Abstract
BACKGROUND: Sleep disorders and fatigue are common in multiple sclerosis (MS). The underlying causes are not fully understood, and prospective studies are lacking. Therefore, we conducted a prospective, observational cohort study investigating sleep quality, fatigue, quality of life, and comorbidities in patients with MS. METHODS: Patients with relapsing-remitting MS or clinically isolated syndrome treated with interferon beta-1b were followed over two years. The primary objective was to investigate correlations between sleep quality (PSQI), fatigue (MFIS), and functional health status (SF-36). Secondary objectives were to investigate correlations of sleep quality and daytime sleepiness (ESS), depression (HADS-D), anxiety (HADS-A), pain (HSAL), and restless legs syndrome (RLS). We applied descriptive statistics, correlation and regression analyses. RESULTS: 139 patients were enrolled, 128 were available for full analysis. The proportion of poor sleepers (PSQI≥5) was 55.47% at the beginning and 37.70% by the end of the study (106 and 41 evaluable questionnaires, respectively). Poor sleepers performed worse in MFIS, SF-36, ESS, HADS-D, and HADS-A scores. The prevalence of patients with RLS was low (4.5%) and all were poor sleepers. Poor sleep quality was positively correlated with fatigue and low functional health status. These relationships were corroborated by multivariable-adjusted regression analyses. ESS values and poor sleep quality at baseline seem to predict sleep quality at the one-year follow-up. No variable predicted sleep quality at the two-year follow-up. CONCLUSIONS: Our results confirm the high prevalence of poor sleep quality among patients with MS and its persistent correlation with fatigue and reduced quality of life over time. They highlight the importance of interventions to improve sleep quality. TRIAL REGISTRATION: The study was registered at clinicaltrials.gov: NCT01766063 (registered December 7, 2012). Registered retrospectively (first patient enrolled December 6, 2012).