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.