Language proficiency and warfarin-related adverse events in older immigrants and Canadian residents: a population-based cohort study

Introduction Language proficiency may influence safe medicine use among new immigrants and contribute to adverse drug events and healthcare utilization. Methods A retrospective cohort study was conducted to investigate the effects of immigration status and self-reported language proficiency on unplanned healthcare visits. Each new immigrant (language proficient [LP] and non-language proficient [non-LP] immigrants) was matched 1:2 with longstanding Canadian residents. Outcomes while receiving warfarin therapy included unplanned hospital visits for any cause and for bleeding within 180 days of cohort entry (first prescription for warfarin after age 66 years). Results A total of 906 immigrants (446 LP, 460 non-LP) were matched to 1812 longstanding Canadian residents. Immigrants were less likely than longstanding Canadian residents to have unplanned hospital visits during warfarin therapy (hazard ratio [HR] 0.74; 95% confidence interval [CI] 0.63-0.88). Immigrants who were non-LP were less likely than LP immigrants to present to hospital for any cause (HR 0.77; 95% CI 0.60-0.99). No significant differences in hospital visits for bleeding events were found between groups. Discussion Immigrants were less likely than longstanding Canadian residents to have unplanned hospital visits. Among immigrants, those who were non-LP were less likely than those who were LP to have unplanned healthcare visits. However, unplanned healthcare visits related to bleeding were similar between groups. Several sociocultural factors and differing structural barriers may help to explain the observed differences in hospital visit rates. Failure to identify differences in bleeding events may relate to factors that preserve adherence to warfarin despite limited language proficiency.