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Updated: Apr 1, 2026
Ultrasound Assessment of Endothelial-Dependent Flow-Mediated Vasodilation of the Brachial Artery in Clinical Research
Published on: October 22, 2014
Brachial artery endothelial function is stable across the morning in young men
Saurabh S Thosar1, Chad C Wiggins2, Steven A Shea3,4
1Oregon Institute of Occupational Health Sciences, Oregon Health and Science University, L 606/RJH 1553 A, 97139, Portland, Oregon, USA. thosar@ohsu.edu.
Insights
Vascular endothelial function (VEF) remains stable in healthy young men during the morning hours, a period typically associated with increased cardiovascular risk. This study found no impairment in VEF despite typical daily activities.
Area of Science:
- Cardiovascular Physiology
- Endothelial Function
- Circadian Rhythms
Background:
- Morning hours are linked to higher cardiovascular disease (CVD) risk.
- Vascular endothelial function (VEF) is a key predictor of CVD.
- Diurnal variations in VEF are known, but morning-specific changes require further documentation.
Purpose of the Study:
- To investigate potential impairments in VEF during the vulnerable morning period.
- To assess VEF stability in healthy individuals from 0700 to 1300 h.
Main Methods:
- Eight healthy men participated in the study.
- VEF was assessed every 2 hours from 0700 to 1300 h on two separate days.
- Flow-mediated dilation (FMD) after brachial artery occlusion was used to estimate VEF.
Main Results:
- No significant alterations in FMD were observed across the 6-hour morning period.
- The hyperemic shear stimulus remained consistent throughout the assessment window.
- These findings held true despite variations in physical activity and meal intake.
Conclusions:
- VEF is stable in healthy young men during the morning hours, even with typical behaviors like breakfast and physical activity.
- Further research is needed to explore the influence of sleep, physical inactivity, and circadian rhythms on VEF.
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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