Insomnia moderates the association between recurrent seizures and emotional instability in persons with epilepsy

Purpose: We investigated the moderating effect of sleep disturbance on the association between seizure recurrence and emotional instability in patients with epilepsy, independent of psychological distress. Methods: This was a cross-sectional study. Patients completed the short form of the Affective Lability Scale (ALS-18), Insomnia Severity Index (ISI), Patient Health Questionnaire-9 (PHQ-9), and Generalized Anxiety Disorder-7 (GAD-7). A stepwise linear regression analysis and an analysis of covariance with an interaction term were performed. Results: A total of 171 subjects (63.2% men) were included. The mean ALS-18 score was 15.6 ± 11.3. An ISI ≥ 15, PHQ-9 ≥ 10, and GAD-7 ≥ 7 were noted in 20.5%, 18.1%, and 23.4% of subjects, respectively. A stepwise linear regression analysis found that recurrent seizures in the last year, an ISI ≥ 15, a GAD-7 ≥ 7, and use of levetiracetam were significant and independent factors that were positively associated with higher ALS-18 scores. The coefficient of determination for the model was 0.331. The interaction between recurrent seizures and an ISI ≥ 15 had a significant effect on the ALS-18 scores (F = 6.812, p = 0.010, partial eta² = 0.040). An ISI ≥ 15 was associated with ALS-18 scores in patients without seizure recurrence (p < 0.001). This association almost reached significance (p = 0.084) in those with recurrent seizures. In contrast, the presence of recurrent seizures was associated with ALS-18 scores in patients with an ISI < 15 (p < 0.001), but not in those with an ISI ≥ 15 (p = 0.360). Conclusions: The significant interaction between insomnia and seizure status may have an effect on emotional instability. These findings have clinical implications in the development of potential interventions for emotional instability in patients with epilepsy.