Late-onset versus adult-onset multiple sclerosis: A comparative analysis of clinical, radiological, and confirmed disability progression.

BACKGROUND: Multiple sclerosis (MS) is a chronic, immune-mediated disorder of the central nervous system (CNS). In Egypt, its occurrence is approximately 13.7 per 100,000 inhabitants. The average age of onset for relapsing-remitting MS (RRMS) is between the second and fourth decades of life. OBJECTIVES: To determine the differences in clinical characteristics, disease course, and progression between adult-onset MS (AOMS) and late-onset MS (LOMS). SUBJECTS AND METHODS: This observational comparative study was conducted on patients diagnosed with MS according to the revised McDonald criteria at the MS Clinic of Kasr Al-Ainy Hospital, Cairo University. Patients with AOMS (111) and LOMS (54) were compared based on various parameters, with longitudinal assessment of disease progression. RESULTS: The LOMS group had a significantly higher proportion of patients with primary progressive MS (PPMS) than the AOMS group. Additionally, the LOMS group had significantly fewer relapses, a lower annualized relapse rate (ARR), a longer disease duration and longer time to treatment, and a higher baseline EDSS score than the AOMS group (P < 0.05). Regarding baseline brain MRI findings, a higher percentage of LOMS patients had infratentorial lesions (P = 0.0002). LOMS patients also experienced earlier confirmed disability progression (CDP). The median time to CDP was 71 months (95% CI, 31.7-94.4) in the LOMS group and 113.6 months (95% CI, 81.2-142.0) in the AOMS group. In a stepwise Cox proportional hazards regression analysis, LOMS status remained significantly associated with CDP, (HR = 1.89, 95% CI 1.05-3.42, P = 0.035), indicating an approximately 89% higher risk of CDP compared with AOMS. CONCLUSION: The present study adds data from an Egyptian cohort and highlights significant differences between AOMS and LOMS. Patients with LOMS tend to have a higher prevalence of PPMS, a greater burden of comorbidities, higher baseline disability, lower relapse activity, and a shorter time to CDP.