Influence of mental stress on cardiovascular function as evaluated by changes in energy expenditure.

We assessed the influence of mental stress on cardiovascular parameters, including systolic blood pressure (SBP), heart rate (HR) and sympathetic activity (LF/HF), with the use of a quantitative indicator of energy expenditure (EE). Forty-four male university students underwent a mental arithmetic test. Their EE was 1.3-fold that at rest in response to the test. Change in EE (DeltaEE) in response to the test was compared between subjects with high blood pressure (BP) and those without and between subjects with high salt intake and those without. Changes in SBP (DeltaSBP), changes in HR (DeltaHR) and changes in LF/HF (DeltaLF/HF) in relation to DeltaEE were represented by linear regression. Regression analysis showed that the coefficients of DeltaEE were positively related to the dependent variables DeltaSBP, DeltaHR and DeltaLF/HF. The slopes of the regression curves for the high-BP group (24-h SBP >or=127 mmHg) and the high-salt-intake group (>or=11 g/day) were steeper than those for the normal BP group and the low-salt-intake group (p=0.11 and p=0.01, respectively). Thus, we were able to determine the influence of mental stress on cardiovascular function. The influence of mental stress on cardiovascular function likely differs according to a subject's environmental conditions. Our study implied that high salt intake increases the sensitivity of cardiovascular functions to mental stress.