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Introduction: Approximately half of the disparity in premature mortality between African American (AA) and European American (EA) adults is due to greater hypertension, diabetes, and stroke risk. The current study tests sleep as a mediator of racial disparities in cardiometabolic (CMB) disease risk in adulthood. Methods: A total of 618 CARDIA Study members took part in a sleep sub-study (2003-2005) and had measured CMB risk (2000-2011; mean age at baseline=40.1; 43.5% AA; 56.5% EA; 42.1% male). Sleep efficiency (% of time in bed asleep) and total sleep time were assessed via actigraphy for six total nights in years 17 and 18 of the CARDIA Study. CMB risk was assessed in years 15 and 25 from borderline high (coded as 1) and high (coded as 2) levels in seven markers using recommended cutpoints from NCEP ATP III and AHA: blood pressure, glucose, insulin resistance, waist circumference, triglycerides, HDL-C, and C-reactive protein. Scores were averaged across markers, ranging from 0 to 2 (a score of 1 indicates a borderline high average in the seven markers). Using linear path models, sleep variables were tested as mediators of racial disparities in ten-year changes in CMB risk. Results: AAs obtained less efficient sleep and less total sleep than EAs (76.5% vs 84.3%; 5.63 hrs vs. 6.43 hrs), and AAs had higher CMB risk at both periods (Mean at Y15: .75 vs. .55; Y25: .94 vs. .67) (p's < .001). Mediation tests are shown in the Table. Race was indirectly associated with increasing CMB risk over the ten-year period via sleep efficiency, explaining 25% of the racial disparity. Racial disparities in CMB risk were attenuated by 24.5% when adjusting for sleep time, although the mediation test was not significant. After adjusting for education and household income, 18.1% of the race disparity in diverging CMB risk was explained by sleep efficiency and 20.8% by sleep time. Conclusions: Differences in sleep likely contribute to greater CMB risk among AAs as compared to EAs in adulthood. Sleep may be an important intervention point to reduce racial health disparities. [ABSTRACT FROM AUTHOR]