The clinical and public health implications and risks of widening the definition of chronic migraine.

The definition of chronic migraine has long been debated. Recently, it was suggested to define subjects with at least 8/migraine days as chronic migraine; that is, incorporating so-called high frequency episodic migraine (eight or more migraine days but less than 15 headache days per month). We addressed the possible problems that might arise based on this proposal accounting for clinical, pathophysiological, impact and public health aspects. Defining chronic migraine on the basis of headache frequency alone does not account for clinical and pathophysiological aspects, as well as for the impact of chronic migraine in terms of disability and quality of life. Moreover, it is potentially harmful for patients in terms of allocation of resources. These issues are discussed in the present manuscript, and we support the idea of defining high frequency episodic migraine as an independent entity as a viable path to follow.