Objective: To describe the characteristics of late-onset multiple sclerosis (MS) (LOMS, 50+ years) vs adult-onset MS (AOMS, 16 to <50 years) and examine prognosis and associated risk factors.

Methods: Patients with definite MS, onset prior to July 1988, registered with a BCMS clinic before July 1998, with at least one Expanded Disability Status Scale (EDSS) score, were selected from the longitudinal population-based British Columbian (BC) MS database. Clinical and demographic characteristics were compared between LO and AOMS. Progression was measured as time to reach sustained EDSS 6 and potential risk factors examined were sex, disease course (primary progressive [PP] vs relapsing [R]), and onset symptoms.

Results: Of those eligible (n = 2,837), LOMS comprised 132 (4.7%), with PPMS predominating (54.5% vs 10.6% in AOMS, p < 0.0005). Motor onset symptoms were more prevalent in LOMS and sensory and optic neuropathy more prevalent in AOMS (p < 0.0005). AOMS averaged 27.7 years (95% CI: 26.3 to 29.1) to EDSS 6 from onset vs 16.9 years (95% CI: 9.0 to 24.8) in LOMS, p < 0.0005. However, AOMS was associated with a younger age at EDSS 6 (58.4 years [95% CI: 57.1 to 59.6] vs 71.2 years [95% CI: 65.2 to 77.3] in LOMS, p < 0.0005). There were no differences in progression between AO or LO for those with PPMS (p = 0.373) or R-MS (p = 0.438), although considerable variation was observed.

Conclusions: Late-onset multiple sclerosis (LOMS) is not necessarily associated with a worse outcome: first, progression in the primary progressive or relapsing patients differed little between late-onset vs adult-onset; secondly, those with LOMS were older when reaching Expanded Disability Status Scale 6. The disease course has a far greater implication for disease prognosis than the presence of LOMS.