Autonomic Nervous System Functioning Related to Nocturnal Sleep in Patients With Chronic Fatigue Syndrome Compared to Tired Controls.
Orjatsalo, Maija, Alakuijala, Anniina, Partinen, Markku · Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine · 2018 · DOI
Quick Summary
This study examined how the nervous system controls heart rate and blood pressure during sleep in ME/CFS patients compared to people without the condition. Researchers found that ME/CFS patients showed unusual patterns during sleep: their sympathetic nervous system (the 'fight or flight' system) was more active than normal, while their parasympathetic nervous system (the 'rest and digest' system) was less active, especially during deep sleep. This abnormal nervous system activity during sleep may help explain why ME/CFS patients often wake up feeling unrefreshed.
Why It Matters
Unrefreshing sleep is a hallmark symptom of ME/CFS, yet its biological basis remains poorly understood. This study provides objective evidence of autonomic nervous system dysfunction during sleep in ME/CFS, suggesting that abnormal nervous system regulation—rather than simply poor sleep quantity or quality—may underlie sleep-related symptoms. Understanding these mechanisms could guide development of targeted treatments to improve sleep quality and overall functioning.
Observed Findings
Sympathetic nervous system activity (low-frequency power) was significantly elevated during all sleep stages in ME/CFS patients compared to controls (P<0.001).
Parasympathetic nervous system activity (high-frequency power) was significantly reduced specifically during deep sleep (stage N3) in ME/CFS patients (P<0.0001).
ME/CFS patients showed higher nocturnal systolic and mean blood pressure but lower resting heart rates than controls (P<0.0001).
During wakefulness, sympathetic activity was paradoxically lower in ME/CFS patients (P<0.05).
Sleep stage distributions were similar between groups, indicating ANS dysfunction occurs despite normal sleep architecture.
Inferred Conclusions
ME/CFS is characterized by nocturnal cardiac autonomic nervous system dysfunction, specifically lower parasympathetic tone during deep sleep and persistently elevated sympathetic tone during sleep.
The abnormal autonomic balance during sleep may contribute to the cardinal symptom of unrefreshing sleep in ME/CFS patients.
The reversal of autonomic patterns between sleep and wake suggests dysregulation of the normal circadian autonomic cycle in ME/CFS.
Remaining Questions
Does correcting or modulating this ANS dysfunction improve sleep quality and fatigue symptoms in ME/CFS patients?
What This Study Does Not Prove
This small case series (n=8 per group) cannot establish whether ANS dysfunction causes unrefreshing sleep or results from it. The study does not prove that correcting these ANS abnormalities would improve sleep quality or fatigue. Additionally, it does not determine whether these findings apply broadly to all ME/CFS patients, as generalizability is limited by the small, age-restricted sample and lack of standardized control group definitions.