In a clinical paper published in Cephalalgia, researchers argue that chronic migraine should not be solely defined by headache frequency alone, as this definition ignores the clinical and pathophysiological aspects of chronic migraine and can be potentially harmful to patients in regard to allocation of treatment resources.
According to the International Classification of Headache Disorders-3 criteria, chronic migraine is differentiated from episodic migraine by the threshold of the number of headache days per month. In chronic migraine, the threshold is headaches that occurred ≥15 days per month in the past 3 months, with ≥8 of those headache days consisting of migraine-like features. It has been argued that the definition of chronic migraine should be merged with that of high-frequency episodic migraine, due to the 2 conditions’ similarities in terms of disability, comorbidities, and treatment options.
Despite this argument, authors of the clinical correspondence in Cephalalgia note that this merger of definitions does not take into account headache frequency, quality of life outcomes, and economic and public health issues. Additionally, there are some data that show chronic migraine features 8 to 10 more headaches per month than high-frequency episodic migraine, and chronic migraine is associated with worse outcomes.
The expansion of the definition of chronic migraine has the potential to contribute to greater costs associated with migraine disorders, because the number of patients who will require access to the same specific prophylactic therapies will expectedly increase. This increase, the authors point out, would more than likely not reduce the consumption of acute treatments.
Additionally, there is a risk of hyperselection of the most severe cases for treatment consideration in universal coverage systems, whereas only the most affluent patients will likely benefit in insurance-based systems.
The authors concluded that although the arbitrary classification of migraine by frequency may support treatment decisions, this action does not necessarily provide clear identification of patient subsets who are in the greatest need of therapy. It may be more beneficial, they argue, to perform research that will define high-frequency episodic migraine as an independent entity. “Only then we will be able to look into treatment priority targets aiming to intercept the chronification process and its overall burden from a perspective of economic, personal, and social sustainability of new therapeutic options,” they wrote.
Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.
Guglielmetti M, Raggi A, Ornello R, et al. The clinical and public health implications and risks of widening the definition of chronic migraine [published online December 15, 2019]. Cephalalgia. doi:10.1177/0333102419895777