Epidemiologic Trends of Multiple Sclerosis in Puerto Rico (2013–2020)

Background: Previous studies have demonstrated higher multiple sclerosis (MS) incidence and prevalence in Puerto Rico (PR) than in other Caribbean and Latin American countries. Our objectives are to update the epidemiologic trends in MS incidence and prevalence rates for PR from 2017 through 2020 and compare them to prior rate data from 2013 to 2016.Methods: We used the Puerto Rico MS Foundation's registry (PRMS Registry) data to identify all newly diagnosed MS cases between January 2017 and December 2020. The study population included 568 MS patients, 406 women and 162 men living in PR. All individuals were 18 years and older and met the 2017 revised McDonald criteria for MS diagnosis. In addition, age-and sex-standardized incidence rates were estimated.Results: A total of 568 new MS cases were diagnosed in Puerto Rico between 2017 and 2020. The 2020 MS cumulative prevalence for Puerto Rico was 95.3/100,000 (95% CI: 91.6, 99.1), higher than previously reported. The age-and sex-standardized MS incidence rate for Puerto Rico decreased from 6.5/100,000 (2017) to 6.3/ 100,000 (2020). The annual age-standardized MS incidence rates declined for females: from 9.5/100,000 (2017) to 8.2/100,000 (2020) but increased for males from 3.6/100,000 to 4.6/100,000 during the same period.Conclusion: These incidence and prevalence rates are among the highest reported among Caribbean and Latin American countries. A peak in the age-and sex-standardized MS incidence rate was observed after hurricane Maria (2018) and a decline during the first year of the COVID-19 pandemic (2020). Further investigation is needed to determine whether there was a causal relationship between the fluctuations observed and those natural events.