Higher risk of gastric cancer among immigrants to Ontario: a population-based matched cohort study with over 2 million individuals
The risk of gastric carcinoma (GC) varies around the world and between females and males. We aimed to compare the risk of GC among immigrants to Ontario, Canada, to the risk of GC in its general population.
This was a retrospective population-based matched cohort study from 1991 to 2014. We identified immigrants who were first eligible for the Ontario Health Insurance Plan at age 40 years or older, and matched 5 controls by year of birth and sex. We calculated crude rates and relative rates of GC stratified by sex. We modeled GC hazard using multivariable Cox proportional hazards regression, where a time-varying coefficient was incorporated to examine changes in the association of immigrant status with GC hazard over time.
Among females, 415 GC cases were identified among 209,843 immigrants and 1872 among 1,049,215 controls. Among males, 596 GC cases were identified among 191,792 immigrants and 2998 among 958,960 controls. Comparing immigrants from East Asia and Pacific with the controls, the crude relative rate of GC was 1.54 for females and 1.32 for males. The adjusted hazard ratio (HR) for GC among female immigrants was 1.29 [95% confidence interval (CI) 1.12, 1.48] within 10 years and 1.19 (1.01, 1.40) beyond 10 years; for males, the HR was 1.17 (1.04, 1.31) within 10 years and 1.00 (0.87, 1.15) beyond 10 years.
The risk of GC among immigrants is elevated. Although high-risk immigrant populations in Ontario have been identified, further knowledge is required before a program of GC prevention that is targeted to them can be planned.
KeywordsImmigrants Matched cohort study Gastric cancer Cox regression model with time-varying coefficient Relative rate
This study was conducted with the support of Cancer Care Ontario through funding provided by the Government of Ontario. It was supported by the Institute for Clinical Evaluative Sciences (ICES), which is funded by an annual grant from the Ontario Ministry of Health and Long-Term Care (MOHLTC). The opinions, results, and conclusions reported in this paper are those of the authors and are independent from the funding sources. Parts of this material are based on data and information provided by Cancer Care Ontario (CCO). The opinions, results, views, and conclusions reported in this paper are those of the authors and do not necessarily reflect those of CCO. No endorsement by ICES or the MOHLTC or CCO is intended or should be inferred.
Author contribution statement
All of the authors had roles in the design and conduct of the study. RS, NA, and FL planned and executed the statistical analyses. All of the authors had roles in the interpretation of the results, as well as the preparation and approval of the article.
Compliance with ethical standards
Conflict of interest
We declare that we have no conflict of interest.
This study was approved by the Sunnybrook Health Sciences Centre Research Ethics Board.
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