Phase-Dependent Changes in Heart Rate Variability During the Menstrual Cycle in Healthy Young Women at a Tertiary Care Center.

Background The menstrual cycle is characterized by cyclical hormonal fluctuations of estrogen and progesterone that influence multiple physiological systems, including the cardiovascular and autonomic nervous systems. Heart rate variability (HRV) is a widely accepted, non-invasive method for assessing autonomic nervous system activity. This study aimed to evaluate HRV across different phases of the menstrual cycle in young, healthy female students. Methodology This observational study was conducted in the Department of Physiology at Maharishi Markandeshwar Institute of Medical Sciences and Research (MMIMSR), Mullana, Ambala, over 18 months. Fifty healthy female students aged 18-30 years with regular menstrual cycles were included. HRV was recorded using electrocardiography during the menstrual, proliferative, ovulatory, and secretory phases. Frequency-domain parameters were analyzed using SPSS software (IBM SPSS Statistics for Windows, IBM Corp., Version 23.0, Armonk, NY). Results Fifty healthy women (mean age: 20.3 ± 2.6 years) were included. High-frequency (HF) power varied significantly across menstrual phases (F = 15.28, p < 0.001), increasing from 807 ± 949 ms² during the menstrual phase to 2118 ± 2013 ms² in the proliferative phase and 1753 ± 1498 ms² during ovulation before decreasing to 912 ± 1194 ms² in the secretory phase. Low-frequency (LF) power also showed significant phase-dependent variation (F = 8.48, p < 0.001), whereas the LF/HF ratio did not differ significantly between phases (F = 0.74, p = 0.529). Post hoc analysis demonstrated significantly higher HF power during the proliferative and ovulatory phases compared with the menstrual and secretory phases (all p ≤ 0.002), indicating greater parasympathetic activity during estrogen-dominant phases. Conclusion HRV demonstrates phase-dependent variation across the menstrual cycle, with increased parasympathetic activity during the proliferative and ovulatory phases. Consideration of the menstrual phase is important when interpreting HRV findings.