These data support the following three main conclusions. First, although Asian Americans were more likely to attend college, were less likely to smoke, were less likely to drink, and had lower BMI, Asian Americans are ~30% more likely to have type 2 diabetes than their white counterparts. Second, both BMI and diabetes prevalence are rising in all Asian subgroups, especially Filipinos. Third, although the OR of diabetes in Asians versus whites has remained relatively stable over the past decade, the steady climb in diabetes prevalence in both groups coincides with a widening gap in terms of absolute diabetes prevalence. We noted that compared with whites, Asian Americans were more likely to be overweight but less likely to be obese, after applying the modified Asian criteria. Nonetheless, we should interpret the observation with caution because the real overweight/obesity cut points are likely to vary for different Asian populations (11
Our results are consistent with previous studies of diabetes in Asian Americans. Using 3-year (2004–2006) pooled NHIS data, Barnes et al. (5
) reported an age-standardized diabetes prevalence of 7.5% in whites versus 6.4% in Asian Americans. In a study using the 2001 U.S. Behavioral Risk Factor Surveillance System data, McNeely and Boyko (6
) found that type 2 diabetes was 60% more likely in Asian Americans than in whites (OR 1.6 [95% CI 1.1–2.2]). Most recently, two studies used NHIS data to compare the risk of type 2 diabetes in subgroups of Asians (i.e., Chinese, Filipinos, Asian Indians, and other Asians) to whites. Oza-Frank et al. (12
) showed that the risk in Asians was higher than whites across all Asian subgroups (OR range 1.3–3.5). Ye et al. (13
) likewise observed that Asian Indians and Filipinos were more likely to have type 2 diabetes than whites (OR range 1.1–2.3) after multiple adjustment. In this study, we further investigated trends in diabetes prevalence over time and in relation to patterns of change in BMI. We found that although the ORs of diabetes in Asians versus whites has remained quite stable over the past decade, obesity and diabetes prevalence in both race groups increased concurrently. Those increases contribute to the growing medical and societal burdens in the U.S. attributed to diabetes and its complications.
There are several possible explanations for the Asian–white disparity in diabetes risk. First, Asians appear to be more genetically predisposed to develop type 2 diabetes compared with their white counterparts (14
). Second, chronic stress related to immigration acculturation could contribute to visceral adiposity and insulin resistance (16
). Finally, Asians are known to have higher visceral fat accumulation compared with whites at any given level of BMI (17
). Rush et al. (18
) reported that for the same BMI, the body fat percentage in Asian Indians was higher than whites as well as other Asian populations. Likewise, for the same waist circumference, Filipino women had a higher visceral fat and visceral-to-subcutaneous abdominal fat ratio than white women (19
). Those unfavorable fat distributions may contribute to the higher risk of diabetes in those two Asian populations (9
Physical inactivity is a well-established risk factor for incident type 2 diabetes independent from adiposity (20
). Although physical inactivity did not completely explain the excess risk of type 2 diabetes in Asian Americans in our analysis, it is known to be a common diabetes risk factor in Asian Americans. For example, Kandula et al. (21
) observed that Asian immigrants were 50% less likely to meet the recommended physical activity level than U.S.-born non-Asians, based on the 2001 California Health Interview Survey. Physical inactivity is of particular interest from a public health perspective because it is more readily modifiable than adiposity.
Strengths of our study include a very large, nationally representative sample with uniform ascertainment of diabetes and related variables over a time interval during which the population of Asian Americans and the prevalence of type 2 diabetes have both climbed dramatically.
Nevertheless, several limitations deserve mention. First, the secular patterns we observed were based entirely on cross-sectional data; therefore, these results may have been influenced by survival and/or selection bias related to immigration that limited the inferences about racial disparities in incident diabetes risk. Second, the NHIS is based exclusively on self-reported data. Because participants were asked to select a primary race, possible misclassification in mixed-race participants may underestimate the associations. It is also possible that the disparities we observed arose in part from racial differences in physician diagnosis and/or patient recall of diabetes. Use of self-reported height and weight may lead to underestimation of BMI, but we know of no evidence that the degree of underestimation differs systematically in Asian Americans versus whites (22
). Finally, information on other diabetes risk factors, such as dietary intake and family history of diabetes, are not available in the NHIS. Hence, we could not rule out the possibility of residual confounding.
The main implication of our study is that type 2 diabetes is a growing public health problem for Asian Americans that requires urgent attention. Although greater genetic predisposition no doubt plays a role, future research should identify modifiable risk factors that underlie the Asian–white disparity in diabetes prevalence as a step toward the development of culturally tailored prevention strategies.