Spotlight on ethnic differences in diabetes

Two recent studies highlighted some differences among ethnic groups in risk and incidence of diabetes.

In the first study, published by Diabetic Medicine on Oct. 1, British researchers measured body mass index (BMI) and performed fasting and glucose tolerance tests on people between 40 and 69 years of age in 1988 to 1991. The study included 1,356 patients of European origin, 842 first-generation immigrants from South Asia, and 335 African-Caribbean immigrants. They were followed for up to 19 years through their primary care records. The rate of diabetes incidence was higher in South Asians (20.8 per 1,000 person-years in men, 12.0 per 1,000 person-years in women) and African-Caribbeans (16.5 per 1,000 person-years in men, 17.5 per 1,000 person-years in women) than Europeans (7.4 per 1,000 person-years in men, 7.2 per 1,000 person-years in women). Researchers calculated that an equivalent increase in diabetes risk was seen at a BMI of 25.2 kg/m² in South Asians and 27.2 kg/m² in African-Caribbeans as a BMI of 30 kg/m² in Europeans. Waist circumference cutpoints for elevated diabetes risk would also be lower: 90.4 cm in South Asian men and 90.6 cm in African-Caribbean men would be equivalent to 102 cm in European men, and 84.0 cm in South Asian women and 81.2 cm in African-Caribbean women would be equivalent to 88 cm in European women. These are “striking ethnic differences in diabetes incidence,” the researchers concluded. The findings could be used to target health behavior interventions, such as encouragement of physical activity, toward these at-risk groups. However, the lowered cutpoints should not be used to expand the definition of obesity in certain ethnic groups, because of possible unintended consequences, they said.

In the other study, published in the Sept. 24 Journal of the American Medical Association, data from the CDC's National Health Interview Survey were used to track the prevalence and incidence of diabetes in more than 600,000 adults ages 20 to 79 between 1980 and 2012. The study found the age-adjusted prevalence and incidence of diabetes was stable during the 1980s, doubled between 1990 and 2008, and then leveled off with no significant change between 2008 and 2012. However, incidence rates for non-Hispanic blacks and Hispanics continued to increase even after the overall rate leveled off (P= 0.03 for blacks and 0.01 for Hispanics compared with incidence rate in whites). Diabetes also increased faster in those with a high school education or less. The variation in rates among these subgroups “threatens to exacerbate racial/ethnic and socioeconomic disparities in diabetes prevalence and incidence,” the study authors said. They note the 1997 change in the diagnostic criteria for diabetes could have contributed to the increased incidence, but since their study found incidence began to increase in 1990 and there were no dramatic shifts after 1997, the diagnostic change is unlikely to explain the observed increase. The authors conclude that their results lend support to other population-based studies finding that adiposity is significant factor in the increasing incidence of diabetes.