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.