Abstract Body: Emerging evidence suggests a potential relationship between sleep and cardiac abnormalities, even in the absence of apnea. Therefore, we aimed to test the association of sleep duration and cardiac structure and function as assessed by echocardiography in African Caribbeans aged 50-80 years from the Tobago Heart Study (THS). Between 2021-2024, participants without history of heart failure underwent clinical examinations, 4 to 7-day actigraphy-based sleep assessment, and transthoracic echocardiography (preliminary analysis of 401 participants with all measures). Echocardiograms were analyzed by a central core lab with measures including left ventricular ejection fraction (EF), diastolic function, and left ventricular hypertrophy (LVH), among other indices. Statistical analyses tested the association of 24-hour sleep duration or nighttime sleep (between 8PM-8AM) with echocardiographic parameters adjusted for age, sex, BMI, systolic blood pressure, diabetes, smoking, snoring frequency, and heart rate using linear or logistic regression, as appropriate. The cohort was middle-aged (mean 60 years), predominantly female (89%), hypertensive (73%), and obese (median BMI 31 kg/m²). Mean 24-hr sleep duration was 5.8 hours (range=2-9 hours, median=5.5 hours), with a mean nighttime sleep duration of 5.5 hours. In adjusted models, longer nighttime sleep duration was not associated with echocardiography indices. However, when limited to just individuals who slept at least 5 hours at night, a 1-hour greater nighttime sleep duration was associated with ~5% lower left atrial volume index and ~5% lower pulmonary vascular resistance (P=0.01 for both). In contrast, nighttime sleep duration was not associated with left ventricular EF (b = -0.03 (-0.73 to 0.67), P=0.93). Results were similar when testing 24-hour sleep duration. Overall, among African Caribbean adults who sleep more than 5 hours per night, greater sleep duration may be associated with less risk of atrial fibrillation or pulmonary hypertension. This may be particularly relevant given that the African Caribbean population is at high risk for both hypertensive-related cardiac abnormalities and short sleep duration.