Disability and Relapse Risk in Late-Onset Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease.

Importance: The impact of late onset in myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is still controversial. Objective: To investigate the association of late onset MOGAD with moderate disability and relapse in Korean patients. Design, Setting, and Participants: This nationwide, multicenter, retrospective cohort study included adult patients with a diagnosis of MOGAD according to the 2023 international diagnostic criteria between August 2018 and September 2024 across 28 hospitals in South Korea. Exposure: Age at onset of MOGAD, categorized into adult-onset MOGAD (AO-MOGAD; 18-49 years) and late-onset MOGAD (LO-MOGAD; ≥50 years). Main Outcomes and Measures: The primary outcomes were time to first relapse in patients with a disease duration of 12 or more months and moderate disability, defined as Expanded Disability Status Scale (EDSS) score of 3 or greater at last follow-up. Results: A total of 350 patients (mean [SD] age at onset, 43.2 [15.0] years; 189 female [54.0%]) with a median (IQR) baseline EDSS of 3.0 (2.0-4.0) were included, with 124 patients (35.4%) with LO-MOGAD and 226 patients (64.6%) with AO-MOGAD. The LO-MOGAD group had less frequent brain involvement than the AO-MOGAD group at onset (26 patients [21.0%] vs 75 patients [33.2%]; P = .02) and during the disease course (28 patients [22.6%] vs 95 patients [42.0%]; P < .001), while optic neuritis or myelitis was comparable between the 2 groups. The LO-MOGAD group showed more frequent monophasic course (55 of 95 patients [57.9%] vs 75 of 188 patients [39.9%]; P = .004), but higher EDSS score at last follow-up (median [IQR], 2.0 [1.0-2.0] vs 1.0 [0.0-2.0]; P < .001) compared with those in the AO-MOGAD group. However, late onset was not significantly associated with the time to first relapse in multivariable analysis (adjusted hazard ratio, 0.72; 95% CI, 0.48-1.08; P = .11), which was consistent after propensity score matching. By contrast, late onset was associated with a significantly higher risk of moderate disability at the last follow-up (adjusted odds ratio, 2.84; 95% CI, 1.39-5.80; P = .004). Conclusions and Relevance: In this cohort study of MOGAD, late onset was not associated with a risk of relapse but with a higher risk of moderate disability at follow-up. Prospective studies with longer follow-up periods are warranted to better understand and manage patients with late-onset disease.