Abstract
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.