Tuberculosis incidence among migrants according to migrant status: a cohort study, Denmark, 1993 to 2015

Background: Migrants account for the majority of tuberculosis (TB) cases in low-incidence countries in western Europe. TB incidence among migrants might be influenced by patterns of migration, but this is not well understood. Aim: To investigate differences in TB risk across migrant groups according to migrant status and region of origin. Methods: This prospective cohort study included migrants >= 18 years of age who obtained residency in Denmark between 1 January 1993 and 31 December 2015, matched 1:6 to Danish-born individuals. Migrants were grouped according to legal status of residency and region of origin. Incidence rates (IR) and incidence rate ratios (IRR) were estimated by Poisson regression. Results: The cohort included 142,314 migrants. Migrants had significantly higher TB incidence (IR: 120/100,000 person-years (PY); 95% confidence interval (CI): 115-126) than Danish-born individuals (IR: 4/100,000 PY; 95% CI: 3-4). The IRR was significantly higher in all migrant groups compared with Danish-born (p < 0.01). A particularly higher risk was seen among family-reunified to refugees (IRR: 61.8; 95% CI: 52.7-72.4), quota refugees (IRR: 46.0; 95% CI: 36.6-57.6) and former asylum seekers (IRR: 45.3; 95% CI: 40.2-51.1), whereas lower risk was seen among family-reunified to Danish/Nordic citizens (IRR 15.8; 95% CI: 13.6-18.4) and family-reunified to immigrants (IRR: 16.9; 95% CI: 13.5-21.3). Discussion: All migrants had higher TB risk compared with the Danish-born population. While screening programmes focus mostly on asylum seekers, other migrant groups with high risk of TB are missed. Awareness of TB risk in all high-risk groups should be strengthened and screening programmes should be optimised.