Proportion of life spent in Canada and stroke incidence and outcomes in immigrants

Background — To evaluate the association between proportion of life spent in a host nation and stroke incidence and outcomes among Canadian immigrants.

Methods — We conducted a retrospective cohort study of 1.2 million adult Canadian immigrants (mean age 40 [±14.6] years, 50.5% women) who were followed between 2003 and 2018 using linked administrative health data. Using multivariable cause-specific hazard models, we evaluated the overall and sex-specific associations between the proportion of life spent in Canada (φ), modelled as restricted cubic splines, and ischemic stroke incidence and outcomes.

Results — Compared to the median proportion of life in Canada (φ = 0.2), a J-shaped association between proportion of life in Canada and ischemic stroke incidence and outcomes was observed. The adjusted hazard ratios of stroke incidence increased with both progressively lower and higher levels of φ [e.g., (HRφ=0.05 vs. φ=0.20, 1.15; 1.09-1.21) and (HRφ=0.50 vs. φ=0.20, 1.45; 1.27-1.66)]. In sex-stratified analyses, the associations between φ and stroke incidence and outcomes were significant in men, but not in women.

Conclusions — Stroke incidence and outcomes among immigrants varies with the proportion of life spent in Canada. Future work should identify factors driving the observed associations and the sex-differences.