Table 2.

Summary of Epidemiological Studies in America that Examine Sleep as a Mediating Factor for Ethnic Differences in Disease Risk

Source	Study Design	Sample	Results
Brown, 200960	Cross-sectional household interview survey	2005 National Health Interview Survey (NHIS); n=29818, aged 18–85 y	Adjusted risk of obesity associated with short sleep higher for blacks than whites (1.78, 95% CI: 1.30–2.45; 1.43, 95% CI: 1.24–1.66)
Knutson et al, 20096	Wrist actigraphy for 3 consecutive days from 2003–05	Ancillary Coronary Artery Risk Development in Young Adults study of Chicago residents, n=578, aged 33–45	Short sleep duration predicted incident hypertension (OR 1.37, 95% CI: 1/05, 1.78); sleep duration mediated difference between black and white Americans in diastolic blood pressure change over time (P=.02); short sleep and poor sleep maintenance predicted higher systolic and diastolic pressure and more adverse changes in systolic and diastolic blood pressure over 5 y (all P<.05) after adjusting for age, race, and sex and excluding those on anti-hypertensive medication
Knutson et al, 200665	Cross-sectional study	Black American volunteers with type 2 diabetes interviewed at the University of Chicago Hospitals, n=161; HbAlc levels from medical charts to measure glycemic control; PSQI to measure sleep quality	In patients without diabetic complications, perceived sleep debt, not PSQI, was a significant predictor of HbAlc level (r=.51, P=.04); in patients with at least 1 complication, PSQI score, not sleep debt, was a significant predictor of HbAlc level (r=.043, P=.002)

Abbreviations: CI, confidence interval