Background: People with multiple sclerosis (MS) present varying degrees of disability throughout their disease course. The Multiple Sclerosis Severity Score (MSSS) and the Age-Related Multiple Sclerosis Severity Score (ARMSSS) adjust the Expanded Disability Status Scale (EDSS) according to disease duration and age, respectively. These measures could be useful for quantifying MS severity and as health outcome indicators for benchmarking in population-based settings. The aim of this study was to describe the severity of MS in our health district using the MSSS and ARMSSS and to assess their consistency over time.

Methods: This population-based study included patients from our health district who were diagnosed with MS according to the 2010 McDonald criteria, had a disease duration of at least one year and were followed up in our MS unit. Sex, age at onset, disease duration, clinical course, age and irreversible EDSS at the last follow-up visit were collected, and the MSSS and ARMSSS were calculated at two time points: 2017 and 2020.

Results: One hundred seventy-seven patients were included in 2017, and 208 in 2020. The prevalence of MS was 90 and 104 per 100,000 inhabitants, respectively. The median MSSS was 1.77 (IQR 0.76-4.28) in 2017 and 2.03 (IQR 0.82-4.36) in 2020. The median ARMSSS was 2.90 (IQR 1.47-5.72) in 2017 and 2.93 (IQR 1.51-5.56) in 2020. No significant differences were found.

Conclusions: According to the MSSS and ARMSSS, the severity of MS in our area is mild, and these instruments are consistent. These measures could be reliable health outcome measures.