Objective: To investigate sympathetic (SNS) and parasympathetic (PNS) nervous system activity in patients with recently diagnosed rheumatoid arthritis (RA), and to analyze the association between activity of these systems and disease activity, and complaints that frequently occur in RA, viz., pain, fatigue, negative mood, and stiffness.
Methods: To assess sympathetic and parasympathetic nervous activity, the Pre-Ejection-Period (PEP) and Respiratory Sinus arrhythmia (RSA) were measured on two consecutive nights in a real-life environment in 25 patients with RA [19 female (f), 6 male (m), mean age 55.2 years) and 28 healthy controls (20f, 8m, mean age 55.8 years].
Results: Patients showed a significantly shorter PEP (reflecting elevated SNS activity) compared to healthy controls, an effect that was most pronounced in those with active disease. RSA and the heart period did not differ between patients and healthy controls. The heart period was significantly associated with stiffness, but neither PEP nor RSA were associated with pain, fatigue, mood, or stiffness.
Conclusion: Our study showed that cardiac sympathetic nervous system activity is elevated in RA, whereas cardiac parasympathetic activity remains at a normal level. Our results suggest that inflammatory stress rather than the common symptoms of RA challenge the SNS.