Neighbourhood immigrant concentration and hospitalization: a multilevel analysis of cardiovascular-related admissions in Ontario using linked data.

OBJECTIVE To assess the influence of neighbourhood immigrant concentration on cardiovascular-disease-related hospitalizations in Canada (CVDH), while adjusting for individual-level immigrant status and socio-economic indicators at individual and neighbourhood levels. METHODS Data were from the 2006 Canadian Census linked to the hospital Discharge Abstract Data (DAD) for the province of Ontario. Adults (n=1,459,950) aged ≥18 years at baseline and grouped by place of birth (Canada, China, South Asia, Europe, and other) were followed between Census Day May 16, 2006 and March 31, 2008. Information on CVDH was obtained from the DAD, while that on immigration and socio-economic indicators was obtained from the Census. The analysis used multilevel logistic regression. RESULTS Unadjusted results showed that CVDH was significantly lower among people living in neighbourhoods with medium and high immigrant concentration. Neighbourhood immigrant concentration tended to have no independent effect on CVDH after adjustment for individual-level immigrant status. Immigrants were less likely to experience CVDH irrespective of their country of birth. However, cross-level interaction showed that neighbourhood immigrant concentration provided additional protection to individual-level immigrant status against CVDH for most female immigrant groups, but only for South Asian males. CONCLUSION This study resulted from the first-ever linkage of census data to hospitalization data in Canada. It is also the first Canadian study to report on neighbourhood variation and the effect of immigrant concentration on CVDH. The study shows that understanding immigrant health requires both individual and neighbourhood approaches, and a consideration of country of origin.