Immigration Status, Ethnicity, and Long-term Outcomes Following Ischemic Stroke

Objective To assess the association between immigration status and ethnicity and the outcomes of mortality and vascular event recurrence following ischemic stroke in Ontario, Canada. Methods We conducted a retrospective cohort study using linked administrative and clinical registrybased data from 2002 to 2018 and compared hazards of all-cause mortality and vascular event recurrence in immigrants and long-term residents using inverse probability of treatment weighting accounting for age, sex, income, and comorbidities. We stratified analyses by age (75 years) and used interaction terms to evaluate whether the association between immigration status and outcomes varied with age or ethnicity. Results We followed 31,918 adult patients, of whom 2,740 (8.6%) were immigrants, for a median follow-up of 5 years. Immigrants had lower mortality than long-term residents (46.1% vs 64.5%), which was attenuated after adjustment (hazard ratio [HR] 0.94; 95% confidence interval [CI] 0.88-1.00), but persisted in those younger than 75 years (HR 0.82; 0.74-0.91). Compared to their respective ethnic long-term resident counterparts, the adjusted hazard of death was higher in South Asian immigrants, similar in Chinese immigrants, and lower in other immigrants (p value for interaction = 0.003). The adjusted hazard of vascular event recurrence (HR 1.01; 0.92-1.11) was similar in immigrants and long-term residents, and this observation persisted across all age and ethnic groups. Conclusions Long-term mortality following ischemic stroke is lower in immigrants than in long-term residents, but is similar after adjustment for baseline characteristics, and it is modified by age at the time of stroke and by ethnicity.