Peripheral Vascular Function is Not Correlated to Subjective Sleep Quality in Young Healthy Humans

Background: Peripheral vascular dysfunction (including endothelial dysfunction) may be an early biomarker of cardiovascular disease. Prior studies have shown a relationship between poor sleep quality and impaired vascular function, indexed by flow-mediated dilation (FMD) of the brachial artery. However, these investigations did not allometrically scale for baseline artery diameter, nor control for shear stress, which both affect the magnitude of flow-mediated vasodilation. Without scaling for baseline artery diameter, FMD may overestimate the magnitude of dilation in individuals with small baseline diameters. Additionally, greater shear stress will elicit a greater magnitude of vasodilation via release of vasoactive mediators from the endothelium, such as nitric oxide. With the quality of sleep declining in the United States, and cardiovascular disease remaining a leading cause of mortality, we sought to further explore the relationship between sleep quality and peripheral vascular function corrected for both baseline artery diameter and the magnitude of shear stress. Hypothesis: Poor sleep quality is associated with impaired peripheral vascular function indexed by "corrected” brachial artery FMD. Methods: Thirteen young and healthy human participants (7M, 6F) completed the Pittsburgh Sleep Quality Index (PSQI) survey prior to assessment of brachial artery FMD. PSQI scores range from 0-21, with higher scores indicating worse sleep quality. Brachial artery diameter and blood velocity were then obtained via duplex Doppler ultrasound during a 2-min baseline, a 5-min occlusion of the brachial artery, and a 3-min reactive hyperemia period. FMD of the brachial artery was calculated as the percent change from baseline diameter to the maximum diameter induced by reactive hyperemia. Shear stress was estimated as shear rate, calculated as eight times the ratio of brachial artery blood velocity to diameter. FMD was corrected for baseline diameter, and the shear stress area under the curve up to maximum diameter via ANCOVA (i.e., "corrected FMD”). Pearson correlations were calculated between PSQI score and uncorrected FMD, and between PSQI score and ANCOVA corrected FMD. Results: The mean PSQI score was 5.3 ± 4.5 (range, 0-17), and mean FMD was 5.0 ± 2.2 % (range, 2.7-9.4 %). While an unexpected modest positive correlation was observed between uncorrected FMD and PSQI score (r=0.51, p=0.08), corrected FMD and PSQI score were not correlated (r=0.38, p=0.25). Conclusion: There was no relationship between subjective sleep quality and peripheral vascular function as measured by corrected FMD in this cohort of young and healthy participants. These findings likely reflect the multivariate nature of vascular function in young healthy adults with lower cardiovascular risk, and the subsequent narrow range of both flow-mediated dilation and subjective sleep quality.