NIDDM incidence in a tri-ethnic population of diagnosed hypertensives.

OBJECTIVE: Significant racial/ethnic differences exist in the prevalence of hypertension (HTN) and non-insulin dependent diabetes mellitus (NIDDM). The purpose of this study was to determine if ethnicity (African-American, Hispanic and non-Hispanic white) was related to NIDDM incidence over a maximum follow-up period of 10 years.

DESIGN: Retrospective cohort study.

SETTING: A large, urban public health care system serving over 200,000 predominantly minority persons. The system includes nine primary care health centers.

PATIENTS: African-American, Hispanic and non-Hispanic white patients with diagnosed hypertension who received primary care in the study setting.

METHODS: Medical records of 2,941 hypertensives free of NIDDM at their baseline visit were reviewed to document incident NIDDM during follow-up. Sociodemographic characteristics and physiologic covariates consistently available in the medical record (blood pressure, height, weight, and blood glucose) were also abstracted.

RESULTS: The mean age of patients at the baseline visit was 56 years; 67% were female, 63% were African-American. 17% Hispanic, and 20% non-Hispanic white. Two hundred thirty-six incident cases of NIDDM were identified in the cohort. In Cox proportional hazards analysis, the risk of developing NIDDM was not related to ethnicity either in univariate analysis or after adjusting for age, baseline blood glucose, and body mass index (adjusted RR for African Americans compared with whites = .82, 95% CI = .57-1.18; adjusted RR for Hispanics compared with whites = .84, 95% CI = .51-1.38).

CONCLUSION: The lack of association between ethnicity and NIDDM risk among hypertensives is unexpected, and may indicate differences in the pathogenetic mechanisms that underlie the development of hypertension and NIDDM in these three ethnic groups.