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Updated: May 27, 2026

Rodent Estrous Cycle Monitoring Utilizing Vaginal Lavage: No Such Thing As a Normal Cycle
09:05

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Published on: August 30, 2021

The menstrual cycle through the lens of a wearable device: insights into physiology, sleep, and cycle variability

Alexander Gonzalez1, Johanna J O'Day2, Sarah C Johnson3

  • 1Wu Tsai Human Performance Alliance, Stanford University, Stanford, CA, USA. alex.gonzalez@stanford.edu.

NPJ Digital Medicine
|May 25, 2026
PubMed

Women on average have 450 menstrual cycles in a lifetime, but we lack a characterization of physiological biometrics across the cycle and lifespan. We analyzed 1.2 million days of data from 2596 women who logged 42,759 menstrual cycles and wore a device that collected sleep and biometric data including resting heart rate (RHR), heart rate variability, respiratory rate, skin temperature, and blood oxygen saturation level. We generated novel quantifications of daily biometrics across ages and cycle lengths, finding that cycle length is strongly associated with how much cardiorespiratory metrics vary across the cycle. We observed greater cycle variability for participants who slept 6 versus 8 hours. A within-participant natural experiment showed that decreased sleep resulted in biometric changes regardless of cycle phase (e.g., RHR increased 1.2% with a 10% decrease in weekly sleep duration). These results lay a foundation to better understand and optimize female health and performance.

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