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 registry-based 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 and > 75 years) and used interaction terms to evaluate if the association between immigration status and outcomes varied with age or ethnicity.
Results — We followed 31,918 adult patients, of whom 2740 (8.6%) were immigrants, for a median follow-up of 5 years. Immigrants had a lower mortality than long-term residents (46.1% vs. 64.5%) which was attenuated after adjustment (hazard ratio 0.94; 95% confidence interval 0.88-1.00), but persisted in those aged under 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 and long-term residents, but is similar after adjustment of baseline characteristics, and it is modified by age at the time of stroke and by ethnicity.