Background: Sleep disturbance is a common symptom of multiple sclerosis (MS) and knowledge about factors that contribute to poor sleep quality is scarce. Objective: The aim was to explore the differences in the prevalence and determinants of poor sleep quality in a sample of patients with MS with disease duration 5 years. Methods: We collected data from 152 consecutive patients with MS; 66 patients (78% women, averaged 37.35 +/- 10.1 years) were in the group with disease duration 5 years. Patients filled out the Pittsburgh Sleep Quality Index, the Hospital Anxiety and Depression Scale, the Multidimensional Fatigue Inventory, one item of the Incapacity Status Scale regarding bladder problems and one item of the Short Form-36 regarding pain. Multiple linear regression was used to analyze the relationship between the study variables. Results: The prevalence of poor sleep is significantly higher in patients with longer disease duration (34.8 vs. 51.2%). Anxiety, reduced motivation and mental fatigue (all p