Higher risk of gastric cancer among immigrants to Ontario: a population-based matched cohort study with over 2 million individuals

Background — 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.

Methods — 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.

Results — 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.

Conclusion — 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.