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 (ΔEE) 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 (ΔSBP), changes in HR (ΔHR) and changes in LF/HF (ΔLF/HF) in relation to ΔEE were represented by linear regression. Regression analysis showed that the coefficients of ΔEE were positively related to the dependent variables ΔSBP, ΔHR and ΔLF/HF. The slopes of the regression curves for the high-BP group (24-h SBP ≥127 mmHg) and the high-salt–intake group (≥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.