IFNB1 and myeloid sarcoma: Here, we first describe the demographic and clinical characteristics, as well as the prescription patterns, of DMDs in patients with late-onset MS (LOMS) defined as symptoms onset after 50 years of age in comparison with adult-onset MS (AOMS) patients; and second we examine the association between exposure to interferon beta (IFNβ) and disability progression in relapsing-onset MS patients aged ≥50 (regardless of onset age) in the real-world setting in British Columbia (BC), Canada.