Effect of physical and mental stress on heart rate variability in type-A and type-B personalities

INTRODUCTION: Stress is a huge problem which affects many physiological parameters in human body. In contrast with other lifestyle risk factors, no consensus about stress exists with respect to either definition or measurement. In particular, with reference to the ways in which people cope with stress, it was found convenient to postulate the existence of two separate personality types characterized by differing sets of behavior patterns known as Type A or Type B behavior (Friedman and Rosenman,1959). OBJECTIVE: The goal of our study was to evaluate the changes in heart rate variability due to physical and mental stress in different type of personalities (Type A and Type B) and to investigate a possible link between psychological traits and autonomic imbalance. METHOD: In laboratory set up, 25 subjects (9 males, 11 females; 5 rejected) of mean age 20.30 ±1.53 years were taken. After taking written consent, subjects were instructed to fill in personality questionnaire. In each of the subject, baseline ECG was recorded for 5 minutes and they were subjected to mental (reverse calculations) and physical stress (45 degree shoulder abduction) with 15 minutes interval period in between. Spectral analysis of HRV for our study, characterized by High frequency (HF) component, Low frequency (LF) component and LF/HF ratio. All the subjects were divided into Type A (Scores > 207), Type B (Scores <187) and AB (Scores in 188 to 207).Correlation was found between type of personalities and the frequency domain of HRV. RESULTS: All the components of HRV (LF, HF, LF/HF) were sensitive to physical and mental demands. Type A personality were more prone to stress, despite similar baseline values and stress tests to Type B personality. Statistically significant change in heart rate and thus RR interval was observed during the physical and mental stress as compared to resting condition in Type A individuals. Although personality scores gave positive correlation with HR, LF and LF/HF while negative correlation was seen with HF domain, but the correlation was not significant. Due to mental stress, significant increase in heart rate, LF domain and LF/HF ratio was seen as compared to physical stress. HF domain, although increased with physical stress, but it was not statistically significant. CONCLUSIONS: Both physical and mental stress influence risk factors that may increase risk for cardiovascular diseases especially in type A personality.