Multiple Sclerosis After the Age of 50 Years: A Comparative Analysis of Late Onset and Adult Onset

Background and Purpose The incidence of multiple sclerosis (MS) among older patients is increasing. Some of these patients develop the disease after the age of 50 years, a condition known as late-onset MS (LOMS). This study aimed to characterize MS in older patients (50-75 years-old) by comparing LOMS with adult-onset MS (AOMS). Methods We retrospectively analyzed data from 230 patients aged 50-75 years who attended a Portuguese tertiary referral center. Results This study included 189 AOMS patients aged 58 [54-63] years (median [interquartile range]) and 41 LOMS patients aged 67 [61-70] years. Females predominated in both the LOMS (70.7%) and AOMS (75.1%) groups. Primary progressive MS was more common in LOMS than AOMS patients (19.5% vs. 8.0%, p=0.03) and these two groups had equivalent proportions of relapsing-remitting MS (53.7% vs. 59.0%, p=0.55). The Expanded Disability Status Scale (EDSS) score at the diagnosis was higher in the LOMS patients (2 [1-4], p=0.03), but the current EDSS score did not differ significantly between the LOMS and AOMS patients (3.5 [1.75-6] vs. 3 [1.5-6], p=0.86). After adjusting or matching for age and disease duration, the current EDSS scores were not significantly different in the two groups. The proportion of patients currently receiving disease-modifying therapies was higher in LOMS patients (97.6%, p=0.02). A higher proportion of patients with a later onset had infratentorial involvement at a 5-year follow-up (86.7%, p=0.01). The time to an EDSS score of 6.0 was shorter for LOMS patients. Conclusions The LOMS patients presented with higher EDSS scores at the diagnosis, reaching a level of disability not significantly different from AOMS patients of the same age group despite a shorter disease course.