Oral Contraceptive Pill Phase Does Not Influence Heart Rate Variability, Measured Using The Oura® Ring.

Heart rate variability (HRV) is the shift in timing between successive heart cycles and has been shown to be an indicator of overall health. Some research has found that HRV increases from the follicular to the luteal phase of the menstrual cycle, however these findings are not universal, and limited studies investigate the oral contraceptive pill (OCP) cycle. Moreover, all the current studies investigating the influence of hormonal cycle phase on HRV use in-lab techniques, such as research grade electrocardiogram monitoring. The OURA® smart ring allows for assessment of an index of HRV in free living situations. PURPOSE: To investigate the influence of OCP phase on HRV, measured using the OURA® smart ring. METHODS: This study included 14 premenopausal females using a second generation OCP, who wore the OURA® smart ring during both the active (days 14-21) and placebo (21-28) weeks of the OCP cycle. Root mean square of successive differences in heart rate was calculated from the OURA® smart ring nocturnal heart rate data using the 250 Hz infrared photoplethysmography, and the average across each cycle phase (3-5 days) was used. Data were analyzed using a Welch’s t-test, and all data are reported as mean ± SD, with α criterion set to 0.05. RESULTS: No difference in HRV was observed between the phases of the OCP cycle (Active: 63.4 ± 21.2 ms, Placebo: 67.8 ± 21.2 ms, p = 0.59, d = 0.21). CONCLUSION: These findings suggest no influence of OCP phase on HRV in young, healthy females. Future research should focus on the potential regulatory mechanisms by which estrogen and progesterone could influence autonomic function. Additionally, robust assessment of the validity and reliability of wearable HRV monitoring systems, such as the OURA® smart ring, must be conducted. Supported by: Natural Sciences and Engineering Research Council of Canada