Correlates of interictal burden in episodic and chronic migraine: associations with disability, sleep quality, anxiety, and depression

This study aimed to evaluate clinical and psychometric correlates of interictal burden measured by The Migraine Interictal Burden Scale-4 (MIBS-4) in prophylaxis-free, first-admission migraine patients using a two-model comparative regression strategy. Two hundred patients diagnosed according to ICHD-3 (The International Classification of Headache Disorders, 3rd edition) criteria were included (CM: n = 100, EM: n = 100; age: 27.67 ± 8.18 years; female: 72.5%); this 1:1 artificial balance was intentionally established for comparative analysis rather than reflecting true outpatient prevalence. MIBS-4, Headache Impact Test-6 (HIT-6), Pittsburgh Sleep Quality Index (PSQI), Generalized Anxiety Disorder-7 (GAD-7), and Patient Health Questionnaire-9 (PHQ-9) were administered. The frequency variable was reported strictly as monthly headache days (MHDs); the absence of monthly migraine days (MMD) data limits direct generalizability. PSQI scores were operationally categorized as normal sleep quality (≤ 5), poor sleep quality (6–10), and severe sleep disturbance (≥ 11). Sensitivity analyses were performed using HC3 robust standard errors. MIBS-4, HIT-6, GAD-7, PHQ-9, PSQI, and MHDs were significantly higher in CM than in EM. Among the entire cohort, 14 patients had normal sleep quality (7%), 104 had poor sleep quality (52%), and 82 had severe sleep disturbance (41%). Severe sleep disturbance was more frequent in CM than EM (48/100 [48%] vs. 34/100 [34%]; dichotomous comparison p = 0.044; three-tier distribution p = 0.062). Migraine type was the strongest independent correlate in Model A (B = 3.000, 95% CI [2.041, 3.960], β = 0.559, p < 0.001), whereas MHDs showed a comparable association in Model B (B = 0.206, 95% CI [0.132, 0.279], β = 0.463, p < 0.001). The models explained approximately one-third of MIBS-4 variance (R²: 0.334 and 0.312). Psychometric variables were associated with MIBS-4 in bivariate analyses (though relatively weakly for PHQ-9 and PSQI) but did not retain independent associations in multivariable models. In this prophylaxis-free first-admission cohort, MIBS-4 burden was most consistently associated with the migraine type/MHDs severity axis. However, the unexplained variance suggests that additional unmeasured factors, such as stigma, interictal sensory symptoms, general well-being, socioeconomic factors, access to care, and medication overuse, may contribute to interictal burden. Crucially, medication overuse headache (MOH) status was not assessed, precluding any causal attribution; thus, the observed effect of MHDs may be partially attributable to unmeasured medication overuse.