Interictal Burden of Cluster Headache: Results of the EUROLIGHT Cluster Headache Project, an Internet-Based, Cross-Sectional Study of People With Cluster Headache

OBJECTIVE The aim of this study was to measure the interictal burden (IIB) associated with cluster headache (CH). BACKGROUND CH is characterized by an alternation of excruciatingly painful attacks and pain-free periods. Absence of pain does not necessarily imply absence of symptoms, though. Some may persist or improve more slowly than pain; others may arise in between attacks. METHODS Participants filled out an online survey based on the EUROLIGHT questionnaire. Inclusion criteria were a reported diagnosis of CH and residency in a European country; exclusion criteria were refusal to give informed consent and to complete the questionnaire. RESULTS Most of the burden was related to higher headache frequencies: ongoing symptoms despite pain freedom, impaired autonomy due to avoidance of triggers, reluctance to tell others about the disease, and the feeling of not being understood by family and friends, employers and colleagues. Irreversible, potentially accumulating burden may occur if headache frequency is high; examples are impairment of career options, relationships, and family planning issues. Worrying about future attacks and avoiding potential triggers occur independently from attack frequency and disease duration. There were no differences between the in-bout and the out-bout period among participants with episodic CH. Participants with chronic CH reported greater IIB. CONCLUSIONS Even between attacks CH can have a huge and potentially irreversible impact on life. Different types of IIB were identified, all of which may contribute to the total burden of disease. As cumulative burden might be irreversible, prevention strategies need to be developed