Background: Sleep disturbances in the multiple sclerosis (MS) population are increasingly recognized, but the factors driving this association remain understudied. This study aimed to determine the prevalence and associations of poor sleep quality in the relapsing–remitting MS (RRMS) population receiving disease-modifying therapy (DMT). Methods: We conducted a cross-sectional study that enrolled 399 individuals diagnosed with RRMS on DMT. Data on patient demographics, clinical presentation, and treatment were systematically evaluated. Sleep-related outcomes were assessed using validated questionnaires—the Pittsburgh Sleep Quality Index (PSQI), Insomnia Severity Index (ISI), Epworth Sleepiness Scale (ESS), Fatigue Severity Scale (FSS), STOP-Bang questionnaire, and Hamilton Anxiety Rating Scale (HAM-A). Independent associations of poor sleep were examined using log-binomial regression to estimate risk ratios (RR). Results: Poor sleep was reported in 42% of the participants in our cohort. In multivariable analysis, only insomnia severity (RR = 1.07; 95% CI 1.05–1.09, p < 0.001) and anxiety (RR = 1.02; 95% CI 1.01–1.04, p = 0.001) remained independently associated with poor sleep. Conclusions: Sleep disturbances are common among patients with RRMS. Insomnia severity and anxiety, rather than demographic or disease-related characteristics, showed independent associations with impaired sleep. Routine screening and targeted interventions addressing insomnia and anxiety may improve sleep quality and, consequently, overall quality of life in this population.

Background: Sleep disturbance is common in multiple sclerosis (MS), but its relationship with relapse status remains insufficiently defined. This study examined whether poorer subjective sleep quality was associated with relapse status in patients with relapsing-remitting multiple sclerosis. Methods: This propensity score–matched nested case–control analysis included 132 patients with relapsing-remitting MS selected from 473 consecutively evaluated patients at a tertiary multiple sclerosis centre. Patients in relapse were matched 1:1 to patients in remission by age, sex, disease duration, Expanded Disability Status Scale score, disease-modifying therapy duration and efficacy class, and relapse in the previous year. Sleep quality and related symptoms were assessed using validated questionnaires. Results: Patients in relapse were more frequently classified as poor sleepers than those in remission (59.1% vs. 36.4%; p = 0.009). In the double-adjusted logistic regression model, higher Pittsburgh Sleep Quality Index scores were independently associated with relapse status (OR = 1.16; 95% CI 1.02–1.32; p = 0.023), whereas the remaining variables were not independently associated with relapse status. Conclusions: Poorer subjective sleep quality was independently associated with relapse status in relapsing-remitting MS, supporting sleep disturbance as a relapse-associated clinical feature rather than a proven causal risk factor.