Immigrants may be at a lower risk for mortality after ischemic stroke compared with long-term residents, although the risk for vascular event recurrence was similar in both groups, according to study results published in Neurology.
The objective of the current study was to determine the association between immigration status, ethnicity, and the risk for mortality or vascular event recurrence in patients with a history of ischemic stroke in Ontario, Canada.
This retrospective cohort study was based on data from the Ontario Stroke Registry, a province-wide registry with data on a random sample of patients with stroke treated in one of the medical institutions in the province. Study researchers identified patients with ischemic stroke between April 1, 2002 and March 31, 2013. Patients born in Canada and those who moved to Canada before 1985 were classified as long-term residents, while those who were born outside of Canada and arrived after 1985 were classified as immigrants. In addition, patients were categorized into 3 different ethnic groups: Chinese, South-Asian, or other.
The study sample included 31,918 adults with ischemic stroke, including 2740 (median age, 70 years; women, 48%) immigrants, and 29,178 long-term residents (median age, 76 years; women, 49.2%).
During a median follow-up of 5 years, the mortality risk was lower for immigrants, compared with long-term residents (46.1% vs 64.5%, respectively). The mortality risk decreased after adjustment for baseline characteristics and comorbid conditions (hazard ratio [HR], 0.94; 95% CI, 0.88-1.00), but persisted in those who were younger than 75 years old (HR, 0.82; 95% CI, 0.74-0.91).
The mortality risk was higher among South-Asian immigrants than among South-Asian long-term residents (HR, 1.30; 95% CI, 1.05-1.61), similar in Chinese immigrants and Chinese long-term residents (HR, 0.96; 95% CI, 0.79-1.15), and lower in immigrants of other ethnic origin than their long-term resident counterparts (HR, 0.89; 95% CI, 0.83-0.95) (P =.003 for all-cause mortality).
Compared to long-term residents, the risk for mortality among immigrants was lower in immigrants from all regions, except for immigrants from South Asia. Study researchers observed the greatest survival advantage in immigrants from East Asia (HR, 0.75; 95% CI, 0.65-0.86).
The risk for vascular event recurrence was similar in immigrants and long-term residents (adjusted HR, 1.01; 95% CI, 0.92-1.11). Within ethnic groups, there was no difference in the risk for vascular event recurrence between immigrants and long-term residents.
The study had several limitations, including determining ethnicity using surname algorithms with potential misclassification, a heterogeneous study sample, and missing data on additional risk factors or secondary preventative measures.
“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,” concluded the study researchers.
Vyas MV, Austin PC, Fang J, Laupacis A, Silver FL, Kapral MK. Immigration status, ethnicity, and long-term outcomes following ischemic stroke. Neurology. Published online January 20, 2021. doi:10.1212/WNL.0000000000011451