Diabetes is a serious, costly, and potentially preventable public health problem in the United States (1--3). Both the prevalence and incidence of diabetes have increased rapidly since the mid-1990s, with minority racial/ethnic groups and socioeconomically disadvantaged groups experiencing the steepest increases and most substantial effects from the disease (1, 4--6).

To assess disparities in the prevalence and incidence of medically diagnosed diabetes, CDC used data from the 2004 and 2008 National Health Interview Survey (NHIS), an ongoing, cross-sectional, in-person household interview survey of the civilian, noninstitutionalized US population. A randomly selected adult (aged≥ 18 years) in each family was asked whether they had ever been told by a health-care professional that they had diabetes; those who reported having diagnosed diabetes were asked the age at which they received the diagnosis. Respondents who were the same age when interviewed as when they received a diabetes diagnosis were considered to have a case of incident diabetes (Age at interview--Age at diagnosis= 0 years). In addition, half of the cases among respondents who were aged 1 year older when they were interviewed than when they received the diagnosis were counted as incident cases (Age at interview--Age at diagnosis= 1 year). Both the values for age at interview and age at diagnosis were rounded to the nearest year; therefore, among respondents with a difference of 1 year (Age at interview--Age at diagnosis= 1 year), the actual duration with diagnosed diabetes was in the interval (0, 2). Durations were assumed to be spread uniformly over the interval (0, 2), and half were assumed to be within 1 year of diagnosis. Prevalence (cases of diabetes of any duration per 100 population) was calculated for adults aged≥ 18 years. Incidence (cases of diabetes≤ 1 year's duration per 1,000 population) was calculated for adults aged 18--79 years.