To describe patient characteristics and assess the risk of disability worsening measured by the Expanded Disability Status Scale (EDSS) score in patients with late-onset multiple sclerosis (LOMS)

Most patients with multiple sclerosis (MS) have clinical onset between ages 20 and 40 years. However, an increasing proportion of patients are presenting with LOMS, commonly defined as disease onset after the age 50 years. Evidence on the presenting characteristics and the prognosis for these patients is scarce.

The nationwide population-based Danish Multiple Sclerosis Registry served as data source including all patients with available demographic and clinical features. Baseline characteristics were presented using descriptive statistics, as appropriate. Rates of reaching EDSS milestones were analyzed using Cox regression models stratified on baseline EDSS.

We identified 27.615 patients with MS with known year of clinical onset, of which 4678 had LOMS leaving 22.937 with non-LOMS.

In the non-LOMS group the proportion of females was 63.7% compared with 60.7% in the LOMS group. The EDSS at clinical onset was lower in non-LOMS group (2.0) compared with the LOMS group (2.8), while the number of relapses 24 months prior to diagnosis was 2.0 in the non-LOMS group and 1.5 in the LOMS group. The presenting disease course was relapsing-remitting in 90.7% of patients in the non-LOMS group and only 63.9% in the LOMS group.

Patients with LOMS had an increased rate of reaching EDSS milestones of 3 (Hazard ratio (HR): 1.1, 95% Confidence Interval (CI): 0.9-1.4), 4 (HR 1.4, 95% CI: 1.1-1.8), 6 (HR 1.6, 95% CI: 1.2-2.2) and 7 (HR 1.8, 95% CI: 1.0-3.0) when compared to the non-LOMS patients.

Onset of clinical symptoms after the age of 50 years is associated with clinical disease presentation, as well as being an important factor for the risk of EDSS worsening.