Population-based differences in cancer incidence between immigrants and non-immigrants in Canada between 1992 and...

With increasing immigration in Canada and strained cancer treatment infrastructure, there's a pressing need for long-term data on immigrant health and cancer incidence. This information is crucial for planning future cancer services and to alleviate the burden on both the population and healthcare system.

Statistics Canada data were linked from the 1991 Canadian Census, Canadian Cancer Registry, and Canadian Vital Statistics Database to follow a cohort from 1992 to 2015 and compare cancer incidence between immigrants and the Canadian-born for any cancer and specific types of cancers. Immigrants were further classified based on time spent in Canada.

Immigrants had lower odds of developing any cancer (OR = 0.92, 95% CI [0.92-0.93], p < 0.001) compared to non-immigrants. However, for stomach cancer and non-cervical gynecological cancers, the odds of cancer incidence were greater for immigrants than for the Canadian-born. Cox regression showed that recent immigrants (0-4 years in Canada) had a lower hazard ratio (HR = 0.77, 95% CI [0.71-0.84], p < 0.001) compared to non-immigrants. Those who lived 5-9 years and 10-19 years in Canada had a higher hazard ratio (HR = 0.82, 95% CI [0.75-0.89], p < 0.001; HR = 0.90, 95% CI [0.82-0.98], p = 0.011), respectively. Immigrants who had been in Canada for 20 years or longer had the highest hazard ratio (HR = 0.98, 95% CI [0.90-1.07], p = 0.632), indicating that the so-called "healthy immigrant effect" lessens over time.

Results demonstrated the healthy immigrant effect lessens over time spent in Canada. However, this effect was not uniform across countries of origin and cancer types. Therefore, this research, provides a deeper understanding of immigrant cancer outcomes and will be useful for cancer planning services and cancer control strategies.