Excess incidence of known non-insulin-dependent diabetes mellitus (NIDDM) in Hispanics compared with non-Hispanic whites in the San Luis Valley, Colorado

Abstract

Non-insulin-dependent diabetes mellitus is between two and five times more prevalent among Hispanic Americans than among non-Hispanic whites (NHW). Incidence data for Hispanic populations will help to determine whether this excess prevalence is due to increased incidence, survivorship, or other factors. Incident cases were identified through concurrent surveillance of all local medical practices from 1983 to 1988 in two southern Colorado counties in which the population was 46% Hispanic. All identified subjects were invited for an oral glucose tolerance test. Among the subjects who attended clinic, 83% were confirmed as having diabetes, using WHO criteria. The standardized average annual incidence rates per 1000 for confirmed non-insulin-dependent diabetes, accounting for nonresponse, were 3.7 and 1.6 for Hispanic and NHW males, and 4.5 and 1.2 for Hispanic and NHW females, respectively. The age and nonresponse adjusted rate ratio comparing Hispanics to NHWs was 3.1 (95% CI: 2.3-4.2), indicating a significant excess risk of diabetes incidence for the Hispanic population in southern Colorado. Peak age-specific incidence among Hispanics occurred in persons 50 to 59 years old, a decade earlier than among NHWs. These results are consistent with data from the Mexican-American population in Texas and suggest that the previously observed excess in diabetes prevalence is due to higher incidence rates. The earlier age-specific peak in incidence has also been observed in Mexican-American and American Indian populations, suggesting that risk factors may operate at earlier ages.