Abstract
Background: The autonomic nervous system plays an important role for maintaining vital functions in our body. The balance between sympathetic and parasympathetic systems is essential in maintaining homeostasis. Heart rate variability (HRV) refers to the beat-to-beat variation in heart rate generated by the interplay of sympathetic and parasympathetic nerve activity at the sinus node of the heart. It has been used as a non-invasive tool to analyze the influence of the autonomic nervous system on the heart. The importance of HRV as a tool for assessing the autonomic nervous system activity in many different diseases and conditions has steadily increased. In addition to frequently used long-term HRV analysis, short-term HRV analysis has been increasingly applied due to its suitability for ambulatory care and short-term patient monitoring and due to the almost instant availability of test results.

Aims and Objectives: This study aimed at finding out gender differences in cardiac autonomic function tests in normal healthy individuals.

Materials and Methods: This cross-sectional study was done on 20 male and 20 female subjects. Ethical committee clearance was taken before the start of the study and written informed consent was obtained from every individual. HRV tests were computed by recording lead II electrocardiogram on RMS polyrite-D machine. It included frequency domain variables such as low-frequency (LF) band, the high-frequency (HF) band, and the LF/HF ratio and time domain parameters such as standard deviation of all RR intervals over the selected time intervals (SDNN) and root mean square of successive differences between adjacent RR intervals (rMSSD). The values were tabulated and statistical analysis was done using unpaired t-test. P < 0.05 was considered statistically significant and <0.001 as highly statistically significant.

Results: In our study, all the frequency domain variables were relatively increased in males as compared to females except HF parameter, though statistically not significant. The values for rMSSD and SDNN were found to be relatively higher in females than males.

Conclusion: This study suggests that there are gender differences in HRV in normal healthy individuals. A relatively increase in sympathetic drive in men could indicate an increased risk of cardiovascular diseases. However, such studies need to be done in larger group of population to get better results.

Key words: Gender; Autonomic Nervous System; Heart Rate Variability; Cardiovascular