Mechanism explainer

HRV and Sleep Quality: What Heart Rate Variability Tells You About Your Sleep

Heart rate variability during sleep is a stage-specific physiological signal — not a single nightly score — that reflects how your autonomic nervous system shifts between parasympathetic dominance in deep sleep and sympathetic reactivation in REM. This article explains the mechanisms behind those shifts, what disrupted HRV patterns mean in insomnia and sleep apnea, how consumer wearables measure and differ in accuracy, and why your personal baseline trend matters far more than any population average.