Disability in cluster headache is more than attack frequency - results from and validation of the English version of the Cluster Headache Impact Questionnaire (CHIQ)

Background Cluster headache (CH) is associated with high disability. The Cluster Headache Impact Questionnaire (CHIQ) is a short, disease-specific disability questionnaire first developed and validated in German. Here, we validated the English version of this questionnaire. Methods The CHIQ was assessed together with nonspecific headache-related disability questionnaires in CH patients from a tertiary headache center and an American self-help group. Results 155 active episodic and chronic CH patients were included. The CHIQ showed good internal consistency (Cronbach’s α = 0.91) and test-retest reliability (ICC = 0.93, n = 44). Factor analysis identified a single factor. Convergent validity was shown by significant correlations with the Headache Impact Test™ (HIT-6™, ρ = 0.72, p < 0.001), the Hospital Anxiety and Depression Scale (HADS depression: ρ = 0.53, HADS anxiety: ρ = 0.61, both p < 0.001), the Perceived Stress Scale (PSS-10, ρ = 0.61, p < 0.001) and with CH attack frequency ( ρ = 0.29, p < 0.001). Chronic CH patients showed the highest CHIQ scores (25.4 ± 7.9, n = 76), followed by active episodic CH and episodic CH patients in remission (active eCH: 22.2 ± 8.7, n = 79; eCH in remission: 14.1 ± 13.1, n = 127; p < 0.001). Furthermore, the CHIQ was graded into 5 levels from “no to low impact” to “extreme impact” based on the patients’ perception. Higher CHIQ grading was associated with higher attack and acute medication frequency, HIT-6™, HADS and PSS scores. Conclusion The English version of the CHIQ is a reliable, valid, and disease-specific patient-reported outcome measure to assess the impact of headaches on CH patients.