Why Sleep HRV Matters
Sleep is when your body does its deepest recovery work, and HRV during sleep provides the clearest window into your autonomic health. Unlike daytime readings affected by activity, caffeine, and stress, sleep HRV reflects your true baseline.
Most wearables (Oura, Whoop, Garmin, Apple Watch) measure HRV during sleep for this reason. The readings are more consistent and more predictive of recovery status than daytime measurements.
When HRV is Measured During Sleep
Different devices measure at different times:
During deep sleep (Oura, Whoop): HRV is measured during your most restorative sleep phases, typically in the first half of the night. This captures peak parasympathetic activity.
Throughout the night (Garmin): Samples are taken periodically and averaged, giving a broader picture but potentially more variability.
Night average (most devices): The number you see in the morning is usually an average or representative sample, not a single reading.
For reliable baselines, research suggests you need at least 5 nights of data.
Average Sleeping HRV by Age
Sleep HRV tends to be higher than waking HRV because your parasympathetic system is more active at rest. Typical ranges:
| Age | Average Sleep RMSSD | |-----|---------------------| | 20s | 45-90ms | | 30s | 40-75ms | | 40s | 35-60ms | | 50s | 30-50ms | | 60+ | 25-45ms |
These are rough averages—individual variation is significant. Your personal trend matters more than comparing to population norms.
What Affects Sleep HRV
Factors that lower sleep HRV: - Alcohol (even small amounts) - Late eating (within 2-3 hours of bed) - Poor sleep environment (too warm, noisy, light) - Stress and anxiety - Illness or fighting infection - Hard training that day - Sleep disorders (apnea, restless legs)
Factors that raise sleep HRV: - Consistent sleep schedule - Cool, dark bedroom - Good sleep hygiene - Regular exercise (not too close to bed) - Stress management - Recovery days after hard training
Sleep HRV Patterns to Watch
Healthy pattern: HRV is highest in the first part of the night during deep sleep, then may decline slightly toward morning as you cycle through lighter sleep phases.
Warning signs: - HRV that's suppressed all night (poor recovery) - Large night-to-night swings (inconsistent sleep quality) - Steady decline over weeks (accumulating stress or overtraining) - Much lower than your personal baseline
Good sign: HRV rebounds after rest days, returning to or exceeding baseline.
Improving Your Sleep HRV
The same factors that improve sleep quality improve sleep HRV:
1. Consistent schedule: Same bedtime and wake time, even weekends 2. No alcohol: Or at least none within 4 hours of bed 3. Cool room: 65-68°F (18-20°C) is optimal for most people 4. Early dinner: Finish eating 3+ hours before bed 5. Wind down: Reduce stimulation in the hour before sleep 6. Morning exercise: Better for HRV than evening workouts 7. Address sleep disorders: Apnea significantly suppresses HRV
Improvements typically appear within 1-2 weeks of consistent changes.
Research: Browse sleep and HRV studies for the latest findings on sleep quality, duration, and heart rate variability.