Of 64,211 diabetic patients, ~63% were white, 13% were African American, 12% were Latino, 6% were Filipino, 3% were Chinese, 1% were Japanese, 1% were Pacific Islanders, and 1% were South Asians. There were a total of 6,901 (11%) Asian participants in aggregate and an additional 593 (1%) Pacific Islanders included in this analysis. The total follow-up time was ~413,500 person-years or a mean of 7.2 ± 3.3 years from 1996 to 2006.
Each of the eight ethnic groups were ~50% women, except for the Chinese (42% women) and South Asian (30% women) groups (). Mean age differed somewhat by ethnicity, with Japanese respondents being oldest (aged 62 ± 11 years) and South Asians being the youngest (aged 53 ± 11 years). College graduation rates were highest among South Asians (55%), Filipino (47%), Chinese (37%), and Japanese (33%) and lowest among Pacific Islanders (14%) and Latinos (12%). There were high proportions of African Americans (47%) and Latinos (31%) living in the most deprived neighborhoods. Chinese Americans (33%) were most likely to have limited English proficiency. The average BMI was similar for whites, African Americans, Latinos, and Pacific Islanders (~30 ± 6 kg/m2 for each) and lower for the other four Asian subgroups (mean 25–26 kg/m2 per group). The prevalence of smoking was highest among African Americans (16%) and Pacific Islanders (14%) and lowest among the Chinese and South Asian (≤5%) groups. The mean duration of diagnosed diabetes was similar for whites, African Americans, Latinos, and Japanese (10 ± 10 years for each group) but lower for Chinese (9 ± 11 years), Filipinos (8 ± 8 years), Pacific Islanders (8 ± 9 years), and South Asians (8 ± 7 years). More than half of all participants in each ethnic group were using oral hypoglycemic medications for diabetes treatment, had a family history of diabetes, and had hypertension.
Baseline characteristics of 64,211 participants with diabetes by race/ethnic group*
We calculated the crude and age- and sex-adjusted incidence rates per ethnic group for each of the five diabetes complications (). We also show the aggregated rates of the four Asian subgroups together for comparison with the individual Asian subgroups. The fully adjusted rate ratios comparing each ethnic group to whites are displayed. The table shows the HR (95% CI) for each ethnic group compared with whites for each of the diabetes complications.
Crude age- and sex-adjusted incidence rates and fully adjusted rate ratios* of each outcome by racial subgroup, DISTANCE study, 1996–2006
There were a total of 6,088 people with incident MI during the follow-up period. The aggregated Asian incidence rate (10.8 [95% CI 9.9–11.8]) completely obscured the wide range of rates across the four Asian subgroups. The highest incidence of MI occurred in Pacific Islanders (18.5 [14.3–23.5] per 1,000 person-years), and the lowest incidence was in Chinese (9.2 [7.7–11.0] per 1,000 person-years). After age and sex adjustment, the rates were attenuated, but Pacific Islanders had the highest incidence of MI (10.1 per 1,000 person-years) of all groups, whereas Japanese (3.3 per 1,000 person-years) had the lowest incidence of MI, with whites in the middle of this range (5.9 per 1,000 person-years). These differences between subgroups persisted despite multivariate adjustment for several potentially explanatory factors (). In fully adjusted models, compared with whites, most racial/ethnic groups had significantly lower hazards of MI. However, Pacific Islanders had significantly higher risk (HR 1.29 [1.01–1.66]), and South Asians were not significantly different from whites. Furthermore, sex did not modify the association between ethnicity and MI risk, except for Pacific Islanders where women had a markedly higher risk (1.94 [1.40–2.68]) than men (0.87 [0.59–1.27]; P for interaction = 0.001).
HRs and 95% CIs for each ethnic group (vs. whites [reference group]) for each diabetes complication.
The total number of first-time diagnoses for CHF was 5,062 during follow-up. The highest age- and sex-adjusted incidence was among African Americans (5.2 per 1,000 person-years), and the lowest incidence was among Chinese (2.5 per 1,000 person-years). The range of CHF incidence rates among the four Asian groups was narrower for CHF than for MI (from 2.4 to 3.3). In fully adjusted models, there was no significant difference between African Americans, Filipinos, Pacific Islanders, and South Asians compared with whites. The risk of CHF was significantly lower for Latinos, Japanese, and Chinese compared with whites.
There were 4,825 strokes during follow-up. Similar to CHF, the age- and sex-adjusted incidence was highest among African Americans, and the lowest rates occurred among Japanese (2.8 per 1,000 person-years). The fully adjusted comparison with whites showed a similar pattern as CHF, with Latinos, Japanese, Chinese, and Filipinos having significantly lower risk than whites and the other ethnic groups having similar risk to whites.
There were 2,340 new cases of ESRD. The adjusted incidence of ESRD was not uniformly higher for all ethnic minority groups compared with whites; the incidence was lower among South Asians (1.1 per 1,000 person-years) and Chinese (1.9 per 1,000 person-years) compared with whites (2.4 per 1,000 person-years) and higher among all of the other groups. Aggregating all four Asian groups together (2.9 per person-year [95% CI 2.0–4.0]) obscured the wide range of ESRD outcomes among each of the subgroups. However, after adjusting for all potentially explanatory groups of variables, the hazards of ESRD were significantly higher for each ethnic group compared with whites, except for South Asians for whom the ESRD risk was similar to whites.
There were a total of 2,291 first-time cases of LEA. The highest age- and sex-adjusted incidence was among African Americans and Pacific Islanders (2.6 per 1,000 person-years for each), and the lowest rates were among Chinese and Filipinos (0.7 per 1,000 person-years for each). Compared with whites, all four Asian subgroups had significantly lower risk of LEAs, whereas risk for Pacific Islanders, African Americans, and Latinos was not significantly different than that in whites.
Restricting our Cox models to those with complete data on all covariates, we found some change in risk estimates among the ethnic groups with smaller numbers of patients (Pacific Islanders and South Asians), mainly for the macrovascular disease outcomes. For MI, the risk among Pacific Islanders compared with whites was attenuated (HR 1.03 [95% CI 0.38–2.81]), and the risk became somewhat stronger among South Asians (2.00 [0.97–4.12]). For CHF, the risk was strengthened among South Asians (2.26 [0.91–5.60]). Estimates for stroke, ESRD, and LEAs did not change substantively.