Autonomic Dysfunction in Chronic Fatigue Syndrome

Symptoms of autonomic dysfunction are one of the characteristic features of the clinical condition known as chronic fatigue syndrome (CFS). In this study we examined the autonomic nerve functions in 1,099 patients with CFS and in 361 normal healthy controls. The autonomic nerve functions were studied in terms of heart rate variability and spectral analysis, and by using the maximal Lyapunov exponent (MLE) and chaotic analysis. The heart rate variability analysis revealed that both the logarithmic low-frequency power (Log LF) and logarithmic high-frequency power (Log HF) were reduced significantly with age in healthy subjects (p < 0.005). When we compared these parameters between the CFS patients and healthy controls according to age groups, there was no significant difference in Log LF between CFS and control except in the case of the 40's age group. However, Log HF decreased significantly in moderate and severe fatigue CFS groups in all age groups. All of the severe fatigue CFS age groups had a significant increase in the ratio of Log LF/HF as compared with that of the healthy controls. When we studied the change in these power values during sleep as compared with that during awake time, the HF power rose 3.03-fold in the controls and 1.86-fold in the CFS group during sleep as compared with that during the awake time; and this difference in fold increase during sleep between the CFS and control groups was significant (p < 0.05). Furthermore, the MLE for both the moderate and severe fatigue CFS groups was decreased significantly as compared with that of the healthy control group (p < 0.01). It is well known that autonomic nervous function differs greatly in individuals, but our present large research study indicates that there is no doubt that parasympathetic nervous dysfunction is involved in the pathophysiology of CFS patients with severe fatigue. We incorporated the evaluation of autonomic function into the Japanese CFS diagnostic criteria in 2012, because this evaluation might be a useful objective diagnostic tool for CFS.