Immigrants may have a lower risk of mortality after an ischemic stroke compared to long-term residents, although the risk of recurrence of vascular events was similar in both groups, according to study results published in Neurology.
The aim of the current study was to determine the association between immigration status, ethnicity and the risk of mortality or recurrence of vascular events 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 statewide registry of data on a random sample of stroke patients treated at one of the provincial medical facilities. 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 patients born outside of Canada and after 1985 arrived were classified as immigrants. In addition, the patients were divided into three different ethnic groups: Chinese, South Asian, or other.
The sample consisted of 31,918 adults with ischemic stroke, including 2,740 immigrants (mean age 70 years; women 48%) and 29,178 long-term residents (mean age 76 years; women 49.2%).
During a median follow-up of 5 years, the risk of mortality for immigrants was lower than for long-term residents (46.1% versus 64.5%). The mortality risk decreased after adjusting the baseline characteristics and the comorbid conditions (hazard ratio) [HR]0.94; 95% CI, 0.88-1.00), but persisted in people younger than 75 years (HR 0.82; 95% CI, 0.74-1.91).
The risk of mortality was higher in South Asian immigrants than in South Asian long-term residents (HR 1.30; 95% CI 1.05-1.61), similar to that of Chinese immigrants and Chinese long-term residents (HR 0.96; 95%) CI, 0, 79-1.15) and lower among immigrants of a different ethnic origin than their long-term resident counterparts (HR, 0.89; 95% CI, 0.83-0.95) (P = 0.003 for all mortality).
Compared to long-term residents, the immigrant mortality risk was lower among immigrants from all regions except immigrants from South Asia. Study researchers observed the greatest survival benefit among immigrants from East Asia (HR 0.75; 95% CI 0.65-0.86).
The risk of recurrence of vascular events was similar among immigrants and long-term residents (adjusted HR 1.01; 95% CI 0.92-1.11). Within the ethnic groups, there was no difference in the risk of recurrence of vascular events between immigrants and long-term residents.
The study had several limitations, including determining ethnicity using surname algorithms with potential misclassification, a heterogeneous sample, and a lack of data on additional risk factors or secondary prevention measures.
“Long-term mortality after ischemic stroke is lower in immigrants and long-term residents, but similar when baseline characteristics are adjusted, and is varied by age at the time of stroke and by ethnicity,” the study’s researchers concluded.
Vyas MV, Austin PC, Fang J., Laupacis A., Silver FL, Kapral MK. Immigration status, ethnicity, and long-term outcomes after ischemic stroke. Neurology. Published online January 20, 2021. doi: 10.1212 / WNL.0000000000011451