Academy of Medical Sciences of I.R. Iran Archives of Iranian Medicine 1029-2977 25 11 2022 11 01 Clinical and Epidemiological Aspects of Late Onset Multiple Sclerosis in East-Azerbaijan, Iran; A Population-Based Study 725 729 10.34172/aim.2022.114 EN Ehsan Nasiri https://orcid.org/0000-0002-9679-5623 Amirreza Naseri https://orcid.org/0000-0001-9723-0109 Pouya Abbasgholizadeh https://orcid.org/0000-0003-4989-6509 Ali Fahidi https://orcid.org/0000-0001-6722-4357 Mahnaz Talebi https://orcid.org/0000-0002-7613-3913 Journal Article 10.34172/aim.2022.114 2021 05 08 2021 10 31 Background: Late-onset multiple sclerosis (LOMS) is defined as symptoms initiating at an age above 50. Objective: This study aims to determine the clinical and epidemiological aspects of LOMS in East-Azerbaijan province, Iran. Methods: This population-based study recruited nearly all MS patients to the end of 2020, who were diagnosed at age≥50, by referring to the only local MS registry center. We investigated prevalence, sex, age-of-onset, first clinical presentation, family history, and gap of diagnosis. Also, we compared the disease characteristics between male and female cases. Results: Out of 4905 total cases of MS, 217 cases (4.42%) were LOMS. The mean age of onset was 53.80±3.41 years with a maximum age of 68 years. The most common age group of the patients was 50 to 55 years (69.1%). The frequency by sex of LOMS in females (150) was greater than males (67). Positive family history was seen in 6.17%, and in 41% of the patients, the disease was diagnosed in a timely manner. Early symptoms were motor (31.3%), sensory (24.8%), optic neuritis (23%), cerebellar symptoms (13.8%), and brainstem symptoms (6.9%). The first presentation of the disease was different between male and female cases (P-value<0.01). Motor symptoms were the most prevalent first clinical presentation in female cases (37.6%), while in male cases, cerebellar symptoms (25.8%) were the most common. Conclusion: LOMS is not a rare condition. Increasing knowledge in the diagnosis, as well as increasing awareness of the disease in the general population, leads to early diagnosis of LOMS and prevention of consequences.