Abstract 231: Decreased Parasympathetic Activity in the Ovulatory Phase of the Menstrual Cycle
The Heart rate variability (HRV) power spectrum is a non-invasive index of parasympathetic and sympathetic branches of the autonomic nervous system (ANS). Sex hormone oscillations may affect autonomic nervous system function; however, no systemic difference in HRV across the menstrual cycle has been shown. The purpose of this study is to test the hypothesis that there are changes in HRV spectral power components across the menstrual cycle.
Method: Eleven women (24.4±3.6 years) volunteered for this experiment. Menstrual cycle phase was determined via basal body temperature mapping. Participants were tested once in each cycle phase. A 3 lead ECG was sampled at 1000 Hz. A piezoelectric force transducer, placed around the chest, recorded breathing rate. After 20 minutes of quiet seated rest, 5 minutes of data was collected in the upright seated position. Power spectral density analysis was performed on the R-R interval variations by fast Fourier transformation. The spectrum was divided into low (0.04-0.15, Hz) and high (0.15-0.40 Hz) frequency components. In order to attain data normality, the components were transformed with a natural logarithm. A repeated measures ANCOVA was used with a piece-wise covariate function for breathing rates higher and lower than 10 breaths per minute.
Results: A significant decrease in total power spectrum was observed at the ovulatory phase (P=0.04) compared to the early follicular, late follicular and mid luteal phases. Furthermore, high-frequency oscillations were lower (P=0.04) in the ovulatory phase compared to late follicular phase. There were no changes observed (P>0.05) in the low frequency power spectrum across the menstrual cycle.
Conclusions: The decrease in the high-frequency components of the HRV power spectrum during the ovulatory phase indicates a decrease in parasympathetic regulation of the heart. The ovulatory phase is characterized by an elevated level of progesterone, follicle stimulating and luteinizing hormones, and a moderate level of estradiol. Thus, the changes in these hormones during ovulation appear to affect ANS function.
- © 2013 by American Heart Association, Inc.