Late-onset multiple sclerosis in Iran: A report on demographic and disease characteristics

•Around 1.6% of registered Iranian MS cases are in the late-onset (LOMS) category.•The age-standardized LOMS prevalence was around 75 per 100,000 people.•About half of the Iranian LOMS cases suffered relapsing-remitting course.•Nearly 23% of LOMS patients did not receive any disease-modifying treatment. Today, it is estimated that around 5% of multiple sclerosis (MS) patients are in the late-onset category (age at disease onset ≥ 50). Diagnosis and treatment in this group could be challenging. Here, we report the latest update on the characteristics of Iranian patients with late-onset MS (LOMS). This cross-sectional study used the information provided by the nationwide MS registry of Iran (NMSRI). The registrars from 14 provinces entered data of patients with a confirmed diagnosis of MS by neurologists. Patients with disease onset at or later than 50 years of age were considered LOMS. Of 20,036 records, the late-onset category included 321 patients (1.6%). The age-standardized LOMS prevalence was around 75 per 100,000 people. 215 patients (67%) were female. Median Expanded Disability Status Scale (EDSS) was 3 (interquartile range: 1.5–5). The majority of the cases (56%) suffered from relapsing-remitting (RR) course while 20% were diagnosed with primary progressive (PP) MS. Significantly higher proportion of male sex, PPMS, and higher EDSS were seen in the late-onset group compared with early-onset and adult-onset cases (p-value < 0.05). Seventy-five (23%) patients did not receive any disease-modifying treatment. The more prominent degenerative pathology of LOMS may be the underlying mechanism of the observed differences in comparison to non-LOMS. There are substantial differences and knowledge gaps regarding LOMS which could be the subject of further research.