Measuring interictal burden among people affected by migraine: a descriptive survey study

BACKGROUND: Previous research has extensively documented the impact of migraine episodes (‘ictal’) on patients’ health-related quality of life. Few studies have looked at the impact of migraine on migraine-free days (‘interictal’). This study was designed to describe interictal burden of migraine in a mixed group of people affected by migraine and to explore patient characteristics associated with interictal burden. METHODS: People with migraine in the United States (US) and Germany were recruited for a cross-sectional online survey, including a subgroup treated with calcitonin gene-related peptide (CGRP) monoclonal antibody (mAb). The survey included the Migraine Interictal Burden Scale (MIBS-4), Headache Impact Test (HIT-6), and items measuring patient demographics, clinical and treatment background. Data were analyzed using descriptive statistics and linear regression. RESULTS: Five hundred six people with migraine completed the survey (US: n = 257; Germany: n = 249), of whom 195 had taken a CGRP mAb for three or more months. Participants had a mean of 8.5 (SD = 6.4) Monthly Migraine Days (MMD) and 10.4 (SD = 7.1) Monthly Headache Days (MHD). The mean MIBS-4 score was 6.3 (SD = 3.4), with 67% reporting severe interictal burden (MIBS-4: ≥5). The mean HIT-6 score was 65.3 (SD = 6.0), with 86% reporting severe migraine impact (HIT-6: ≥60). MIBS-4 was correlated with the HIT-6 (r = 0.37), MMD and MHD (both r = 0.27). The HIT-6, MMD, MHD, CGRP mAb treatment, and depression all had an independent positive association with the MIBS-4. CONCLUSION: Two-thirds of the study sample reported substantial interictal burden. Whilst interictal burden was associated with migraine frequency and impact of migraine attacks, study results also show it represented a distinct aspect of the overall disease burden. Study findings further indicate unique associations between interictal burden and depression. A unique positive association between interictal burden and CGRP mAb treatment suggests a remaining unmet need among people affected by migraine treated with CGRP mAb.