HRV & Sleep

Methods

Comprehensive review of HRV in OSA, COPD, and overlap syndrome

Key Findings

• Overlap syndrome shows synergistic autonomic dysfunction
• 1.7x greater risk of acute exacerbations vs COPD alone
• Short-term HRV particularly sensitive to autonomic changes
• Wearables viable for screening in overlap syndrome
• CPAP therapy efficacy can be evaluated via HRV

Limitations

Review of existing literature

Methods

Continuous monitoring of HR and HRV circadian rhythms during pregnancy

Key Findings

• Autonomic nervous system regulates pregnancy adaptations
• HR and HRV circadian patterns change during pregnancy
• Circadian rhythm parameters may predict complications
• Non-invasive biomarker potential for maternal health

Limitations

Further research needed on complication prediction

Methods

13,217 person-years of follow-up on 4,170 participants with sleep HRV monitoring

Key Findings

• Unusually high and erratic HRV predicted later stroke development
• Persistently low HRV was common in those who later developed depression
• HRV patterns changed years before clinical diagnosis
• Sleep HRV provides unique predictive value beyond waking measures

Limitations

Observational study, specific thresholds not yet established

Methods

Systematic review and meta-analysis of 11 RCTs with 549 participants

Key Findings

• RMSSD significantly decreased after sleep deprivation (p < 0.05)
• LF power significantly increased (sympathetic activation)
• LF/HF ratio significantly increased after sleep loss
• Effects consistent across different sleep deprivation protocols

Limitations

Heterogeneous study designs, mostly acute sleep deprivation

Methods

Binary logistic regression model on pre-sleep HRV data from national-level male athletes

Key Findings

• 96% accuracy in predicting chronic insomnia from pre-sleep HRV
• Pre-sleep HRV reflects autonomic state affecting sleep onset
• Athletes with insomnia show distinct pre-sleep HRV patterns
• Model more accurate than self-reported sleep quality measures

Limitations

Male athletes only, specific to elite populations

Methods

AHA scientific statement review of adolescent cardiovascular health

Key Findings

• Late sleep timing associated with lower HRV in teens
• Weekend-weekday sleep differences correlated with reduced HRV
• Social jet lag impacts autonomic function
• Early intervention may prevent long-term effects
• Screen time before bed exacerbates circadian disruption

Limitations

Observational data, many confounding factors in adolescence

Methods

Longitudinal wearable monitoring in chronic pain patients

Key Findings

• Higher nighttime HR predicts higher next-day pain
• Autonomic hyperactivation precedes pain increases
• Relationship holds for both fibromyalgia and chronic back pain
• Suggests causal role of sympathetic activation in pain
• May enable predictive pain management

Limitations

Correlation study, individual thresholds vary

Methods

Polysomnography studies comparing HRV in OSA patients vs healthy controls

Key Findings

• OSA patients had 20-40% lower overnight RMSSD
• HRV suppression correlated with apnea severity (AHI)
• CPAP treatment improved HRV within 2-4 weeks
• Untreated OSA associated with increased cardiovascular risk

Limitations

Severity varies widely; mild OSA may have minimal HRV impact

Methods

Analysis of continuous HRV data from Oura Ring users over multiple weeks

Key Findings

• 5+ nights of data needed for reliable HRV-CV estimation
• Higher HRV-CV associated with alcohol consumption
• Higher HRV-CV linked to lower physical activity levels
• Higher HRV-CV correlated with inconsistent sleep schedules

Limitations

Observational data, correlation not causation

Methods

Analysis of wearable HRV data correlated with self-reported alcohol intake

Key Findings

• 1-2 drinks suppress HRV for approximately 2 days
• 3+ drinks can affect HRV for 4-5 days
• Effect is dose-dependent and cumulative
• Sleep quality also impaired during recovery period

Limitations

Self-reported alcohol intake may be underestimated

Methods

Binary logistic regression model using pre-sleep HRV in elite athletes

Key Findings

• Pre-sleep HRV predicted chronic insomnia with 96% accuracy
• Lower pre-sleep HRV associated with insomnia diagnosis
• Simple measurement could screen for sleep disorders
• Athletes with insomnia showed distinct HRV patterns

Limitations

Elite athlete population may not generalize, single study

Methods

Cross-sectional analysis of sleep duration, exercise, and HRV relationships

Key Findings

• Sleeping 6+ hours had protective effect on HRV
• Short sleep impaired restorative processes
• Inadequate exercise + short sleep = lowest HRV
• Sleep may be more foundational than exercise for HRV

Limitations

Cross-sectional design cannot establish causation

Methods

Polysomnography study measuring HRV reliability across sleep stages

Key Findings

• High-frequency HRV reliable across N2, deep sleep, and REM
• Correlations ranged from r=0.70 to r=0.88 across stages
• Reliability maintained even during disrupted sleep
• Supports overnight HRV as valid health metric

Limitations

Lab-based study may differ from home monitoring