Latitudinal prevalence gradient of multiple sclerosis in Latin America

Background: Multiple sclerosis (MS) has a unique geographical distribution that reflects both genetic and environmental factors. Many studies have shown a positive correlation between MS frequency and latitude across both large and small geographical regions. However, scarce data have been published on the epidemiology of MS in Latin America and no study has evaluated latitudinal variation. Objective: To evaluate the effect of latitude on MS prevalence in Latin America. Methods: We conducted a systematic review of MS prevalence during January 2011. Prevalence rates were collected from eligible publications. The effect of latitude on prevalence was analyzed using linear regression. Results: A total of ten studies were eligible for analysis, corresponding to six countries, spanning from Panama to Argentina. The crude prevalence of MS ranged from 0.75 to 21.5 per 100,000. We found a strong and significant association between prevalence and latitude (r(2) 0.8; p < 0.001) and determined an increase in prevalence of 0.33 per 100,000 per degree latitude. Conclusion: Our findings suggest a latitudinal prevalence gradient of MS in Latin American countries between Panama and Argentina.