Incidence of Multiple Sclerosis in Uruguay: A Prospective Population-Based Study.

Background: The worldwide incidence of multiple sclerosis (MS) is estimated at 0.5-10 cases per 100,000 person-years and is probably increasing. In 2014, a previous study estimated the incidence of multiple sclerosis in Uruguay at 1.2 cases per 100,000 person-years.

Objectives: We conducted an observational, prospective, population-based study to determine MS incidence from diagnosis in Uruguay.

Methods: The population studied included people older than 18 years of age who were living in Uruguay between July 1, 2019, and June 30, 2021. The diagnosis was based on 2017 McDonald criteria. Multiple data sources were employed including neurologists, magnetic resonance imaging centers, laboratories performing oligoclonal band testing, neurophysiology laboratories, neurorehabilitation centers, the institution Fondo Nacional de Recursos, and the MS Patients' Association of Uruguay (EMUR). The capture-recapture method was used to estimate incidence.

Results: 155 new MS cases were confirmed after review. The median age was 35 (range 18-62). Thirteen patients (8.38%) were diagnosed with late-onset MS. The crude incidence rate was 2.89 cases per 100,000 person-years, 3.95 among females, and 1.72 among male patients. The incidence rate estimated using the capture-recapture method was 3.18 (95% CI: 3.02-3.34).

Conclusions: According to the Atlas of MS, Uruguay has a low incidence rate (2.0-3.99), even though it is one of the highest in Latin America. Our country aligns with the global trend of increasing incidence. Age and sex distribution were similar to other studies, with a high incidence of patients with late-onset multiple sclerosis. The capture-recapture method confirms the exhaustivity of our investigation.