Late-onset multiple sclerosis: disability trajectories in relapsing-remitting patients of the Italian MS Registry.

Background: Generally infrequent, multiple sclerosis (MS) with late onset (LOMS) is characterized by an onset over the age of 50 and a mainly progressive course, while relapsing-remitting (RR) forms are less frequently observed and explored. This study aimed to characterize a large cohort of MS patients with RRMS at onset to assess the baseline factors related to the worst disability trajectories and explore the role of LOMS.

Methods: The data were extracted from the Italian MS Register (IMSR). Disability trajectories, defined using at least two and up to twenty expanded disability status scale (EDSS) assessments annually performed, were implemented using group-based trajectory models (GBTMs) to identify different groups with the same trajectories over time. MS profiles were explored using multinomial logistic regression.

Results: A total of 16,159 RR patients [1012 (6.26%) presented with LOMS] were analyzed. The GBTM identified four disability trajectories. The group with the most severe EDSS trend included 12.3% of the patients with a mean EDSS score > 4, which increased over time and exceeded 6 score. The group with medium severity EDSS trend comprised 21.9% of the patients and showed a change in EDSS > 3 scores over time. The largest group with 50.8% of patients reported a constant EDSS of 2 score. Finally, the benign group comprised 14.9% of the patients with a low and constant EDSS of 1 score over time. The probability of being in the worst groups increased if the patient was male; had LOMS or experienced brainstem, spinal, or supratentorial symptoms.

Conclusions: Four MS severity profiles among RRMS patients in the IMSR have been reported, with LOMS being associated with a rapid worsening of EDSS scores. These findings have important implications for recognizing and managing how older age, aging, and age-related factors interact with MS and its evolution.