A population-based cohort study defined estimated glomerular filtration rate decline and kidney failure among Canadian immigrants

The link between immigrant status, a key social determinant of health, and kidney disease remains uncertain. To evaluate this, we compared incident adverse kidney outcomes between immigrants and non-immigrants using Canadian provincial health administrative data. We conducted a population-based observational cohort study of all adult Ontario residents (immigrants and non-immigrants) with normal baseline kidney function (estimated glomerular filtration rate (eGFR) 70 mL/min/1.73m² or more). Multivariable Cox proportional hazard regression modeling was used to evaluate the relationship between immigrant status and the composite adverse kidney outcome of 40% eGFR decline or kidney failure. The study cohort included 10,440,210 individuals with 22% immigrants and 78% non-immigrants. The mean (Standard Deviation) age and eGFR were 45 (17) years and 102 (16) mL/min/1.73m², respectively. Immigrants experienced a 27% lower hazard for the composite adverse kidney outcome (adjusted hazard ratio 0.73 [95% Confidence Interval 0.72-0.74]) compared to non-immigrants which was primarily driven by 40% eGFR decline. However, immigrants also experienced a 12% lower hazard for incident kidney failure (0.88 [0.84-0.93]) compared to non-immigrants. Results were consistent upon accounting for the competing risk of death and adjusting for baseline albuminuria. As has been demonstrated with other chronic diseases, these novel findings suggest that a "healthy immigrant effect" also extends to kidney disease. Differential kidney disease outcomes were identified among immigrants based on refugee status and world region of origin which may inform health policy decision-making toward targeted screening strategies and more cost-effective resource allocation for immigrant populations.