The effects of mental stress and the cold pressure test on flow-mediated vasodilation.

As a stressful lifestyle has been associated with coronary heart disease, this study aim to evaluate how two stressful tests influence endothelial-dependent vasodilation evaluated by flow-mediated dilation (FMD) of the brachial artery. FMD following 5 min of occlusion of the forearm was evaluated in young healthy volunteers with measurements of brachial artery diameter and blood flow (BABF) using ultrasound before and during a mental arithmetic task (MAT), and during cold pressure test (COP). MAT and COP increased blood pressure to a similar degree (18-21 mmHg). The COP induced a significant reduction in FMD compared to the baseline levels (from 9.3 +/- 3.9 to 5.9 +/- 3.2%, p < 0.01), as well as to the MAT, which in itself did not influence FMD (10.1 +/- 5.0%). However, as MAT increased BABF during hyperaemia significantly, the FMD to BABF ratio was significantly reduced by both stress tests (p < 0.05). Time-control experiments showed FMD measurements to be reproducible and that MAT and COP by themselves only marginally affected brachial artery diameter. In conclusion, cold pressure stress induced an impairment in FMD, but no effect was induced by a MAT. However, when FMD was normalized for the degree of hyperaemic blood flow, the driver of the vasodilation in the brachial artery, a reduction in flow-mediated vasodilation was seen during both mental and cold pressure stress.