Sympathetic nervous system response to orthostatic stress in female patients with rheumatoid arthritis

Sympathoneural and adrenomedullary impairments have been suggested in patients with rheumatoid arthritis (RA). In the present study, sympathoneural and adrenomedullary responses to orthostasis were evaluated in eight female RA patients and in eight matched healthy controls. The testing consisted of sequence of stabilization period in supine position, legs-up position, orthostasis, and supine position. In each body position, blood samples were drawn and ECG was recorded. Plasma levels of epinephrine (EPI), norepinephrine (NE) and neuropeptide Y (NPY) were measured and sympathoneural activity was evaluated by analysis of heart rate variability (HRV). Higher baseline NE levels were found in RA patients (P= 0.034), without any difference in response to orthostasis between the study groups. Levels of EPI tended to be lower in RA patients in base line (P= 0.053) and in response to orthostasis (P= 0.079). The RA and control groups did not differ in NPY levels or in HRV parameters considered to reflect sympathetic activity. A subtle tendency to decreased adrenomedullary reactivity but no evidence for abnormal sympathetic responses to orthostasis was found in RA females.