Circadian variation in endothelial function is attenuated in postmenopausal women

Area of Science:

• Cardiovascular Physiology
• Chronobiology
• Women's Health

Background:

• Endothelial function plays a crucial role in cardiovascular health.
• Circadian rhythms influence various physiological processes, including vascular function.
• Menopause is associated with an increased risk of cardiovascular disease in women.

Purpose of the Study:

• To determine if a circadian rhythm exists in endothelial function in women.
• To investigate whether menopause alters this circadian rhythm.
• To assess the impact of menopause on endothelium-dependent and -independent vasodilation.

Main Methods:

• Studied 11 pre-menopausal and 13 postmenopausal women under constant routine conditions over 22 hours.
• Assessed endothelium-dependent (flow-mediated dilation, %FMD) and -independent (glyceryl-trinitrate, GTN-mediated) function every 2-4 hours.
• Utilized high-resolution ultrasound of the brachial artery to measure vascular function.

Main Results:

• Postmenopausal women had significantly lower %FMD and %GTN compared to pre-menopausal women.
• Pre-menopausal women showed a significant day-night variation in %FMD.
• Postmenopausal women displayed an attenuated circadian rhythm in %FMD, with no significant day-night difference.

Conclusions:

• A circadian rhythm in endothelial function (%FMD) is present in pre-menopausal women.
• This circadian rhythm in %FMD is lost following menopause.
• The reduction in %FMD and loss of its circadian variation post-menopause may contribute to increased coronary heart disease risk in women.