Sleep Duration and Incidence of Type 2 Diabetes: the Multiethnic Cohort

Objectives: As an emerging risk factor for the rising incidence of type 2 diabetes, we examined sleep duration in relation to type 2 diabetes and several biomarkers.

Design: Prospective cohort recruited 1993-1996.

Setting: The Multiethnic Cohort in Hawaii and California.

Participants: A cohort of 151,691 White, African American, Japanese American, Native Hawaiian, and Latino participants; 9695 cohort members had biomarker measurements.

Measurements: Sleep duration was self-reported at cohort entry. Diabetes status was obtained from 3 questionnaires and confirmed by 3 administrative data sources. Biomarkers were measured by standard assays 9.6±2.1 years after cohort entry. We estimated diabetes risk as a time-varying outcome using Cox regression adjusted for body mass index assessed at 3 time points and other known confounders and computed adjusted means of biomarkers by sleep hours.

Results: During 7.9±3.5 years of follow-up, 8487 new diabetes cases were diagnosed. Long sleep duration (≥9 hours), as compared with 7-8 hours, was significantly associated with higher incidence (hazard ratio, 1.12; 95% confidence interval 1.04-1.21), but the 4% elevated incidence for short sleep duration (≤6 hours) did not reach significance (95% confidence interval 0.99-1.09). After stratification, the associations appeared stronger in Japanese American than other ethnic groups and in participants without comorbidity. Hours of sleep were positively associated with C-reactive protein and triglycerides and inversely related to high-density lipoprotein cholesterol and adiponectin but not with leptin levels and homeostatic model assessment of insulin resistance.

Conclusion: In this multiethnic population, the 12% higher diabetes risk for long sleep hours may be mediated through inflammation, a poor lipid profile, and lower adiponectin levels.