Racial/ethnic differences in the burden of type 2 diabetes over the life course: a focus on the USA and India

Abstract

Type 2 diabetes is a common disease worldwide, but its prevalence varies widely by geographical region and by race/ethnicity. This review summarises differences in the frequencies of type 2 diabetes according to race, ethnicity, socioeconomic position, area of residence and environmental toxins. Type 2 diabetes susceptibility often begins early in life, starting with genetic susceptibility at conception and continuing in later life, via in utero, childhood and adult exposures. Early-life factors may lead to overt type 2 diabetes in childhood or in later life, supporting the concept of developmental origins of health and disease. The causes of the racial/ethnic differences in incidence of type 2 diabetes are not well understood. Specifically, the relative contributions of genetic and environmental factors to such differences are largely unknown. With a few exceptions in isolated populations, there is little evidence that differences in frequencies of known type 2 diabetes susceptibility genetic alleles account for racial/ethnic differences, although the search for genetic susceptibility has not been uniform among the world's racial/ethnic groups. In the USA, race/ethnicity is associated with many other risk factors for type 2 diabetes, including being overweight/obese, diet and socioeconomic status. Some studies suggest that some of these factors may account for the race/ethnic differences in prevalence of type 2 diabetes, although there is inadequate research in this area. A better understanding of the impact of these factors on type 2 diabetes risk should lead to more effective prevention and treatment of this disease. This has not yet been achieved but should be a goal for future research.

Keywords: Life course development; Race/ethnicity; Review; Type 2 diabetes mellitus.

Fig. 1

Age-specific prevalence of diagnosed diabetes in the USA by race/ethnicity. Data from the NHIS, 2011–2015, reported in [1]. AI/AN, American Indian/Alaska Native; NHB, non-Hispanic black; NHW, non-Hispanic white. This figure is available as part of a downloadable slideset

Fig. 2

Cumulative distribution of genetic risk score for type 2 diabetes, calculated by summing the number of risk alleles weighted by the published effect size across 63 established variants, in different racial/ethnic groups. American Indians were Pima Indians who participated in a longitudinal study; the other populations were derived from the International HapMap project and included Han Chinese individuals from Beijing (East Asians), Centre d’Etude du Polymorhisme Humain families from Utah (Europeans) and Yoruba people from Ibadan Nigeria (Africans). A rightward shift of the curve is suggestive of a higher genetic risk for type 2 diabetes. Adapted from [23]. This figure is available as part of a downloadable slideset

Fig. 3

Incidence of diagnosed type 2 diabetes in youth (aged 10–19 years) in the USA by race/ethnicity according to the SEARCH study. This figure was created using data in Table 2 of reference [51]. AI/AN, American Indian/Alaska Native; NHB, non-Hispanic black; NHW, non-Hispanic white. This figure is available as part of a downloadable slideset

Fig. 4

Infants of mothers with diabetes, at least in high-risk populations such as American Indians, are at high risk of developing diabetes as children and young adults. By the time they become pregnant, these female offspring may already have diabetes and, thus, perpetuate this vicious cycle. Adapted from [48], with permission from John Wiley and Sons. This figure is available as part of a downloadable slideset