Incident Kidney Disease in Canadian Immigrants vs. Non-Immigrants

Abstract

Chronic kidney disease is a widespread public health concern that is largely affected by social determinants of health. Social determinants of health are non-medical factors that play a role in the health of an individual. An under-explored social determinant of health in relation to kidney disease is immigrant status. A "healthy immigrant effect", whereby immigrants experience a health advantage compared to non-immigrants, has previously been reported in relation to other health conditions such as heart disease and diabetes but has never been studied in regard to kidney disease. The link between immigrant status and the development of kidney disease remains poorly understood. On one hand, immigrant populations are often negatively affected by social factors such as poverty, food insecurity, and housing instability, all of which have been linked to worse kidney health outcomes. However, on the other hand, a "healthy immigrant effect", referring to a reduced prevalence of age-related disease among immigrants compared to their non-immigrant counterparts, has previously been demonstrated with other chronic diseases such as cardiovascular disease, diabetes, and dementia. To better understand the association between immigrant status and kidney disease, we herein conducted a population-based cohort study to compare the incidence of early-stage CKD among immigrants versus non-immigrants in Ontario, Canada.

We begin by taking a look at the burden of kidney disease, how it is measured, and how it is viewed in the context of immigrant status. Next we conducted a population-level, observational cohort study of all adult (≥18 years of age) Ontario residents, including foreign-born immigrant Canadian citizens and non-immigrant Canadian citizens by birth, with normal baseline kidney function (outpatient estimated glomerular filtration rate [eGFR] ≥70 mL/min/1.73m²) between April 1, 2007 and September 30, 2020 utilizing provincial health administrative data from ICES. Utilizing this data we had two main objectives:

1) To determine the incidence of early-stage chronic kidney disease, defined by an estimated glomerular filtration rate (eGFR) measurement less than or equal to 60 mL/min/1.73m², in Canadian Immigrants compared to their non-immigrant counterparts.

2) To examine the association of more severe forms of kidney disease; a 40% reduction in eGFR or kidney failure, in Canadian immigrants vs. non-immigrants.

Within both objective one and two we also examine how refuges status, landing date and world-region of origin influence the association the association between immigrant status and incident CKD.

In study 1 we found that there was about a 20% reduction (adjusted HR 0.80 [95% CI 0.80-0.81]) in incident CKD risk in immigrants vs. non-immigrants after adjusting for confounders. In study 2 we found that there was about a 30% reduction (adjusted HR 0.70 [95% CI 0.69-0.71]) in composite end-stage kidney disease outcome risk in Canadian immigrants vs. non-immigrants. These trends persisted through sensitivity analyses. Additionally, both recent and remote immigrants had reduced CKD risk compared to non-immigrants in study 1 and 2.