National study examines relationship between immigration status and the prevalence of non-food allergies

A study published in the Canadian Journal of Public Health has found that immigrants to Canada have fewer non-food allergies than the non-immigrant population, but that the difference diminishes with longer duration of residence in Canada.

The study, which is based on data collected from 116,232 respondents from the Canadian Community Health Survey, represents approximately 98% of the Canadian population. It examined the prevalence of non-food allergies, such as allergic rhinitis and other respiratory allergies, among recent immigrants (immigrated to Canada within the last 10 years), long-time immigrants (immigrated to Canada more than 10 years ago) and non-immigrants.

Among immigrants who had lived in Canada for fewer than 10 years, only 14.3% had non-food allergies, while the rates for immigrants resident in Canada over 10 years and for non-immigrants were 23.9% and 29.6% respectively.

“This finding supports the ‘healthy immigrant effect’ theory, which states that new Canadians tend to have a low prevalence of chronic conditions, but their health status worsens with time and eventually converges with that of the Canadian-born population,” says Dr. Hind Sbihi, an AllerGen Highly Qualified Personnel from The University of British Columbia (UBC) who led the research. Jiayun Yao, a PhD candidate at UBC’s School of Population and Public Health, was a co-author.

The lower prevalence of allergies among recent immigrants compared with non-immigrants may be partly attributed to differences in genetic and environmental risk factors for allergies between their countries of origin and Canada, according to the researchers. In contrast, the increased prevalence among long-time immigrants compared with recent immigrants primarily reflects the impact of environmental risk factors, such as urban living, lifestyle and diet.

“This may indicate that the immune systems immigrants developed during their early life in their countries of origin, which were protective against allergies, can be reprogrammed to develop allergies later in life when adapting to the new environment,” comments Sbihi.

She adds that while food allergies have received substantial attention from the public, the media, and the research community, it is also important to create awareness for allergies that result from other routes of exposure, such as inhalation.

The study’s findings will help researchers to better understand the impact of environmental determinants of allergy development and may help to inform the design of multicultural strategies to manage the public health burden of allergic conditions.