Among white women, the hazard ratio for all-cause mortality on an adjusted analysis for those with diabetes was 2.2 (95% CI 2-2.36), while among blacks it was 2.11 (95% CI 1.83-2.44), according to Yunsheng Ma, MD, PhD, of the University of Massachusetts in Worcester, and colleagues.
Similar risks also were seen for Hispanic women (HR 2.3, 95% CI 1.72-3.23) as well as for those of Asian ancestry (HR 2.12, 95% CI 1.43-3.15), the researchers reported online in the American Journal of Epidemiology.
"Among people with diabetes in the United States, blacks and Hispanics are 2.1 times and 1.5 times more likely than whites to die of all causes, respectively, whereas total mortality among Asians is considerably lower compared with that among whites," they noted.
Because the potential for disparities in mortality among women with and without diabetes according to race or ethnicity has not been established, Ma and colleagues analyzed data from 158,833 participants in the ongoing WHI, which enrolled women between 1993 and 1998.
The participants' mean age was 63. A total of 84.1% were white, 9.2% were African American, 4.1% were Hispanic, and 2.6% were Asian.
At the time of enrollment, 4.4% reported having a history of diabetes diagnosis, and during an average duration of follow-up of 10.4 years, the cumulative incidence of diabetes was 5.45%.
Those who had diabetes at the time of enrollment typically had more comorbid conditions, had higher body mass index, engaged in less activity, and had poorer quality diets than those without diabetes.
The total percentages of women with diabetes, either prevalent or incident, by the cutoff point of August 2009 were 27.1% among black women, 20.8% for Hispanics, 15.9% among Asians, and 11.7% for white women.
In addition to all-cause mortality, similar risks across racial/ethnic groups were found for cardiovascular mortality and cancer death after adjustment for multiple factors including socioeconomic status, hypertension, hormone use, and smoking.
For cardiovascular death, the HRs for whites and blacks were 2.87 (95% CI 2.57-3.20) and 2.65 (95% CI 2.10-3.35), respectively, while they were 3.05 (95% CI 1.66-5.61) for Hispanics and 2.26 (95% CI 1.14-4.46) for Asians.
For deaths from cancer, the HRs among the four groups were 1.44 (95% CI 1.27-1.62) for whites, 1.38 (95% CI 1.05-1.81) for blacks, 2.13 (95% CI 1.30-3.47) for Hispanics, and 2.06 (95% CI 1.09-3.88) for Asians.
The researchers then calculated the population attributable risk percentages, which reflects both the disease prevalence and mortality risk, with these results for all-cause mortality:
For cardiovascular disease mortality, the population attributable risk percentages were highest for Hispanics at 30.6 (95% CI 8.7-49.7) and blacks at 25.9 (95% CI 17.8-33.7), and for cancer the risk percentages were highest for Hispanics and Asians, but the confidence intervals overlapped.
"Both black and Hispanic women, who are at higher-than-average risk of developing diabetes, had higher proportions of all-cause and [cardiovascular disease] mortality attributable to diabetes than did whites," the researchers noted.
"Because of [this] 'amplifying' effect of diabetes prevalence, efforts to eliminate racial and ethnic disparities in deaths from diabetes should focus on prevention of type 2 diabetes mellitus," they stated.
Strengths of the study included its large sample and prospective design, while limitations included self-report of diabetes and the lack of information on glycosylated hemoglobin or anti-diabetic medication use.