Key result
In healthy young men, vascular endothelial function measured by flow-mediated dilation remained stable across the vulnerable morning period from 0700 to 1300 hours (p=0.90).
Observational (n=8)
Single-blind
No
p-value: p=0.90
In healthy young men, vascular endothelial function remains stable across the vulnerable morning period (0700-1300 h) during typical daily behaviors like eating breakfast and light physical activity.
Stable morning FMD in healthy young men does not implicate endothelial dysfunction in circadian risk; leaves open relevance to older or higher-risk groups.
BACKGROUND: The morning hours are associated with increased cardiovascular (CV) risk, and vascular endothelial function (VEF) is a strong predictor of CV disease. A diurnal rhythm in VEF has been established but the morning variation in VEF is not well-documented. Thus, we tested if VEF is impaired across the vulnerable morning period. METHODS: After overnight fasts, eight healthy men (age 26.3 ± 3 yr) underwent assessments of VEF under standardized testing conditions every 2 h from 0700 to 1300 h on two separate days. VEF was estimated following 5 min brachial artery occlusions by hyperemic flow-mediated dilation (FMD). RESULTS: There was no significant change in FMD or hyperemic shear stimulus across the 6 h vulnerable period on either day, despite changes in physical activity and meals across these periods. CONCLUSION: In this healthy group of young men, VEF is stable across the vulnerable morning period when typical behaviors occurred (breakfast and physical activity). Future research should focus on the roles of sleep, physical inactivity during sleep and endogenous circadian rhythm in VEF.
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Thosar et al. (2015) conducted an observational in Healthy (n=8). Morning hours (0700-1300 h) was evaluated on Change in flow-mediated dilation (FMD) across the 6-hour morning period (p=0.90). In healthy young men, vascular endothelial function measured by flow-mediated dilation remained stable across the vulnerable morning period from 0700 to 1300 hours (p=0.90).
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