Antioxidant vitamin C improves endothelial function in obstructive sleep apnea

Grebe M

Published in American Journal of Respiratory and Critical Care Medicine

Methodology

Controlled mechanistic study with blinded assessment; brachial artery flow-mediated dilation measured by ultrasound before and after intravenous injection of 0.5 g vitamin C in OSA patients and matched controls.

Key Findings

Flow-mediated dilation of the brachial artery was measured in 10 otherwise healthy untreated patients with obstructive sleep apnea and 10 age- and sex-matched controls, before and after intravenous vitamin C. Baseline flow-mediated dilation was significantly reduced in the OSA patients compared with controls. After 0.5 g intravenous ascorbate, vasoreactivity was unchanged in controls but rose in the OSA patients to a level comparable with the control group.

Conclusions

The reduced endothelial-dependent vasodilation in untreated patients with OSA acutely improves by the free radical scavenger vitamin C.

Limitations

Very small mechanistic study (10 per group) using a single intravenous dose and a surrogate vascular endpoint; it says nothing about oral vitamin C supplementation or clinical outcomes.