SLEEP-WAKE RHYTHM AND ENDOTHELIAL FUNCTION IN YOUNG ADULTS

Abstract

Objective: Insufficient sleep or short sleep duration is a risk factor for hypertension associated with cardiovascular disease in adults. Irregular sleep-wake rhythm is common problems among university students. We investigated the effect of sleep-wake rhythm or sleep duration on endothelial function in young adults. Design and method: Twenty university students were enrolled in this study. All subjects had no history of any neurological disorder, substance abuse, head injury or major physical illness, and were not on any psychotropic medications at the time of the study. There were no problems with social life in any subjects. The Chubu University ethics committee approved all procedures associated with the study. We obtained written informed consent from each participant after fully explanation of the protocol. All subjects filled a questionnaire about their daily sleep schedule. Bedtime, wake-up time, and sleep duration were collected from this questionnaire and median of sleep time was calculated. Peak cortical oxygenated hemoglobin and integral values by a word fluency task were measured with NIRS. Brachial-ankle pulsed wave velocity (baPWV), systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were measured using a plethysmograph. Endothelium-dependent FMD was induced by reactive hyperemia, and high-resolution ultrasound with a 7.5-MHz linear array transducer was used to measure the diameter of the right brachial artery. Percent FMD was computed as: (maximum diameter-baseline diameter) / baseline diameter × 100. Total sleep time (TST) and sleep-wake rhythm were evaluated by actigraphy. Results: Percent FMD was significantly lower in irregular sleep-wake rhythm group (greater than two hours) than in non-irregular sleep-wake rhythm group. Percent FMD was significantly greater in TST < 6 hours group than in TST>6 hours group. There were no significant differences in baPWV, SBP, DBP, HR, and baseline brachial artery diameter between the two groups. Conclusions: Irregular sleep-wake rhythm or short sleep duration may play an important role in decreasing endothelial function.