MS risk in immigrants in the McDonald era: A population-based study in Ontario, Canada

OBJECTIVETo determine risk factors for multiple sclerosis (MS) in immigrants and to compare MS risk in immigrants and long-term residents in Ontario, Canada. METHODSWe applied a validated algorithm to linked, population-based immigration and health claims data to identify incident cases of MS in immigrants and long-term residents between 1994 and 2016. We conducted 2 multivariable Cox proportional hazards regression analyses1 analysis limited to the immigrant cohort assessing potential risk factors for developing MS, and 1 analysis comparing MS risk between immigrants and matched long-term residents (1:3 match). RESULTSWe identified 2,304,302 immigrants for the immigrant-only analysis, of whom 1,526 (0.066%) developed MS. Risk was greatest in those