Effects of anxiety during mental arithmetic stress on heart rate variability in healthy subjects

Aim: Anxiety may cause an increased risk of myocardial infarction by reductions in heart rate variability (HRV). However, no data exists on the effect of anxiety on a standard mental test of HRV. The aim of this study was to evaluate the association between anxiety elicited by mental stress and HRV. Methods: Effect of anxiety in the actual state (A-State) and in everyday life (A-Trait) has been assessed in 13 healthy subjects and its association to low (LF) and high-frequency (HF) of HRV during mental arithmetic stress has been tested through correlation analysis. Results: A significant increase from baseline through arithmetic stress was observed in the LF component (LF(nu) from 56.87 ± 4.2 to 73.5 ± 2.1; LnPLF(ms2) from 6.2 ± 0.2 to 7.1 ± 0.3) and in LF/HF ratio (from 2.6 ± 0.6 to 5.8 ± 0.8), while HF(nu) showed a significant decrease (from 33.5 ± 3.9 to 17.3 ± 1.9) (p<0.001 for all). A negative correlation has been found between the baseline and post-arithmetic stress A-State values and LF(nu) during mental stress (r=-0.68, p<0.02), while a positive correlation has been found between the baseline and post-arithmetic stress A-State values and the value of HF(nu) during mental stress (r=0.69 and r=0.68, respectively, p<0.01). Conclusions: Mental activity affects HRV by an increase of sympathetic component and a decrease of vagal activity. On mental stress, subjects with higher level of anxiety have higher vagal tone and lower sympathetic activation. This observation should be considered when assessing effects of the emotional circumstances on HRV.