Objective: The purpose of this study was to investigate age and sex-dependent changes in heart rate variability (HRV) in healthy subjects, specifically the changes during the third decade.
Methods: Heart rate (HR), standard deviation of N-N interval (SDNN), high-frequency (HF), low-frequency (LF), total-power (TP), and ratio of LF and HF (LF/HF) were computed in 99 healthy subjects (Male: 64, Female: 35) using the APG Heart-Rater (Tokyo-Iken, Co., Ltd., Inagi-city, Tokyo). HF, LF and LF/HF ratio were logarithmically transformed before analysis, and regression analysis was performed to evaluate the correlation between age and heart rate dynamics. Subjects were subsequently divided into 3 groups based on age (twenties, thirties, and forty-plus) and gender, and multiple comparisons between the age groups were carried out.
Results: All HRV parameters except Ln LF/HF ratio showed significant negative correlations with age in both men and women, and all of the correlations were stronger in men than women. Men demonstrated higher values than women across all HRV parameters during twenties and thirties, whereas each of the HRV parameter of women was higher than men in the forty-plus group.
Conclusion: In general, autonomic and parasympathetic activities attenuate with age in both genders. A significant decline in overall autonomic and parasympathetic functions of men in their thirties may be associated with the feeling of sudden decrease in physical strength after age 30. Conversely, a more gradual decline in total autonomic and parasympathetic functions in women in later life may account for their greater longevity than men.