Adult-onset and late-onset multiple sclerosis in older adults in a Finnish university hospital

Background: The clinical characteristics of multiple sclerosis (MS) in individuals aged 65 years and older remain scarcely studied. This retrospective study compared late-onset MS (LOMS, onset ≥ 50 years) and adult-onset MS (AOMS, onset 18–49 years) in older adults with MS (OAwMS) aged ≥ 65 years. Methods: Data of subjects aged ≥ 65 years with a confirmed MS diagnosis and a recorded age at onset were collected from the Finnish MS registry at Tampere University Hospital, excluding individuals with paediatric-onset MS. Demographics, disease-modifying therapy (DMT) use, relapse history and Expanded Disability Status Scale (EDSS) scores were compared between LOMS and AOMS groups. Results: The cohort included 248 subjects (41 LOMS, 207 AOMS). Primary progressive MS (PPMS) was more common in LOMS when compared to AOMS (41.5% vs. 12.6% at data acquisition, p < 0.001). Among subjects with a history of relapsing-remitting MS (RRMS) (32 LOMS, 178 AOMS), DMT had been used by 25.0% and 27.5% of subjects with LOMS and AOMS, and relapses after age 65 occurred in 18.8% and 7.3% of subjects with LOMS and AOMS, respectively. Subjects with LOMS discontinued DMT at an older age when compared to those with AOMS (mean 64.0 vs. 58.8 years, p = 0.04). No age-related differences in EDSS were observed after age 65. Conclusions: PPMS was more common among subjects with LOMS. Among subjects with a current or previous diagnosis of RRMS, occasional relapses were observed after age 65 in both groups, though multiple relapses were rare. These findings support the need for individualised care of OAwMS.