Chronic Migraine Definition and High-Frequency Episodic Migraine Inclusion

Individuals with ≥8 and <15 monthly headache days experience the same disability as those with chronic migraine as defined in the International Classification of Headache Disorders (ICHD)-3, and this group should be included in the revised diagnostic criteria for chronic migraine, according to a study published in Cephalalgia.

This study included 174 individuals with chronic migraine (defined by ICHD-3) and 176 with high-frequency episodic migraine (HFEM; defined as ≥8 but <15 headache days per month). In a cohort from the Danish Headache Center, individuals and their relatives with chronic migraine were compared with Danish individuals with HFEM. The study researchers examined Danish registries to determine the relative socioeconomic impacts for these groups. To assess the generalizability of the proposed chronic migraine diagnostic criteria among different populations, a medical student dataset from Russia (n=1042) was used. Normally distributed data were compared using t-tests and standard deviations, while non-normally distributed data were compared using a nonparametric test. Socioeconomic factor analysis was performed using logistic regression.

Those with chronic migraine did not differ significantly from those with HFEM in terms of migraine attack frequency; receipt of sickness benefit; cash assistance; or rehabilitation benefit; comorbidities with the exception of asthma/allergy and epilepsy. Triptan purchases were significantly higher among those with HFEM than with chronic migraine (P =.01), and those with chronic migraine received higher rates of early retirement pension than those with HFEM (33.5% vs 20.8%, respectively).

Limitations to this study include a lack of more refined subdivisions for the HFEM subgroup; associations with medication use, disability, and social variables; and the inclusion of individuals in the chronic migraine group who did not experience ≥15 monthly headache days.

The study researchers concluded that “[patients] with migraine on eight or more days but not 15 days with headache a month are as disabled as patients with ICHD-3 defined [chronic migraine].” They added that the revised chronic migraine diagnostic criteria should include this group. 

Reference

Chalmer MA, Hansen TF, Lebedeva ER, Dodick DW, Lipton RB, Olesen J. Proposed new diagnostic criteria for chronic migraine [published online September 22, 2019]. Cephalalgia. doi: 10.1177/0333102419877171