Diabetes screening among immigrants: a population-based urban cohort study

OBJECTIVE

To examine diabetes screening, predictors of screening, and the burden of undiagnosed diabetes in the immigrant population and whether these estimates differ by ethnicity.

RESEARCH DESIGN AND METHODS

A population-based retrospective cohort linking administrative health data to immigration files was used to follow the entire diabetes-free population aged 40 years and up in Ontario, Canada (N = 3,484,222) for 3 years (2004–2007) to determine whether individuals were screened for diabetes. Multivariate regression was used to determine predictors of having a diabetes test.

RESULTS

Screening rates were slightly higher in the immigrant versus the general population (76.0 and 74.4%, respectively; P < 0.001), with the highest rates in people born in South Asia, Mexico, Latin America, and the Caribbean. Immigrant seniors (age ≥65 years) were screened less than nonimmigrant seniors. Percent yield of new diabetes subjects among those screened was high for certain countries of birth (South Asia, 13.0%; Mexico and Latin America, 12.1%; Caribbean, 9.5%) and low among others (Europe, Central Asia, U.S., 5.1–5.2%). The number of physician visits was the single most important predictor of screening, and many high-risk ethnic groups required numerous visits before a test was administered. The proportion of diabetes that remained undiagnosed was estimated to be 9.7% in the general population and 9.0% in immigrants.

CONCLUSIONS

Overall diabetes-screening rates are high in Canada’s universal health care setting, including among high-risk ethnic groups. Despite this finding, disparities in screening rates between immigrant subgroups persist and multiple physician visits are often required to achieve recommended screening levels.Diabetes is a serious chronic disease that is associated with substantial increases in morbidity and mortality and imposes a huge economic burden on society. Although screening for diabetes is increasing in Canada (1), up to one-third of all diabetes subjects are thought to be undiagnosed in the general population in Canada and the U.S., an estimate that may now be out of date (2,3). One significant factor that is likely contributing to increased screening is the rising prevalence of obesity in the population.Early detection and control of diabetes can potentially reduce the heightened risk of cardiovascular morbidity and mortality associated with this disease. People with screen-detected diabetes have an increased risk of heart disease as compared with the general population, and this risk is modifiable with treatment (4–6). In addition, timely screening can prevent the onset of common diabetes-related complications that could be avoided through early detection and treatment (e.g., retinopathy, peripheral neuropathy, and peripheral vascular disease) (7).National guidelines in both the U.S. and Canada recommend that diabetes screening should be performed on those aged 45 years (U.S.) or 40 (Canada) years and over every 3 years, with more frequent or earlier screening for those with additional risk factors, including belonging to a high-risk ethnic group (8,9). Ethnic groups that have been shown to display an elevated risk for diabetes include people of South Asian (10–12), Aboriginal (13), and African-Caribbean descent (2,11). Many of the 250,000 immigrants to Canada every year (14) belong to ethnicities that experience higher rates of diabetes (11) and who therefore should be screened regularly and beginning at a younger age. There is evidence, however, that immigrants may have lower health care utilization (15), which may predispose this group to have lower rates of screening than the Canadian-born population. An important and currently unanswered question, therefore, is whether some ethnic or migrant groups are more likely to be underdiagnosed than others. In this study, we describe the pattern of diabetes screening among recent immigrants to Ontario by looking at screening rates, screening efficiency/yield, predictors of screening, and the burden of undiagnosed diabetes in this population by region of origin.