BACKGROUND: Multiple system atrophy (MSA) is a progressive neurodegenerative disorder characterized by parkinsonism, cerebellar ataxia, autonomic dysfunction, and sleep disturbances, such as rapid eye movement sleep behavior disorder (RBD). The association between sleep disturbances, including RBD, and decreased quality of life (QOL) in patients with MSA has not been elucidated. We aimed, therefore, to evaluate this association in individuals with MSA. METHODS: We assessed a total of 34 patients with MSA (44.1 % male
61.8 % MSA with predominant cerebellar ataxia) for sleep disturbances, RBD, and QOL using the Parkinson's Disease Sleep Scale-2 (PDSS-2), RBD Screening Questionnaire (RBDSQ), and Parkinson's Disease Questionnaire-39 (PDQ-39). Multiple regression analyses were conducted with the Summary Index (SI) of PDQ-39 total and each domain as dependent variable and age, sex, urinary dysfunction, and the PDSS-2 total, sleep, motor, parkinsonism, and the RBDSQ scores as independent variables. RESULTS: The rate of PDSS-2 scores ≥ 15 was 41.2 %, while that of RBDSQ scores ≥ 5 was 17.6 %. Multiple regression analyses revealed that the PDSS-2 total score significantly contributed to increase in the SI of PDQ-39 total (β = 0.646, P <
0.001), mobility (β = 0.663, P <
0.001), activities of daily living (β = 0.650, P <
0.001), emotional well-being (β = 0.426, P = 0.019), and bodily discomfort (β = 0.566, P <
0.001). CONCLUSION: We demonstrated a strong relationship between the sleep disturbances and worsening QOL in patients with MSA. Healthcare providers should also focus on sleep disturbances when managing patients with MSA.