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 1,117,805 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 14.4, followed by Japanese Americans with 12.4, and Caucasians with 6.5 per 1,000 person-years. BMI was positively related to incidence, whereas educational achievement showed an inverse association. BMI and education did not explain the ethnic differences in risk and interacted significantly with ethnicity. After stratification, the respective HRs for Japanese Americans, Caucasians, and Native Hawaiians were 3.24, 1.26, and 1.11 when those with obesity were compared to the lowest BMI category, while the HRs were 0.71 in Caucasians, 0.91 in Japanese Americans, and 0.88 in Native Hawaiians when college educated persons were compared to individuals with ≤12 years of education.

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