Chronic Pain & Fatigue

Methods

Clinical trial with linear and nonlinear HRV analysis

Key Findings

• HRV grade positively correlated with symptom severity (r=0.51)
• FM patients have significantly lower HRV than controls
• Impaired HRV reactivity to stress predicts worse outcomes
• Higher anxiety and depression associated with lowest HRV
• Some patients cluster with near-normal HRV and better outcomes

Limitations

Cross-sectional design, individual variation high

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

Exercise challenge with continuous HRV monitoring

Key Findings

• ME/CFS patients took ~8 minutes for HRV recovery vs controls
• Sympathetic nervous system remained overactivated post-exercise
• Parasympathetic system failed to engage during recovery
• Demonstrates reduced functional capacity for exercise
• May explain post-exertional malaise mechanism

Limitations

Small sample, short exercise challenge

Methods

Prospective treatment study with baseline HRV assessment

Key Findings

• Higher HRV: 9.7 fewer headache days/month after treatment
• Lower HRV: only 6.2 fewer headache days/month
• Autonomic dysfunction common in chronic migraine
• HRV may serve as treatment response predictor
• HRV lowest during migraine attacks (ictal period)

Limitations

Single treatment studied, replication needed