Gregory J. Grosicki, Jason R. Carter, Paul B. Laursen, Daniel J. Plews, Marco Altini, Andrew J. Galpin, Finnbarr Fielding, William von Hippel, Christopher Chapman, Summer R. Jasinski, Ursula K. Beattie, Kristen E. Holmes
We identify HRV-CV measured during sleep as a scalable measure of day-to-day HRV fluctuation. Analyzing nearly 2 million HRV readings from >21,000 individuals, we document that five nights are sufficient for reliable 7-day estimates. Higher HRV-CV is associated with greater alcohol consumption, lower activity, shorter and less consistent sleep, older age, and higher BMI. These findings provide the first large-scale characterization of HRV-CV and support its potential as a biomarker for behavioral monitoring and risk stratification.