Risk of Developing Multimorbidity among Previously Healthy Immigrants and Long-term Ontario Residents

Background Multimorbidity is an important health issue associated with a greater risk of adverse health outcomes, more frequent hospitalizations, greater healthcare needs, and premature death. This study examined patterns of and the risk of developing multimorbidity between immigrants and long-term residents of Ontario. Methods We used a 1:1 matched retrospective observational open cohort design from 1995 to 2016, using routinely collected population-based administrative data at ICES. Multimorbidity was defined as two or more and three or more co-occurring chronic conditions. Chronic disease frequencies of dyads and triads were examined. Stratified multivariate Cox Proportional Hazard models examined the risk of developing multimorbidity and further by world regions of origin for immigrants compared to long-term residents. Results Hypertension and diabetes, in combination with chronic obstructive pulmonary disease, were the leading multimorbidity dyad and triad groups. After controlling for age, sex, and neighborhood income quintiles, immigrants from the Caribbean and South Asia had a greater risk of developing 2+ multimorbidity, compared to long-term residents. Refugees from North Africa and the Middle East (HR = 1.22 [95% CI: 1.03-1.42]) as well as refugees (HR = 1.78 [95% CI: 1.59 – 1.98]) and family immigrants from South Asia (HR: 1.08 [95% CI: 1.02-1.14]), had a higher risk of 3+ multimorbidity compared to long-term residents of Ontario. Conclusion These findings highlight the importance of routine population-based data collection on immigration status and world regions of origin to inform public health research. Investments in preventive health services and management of multimorbidity are needed for specific population groups.