Patterns of tuberculosis risk over time among recent immigrants to Ontario, Canada.

SETTING

Canada receives more than 200000 immigrants annually. Immigrants account for 92% of tuberculosis (TB) cases in Toronto, Ontario. Epidemiological profiling of recent immigrants is needed to provide more effective TB programs.

DESIGN

A population-based, retrospective cohort study of recent immigrants to Ontario, 1990-1997. We generated adjusted rates, risk ratios (RRs), hazard rates since arrival, and a complementary log-log model to describe TB risk, compare the survival distributions between different sexes, age groups and world regions of birth, and determine predictors of disease.

RESULTS

TB in recent immigrants was 23 times (95%CI 20.9-25.5) higher than in Canadian-born, non-aboriginal people. Those aged 16-30 and >65 years experienced the highest rates. Sub-Saharan Africa had the highest rates for both sexes (RR 95.5, 95%CI 84.3-108.2), followed by India and Asia. Hazard rates decreased after arrival, but remained elevated. The highest risk was associated with arrival in 1990 and living in Canada <1 year.

CONCLUSION

Risk for TB varied by region of birth, age at landing and time since arrival. Sex was not significant. Persons from sub-Saharan Africa and age >65 years were the highest risk groups. Risk decreased significantly in the first 1-2 years after arrival, after which it plateaued.