Incidence of Stroke in Immigrants to Canada: A Province-wide Retrospective Analysis

Determinants, Prevention, and Incidence of Cardiovascular Disease Among Immigrant and Refugee Populations

Immigration policies shape the composition, socioeconomic characteristics, and health of migrant populations. The health of migrants is also influenced by a confluence of social, economic, environmental, and political factors. Immigrants and refugees often face various barriers to accessing health care because of factors such as lack of familiarity with navigating the health care system, language barriers, systemic racism, and gaps in health insurance. Social determinants of health and access to primary care health services likely influence the burden of cardiovascular risk factors among immigrants. The relatively low burden of many cardiovascular risk factors in many immigrant populations likely contributes to the generally lower incidence rates of acute myocardial infarction, heart failure, and stroke in immigrants compared with nonimmigrants, although cardiovascular disease incidence rates vary substantially by country of origin. The "healthy immigrant effect" is the hypothesis that immigrants to high-income countries, such as Canada, are healthier than nonimmigrants in the host population. However, this effect may not apply universally across all immigrants, including recent refugees, immigrants without formal education, and unmarried immigrants. As unfolding sociopolitical events generate new waves of global migration, policymakers and health care providers need to focus on addressing social and structural determinants of health to better manage cardiovascular risk factors and prevent cardiovascular disease, especially among the most marginalized immigrants and refugees.

Proportion of Life Spent in Canada and the Incidence of Multiple Sclerosis in Permanent Immigrants

BACKGROUND AND OBJECTIVES

While immigrants to high-income countries have a lower risk of multiple sclerosis (MS) compared with host populations, it is unknown whether this lower risk among immigrants increases over time. Our objective was to evaluate the association between proportion of life spent in Canada and the hazard of incident MS in Canadian immigrants.

METHODS

We conducted a population-based retrospective cohort study in Ontario, using linked health administrative databases. We followed immigrants, who arrived in Ontario between 1985 and 2003, from January 1, 2003, to December 31, 2016, to record incident MS using a validated algorithm based on hospital admission or outpatient visits. We derived proportion of life spent in Canada based on age at arrival and time since immigration obtained from linked immigration records. We used multivariable proportional hazard models, adjusting for demographics and comorbidities, to evaluate the association between proportion of life in Canada and the incidence of MS, where proportion of life was modelled using restricted cubic spline terms. We further evaluated the role of age at migration (15 or younger vs older than 15 years), sex, and immigration class in sensitivity analyses.

RESULTS

We included 1.5 million immigrants (49.9% female, mean age 35.9 [SD 14.2] years) who had spent a median of 20% (Q1-Q3 10%-30%) of their life in Canada. During a mean follow-up of 13.9 years (SD 1.0), 934 (0.44/100,000 person-years) were diagnosed with MS. Compared with the median, a higher risk of MS was observed at higher values of proportion of life spent (e.g., hazard ratio [70% vs 20% proportion of life] 1.38; 1.07-1.78). This association did not vary by sex (p(sex × proportion of life) = 0.70) or immigration class (p(immigration class × proportion of life) = 0.13). The results did not vary by age at migration but were statistically significant only at higher values of proportion of life for immigrants aged 15 years or younger at arrival.

DISCUSSION

The risk of incident MS in immigrants varied with the proportion of life spent in Canada, suggesting an acculturation effect on MS risk. Further work is required to understand environmental and sociocultural factors driving the observed association.

A Systematic Review and Meta-Analysis of the Associations between Immigration Status and Stroke Incidence and Mortality

Methods

We thoroughly searched PubMed, Embase, and MEDLINE databases for the literature on stroke risk for immigrants and host populations by January 2022. Fourteen relevant cohort studies from eight countries met the inclusion criteria, and their data were included in this meta-analysis. Heterogeneity and publication bias were assessed.

Results

The results showed that the immigrant groups suffered from a lower incidence rate of stroke compared with the host populations (HR = 0.81, 95% CI 0.71-0.91, P = 0.001), but there was nonsignificant higher mortality of stroke in immigrants (HR = 1.07; 95% CI 0.84-1.36). However, the pooled adjusted incidence HR reduced to 0.67 (95% CI 0.60-0.75) after adjustment for publication bias. Immigrants had a lower stroke incidence compared to long-term residents, but the association varied with the country of origin, socioeconomic status, residence (urban vs. rural), and comorbid conditions. Discussion. The present systematic review and meta-analysis implicated that stroke risks are different for immigrants and the host populations; therefore, this knowledge may be useful for developing targeted stroke prevention strategies.