 40s: 1.89% for females, 0.79% for males.
- In univariate and adjusted models, chronic migraine prevalence was inversely related to annual household income; ie, lower income groups had higher rates of chronic migraine.
- Individuals with chronic migraine had greater headache-related disability than those with episodic attacks and were more likely to be in the highest Migraine Disability Assessment Scale grade (37.96% vs 9.50%, respectively).
- Headache-related disability was highest among females with chronic migraine compared with males.
The researchers conclude that chronic migraine represents nearly 8% of all migraine cases, and within the large U.S.-based population sample in this study roughly 1% of all persons suffered from chronic migraine. Chronic migraine prevalence appears to be highest for both sexes during midlife — affecting women by greater than a 2-to-1 ratio over males — which is generally a time when work and family responsibilities are most demanding.
Additionally, individuals in households earning less than $22,500 per year had the highest rates of chronic migraine, adding pain and disability to financial stressors. Unfortunately, Buse et al. observe, these low-income individuals may not have adequate access to health care, which suggests that they may never have been diagnosed and/or may not receive appropriate treatment or care for their migraines.
The researchers advise that healthcare professionals should be aware of the rates of chronic migraine in the general population, but recognize that they may likely see a much larger percentage of patients with this condition in their particular clinical practice, especially in specialty care settings. Furthermore, the prevalence rates in this study are not peculiar to the U.S.; for example, Buse and colleagues note that similar rates have been reported in studies conducted in Germany, the Republic of Georgia, and Brazil.
CLINICAL COMMENTS: As large as this study was, there are always challenges in estimating nationwide prevalence rates based on relatively tiny samples; eg, representing less than 0.1% of the potentially affected U.S. adult population in this present research. Buse et al. also acknowledge that there may have been a response bias due to the use of a self-administered questionnaire for assessing headache subtype, frequency, severity, symptomatology, and other variables that required patients to recall their experiences during the preceding 3 months. Finally, participants in this study were somewhat older and more likely to be female than in other reported studies on this topic.
Those concerns aside, the prevalence rates in this study many not seem astoundingly high, but the overall numbers of possibly affected persons are quite significant. Using data in this study and extrapolating from the 2010 Census, there are at least 27.5 million adults (≥18 years of age) suffering from migraine headaches in the U.S., with 1.5 million women experiencing migraine more days than not each month and more than half a million men similarly experiencing chronic migraine.
Accurate diagnosis is critical in developing an optimal treatment plan for patients with chronic migraine. Buse and colleagues advise that healthcare professionals should take a thorough approach to the differential diagnosis of this condition, distinguishing it from episodic migraine. Assessment should include determining the number of days per month with and without headache to accurately assess frequency. It also should be recognized that chronic migraine can have significantly detrimental effects on occupational, academic, social, and personal functioning and well-being.
As data is this study suggest, chronic migraine also is related to significant headache-related disability. Therefore, the researchers also recommend assessing headache-related disability and quality of life as part of both the initial evaluation and ongoing management of chronic migraine. In most cases, multimodal treatment approaches would be needed to address pain and the many other burdens of chronic migraine.
REFERENCE: Buse DC, Manack AN, Fanning KM, et al. Chronic Migraine Prevalence, Disability, and Sociodemographic Factors: Results From the American Migraine Prevalence and Prevention Study. Headache. 2012;52:1456–1470 [abstract here].
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