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Objective: The environment in modern society could disturb the sleep-wake rhythm. We aimed to study the association of sleep-wake rhythm with endothelial function and sleep quality. Material and Methods: Thirty-one healthy university students (mean age: 20.4±1.8 years) were enrolled. The endothelial function was evaluated with the percent endothelium-dependent flow-mediated dilation of the brachial artery [%FMD: (maximum diameter - baseline diameter)/baseline diameter x 100] using the high-resolution ultrasonography. We also measured the total sleep time (TST), sleep effciency, and the standard deviation (SD) of sleep timing (midpoint between bedtime and wake-up time) using the actigraphy. The irregular sleep-wake rhythm was defined as having the shift of bedtime or wake-up time for two hours or longer. Results: The %FMD and sleep efficiency were significantly lower in the irregular group than regular group (%FMD: 6.1±2.4 vs. 10.9±2.3, p

Abstract Sleep disturbances and cognitive decline are common in older adults. We aimed to investigate the effects of the total sleep time (TST) and sleep–wake rhythm on executive function and working memory in older adults. In 63 older participants, we measured the TST, wake after sleep onset (WASO), and sleep timing (midpoint between bedtime and wake-up time) using actigraphy. Executive function was evaluated with the trail making test B (TMT-B) and Wisconsin card sorting test (WCST). The number of back task (N-back task) was used to measure working memory. Participants with a TST ≥ 8 h had a significantly lower percentage of correct answers (% correct) on the 1-back task than those with a TST