Sex differences in forearm vasoconstrictor response to voluntary apnea

Area of Science:

• Cardiovascular Physiology
• Sleep Medicine
• Sex Differences in Physiology

Background:

• Obstructive sleep apnea is more prevalent and severe in men than women.
• Sex differences in sympathetic responses to hypoxemia may explain this clinical observation.

Purpose of the Study:

• To investigate sex differences in acute physiological responses to maximal voluntary end-expiratory apnea (MVEEA) in young and older adults.
• To determine if female sex hormones influence vasoconstrictor responses during apnea.

Main Methods:

• Healthy young and older men and women underwent MVEEA.
• Measurements included mean arterial pressure (MAP), heart rate (HR), brachial artery blood flow velocity (BBFV), and cutaneous vascular conductance (CVC).
• Changes in physiological parameters were compared between sexes and age groups.

Main Results:

• Breath-hold duration and oxygen saturation nadir were similar across all groups.
• Young women showed significantly blunted forearm vasoconstriction (ΔBBFV, ΔCVC) compared to young men.
• This attenuated vasoconstriction was not observed in postmenopausal women.

Conclusions:

• Young women exhibit a dampened forearm vasoconstrictor response to MVEEA compared to young men.
• This sex difference is not present in postmenopausal women.
• Female sex hormones likely play a role in modulating neurogenic vasoconstriction during apnea-induced hypoxemia.