Abstract

Objective: Using the Hawaii component of the Multiethnic Cohort (MEC), we estimated diabetes incidence among Caucasians, Japanese Americans, and Native Hawaiians.

Research Design and Methods: After excluding subjects who reported diabetes at baseline, 93,870 cohort members were part of this analysis. New cases were identified through a follow-up questionnaire (1999-2000), a medication questionnaire (2003-2006), and linkage with two major health plans (2007). We computed age-standardized incidence rates and estimated hazard ratios (HR) for ethnicity, body mass index (BMI), and education using Cox regression.

Results: After a total follow-up time of 1,119,224 person-years, 11,838 incident diabetes cases were identified with an annual incidence rate of 10.4 per 1,000 person-years. Native Hawaiians had the highest rate with 15.5, followed by Japanese Americans with 12.5, and Caucasians with 5.8 per 1,000 person-years; the adjusted HRs were 2.65 for Japanese Americans and 1.93 for Native Hawaiians. BMI was positively related to incidence in all ethnic groups. Compared to the lowest category, the respective HRs for BMIs of 22.0-24.9, 25.0-29.9, and ≥30.0 kg/m² were 2.10, 4.12, and 9.48. However, the risk was highest for Japanese Americans and intermediate for Native Hawaiians in each BMI category. Educational achievement showed an inverse association with diabetes risk, but the protective effect was limited to Caucasians.

Conclusions: Within this multiethnic population, diabetes incidence was two-fold higher among Japanese Americans and Native Hawaiians than Caucasians. The significant interaction of ethnicity with BMI and education suggest ethnic differences in diabetes etiology.