The autonomic dysfunction in patients with ankylosing spondylitis: a clinical and electrophysiological study

The aim of this study was to determine autonomic nervous system (ANS) functions by using clinical and electrophysiological tests in patients with ankylosing spondylitis (AS). Twenty AS and 20 healthy control subjects were recruited. Demographic data, symptoms related with ANS, and neurological findings were recorded. Clinical measurements including the heart rate variation with deep breathing (HRV), heart rate response to standing (HRS), systolic blood pressure response to standing, and diastolic blood pressure response to isometric exercise were obtained to assess parasympathetic and sympathetic functions of the subjects. The electrophysiological assessments of ANS were performed by sympathetic skin response (SSR) and R–R interval variation (RRIV) measurements for the sympathetic and parasympathetic functions, respectively. Patients with AS were subdivided into two groups depending on the activity of disease. The difference between the groups and relationship between ANS variables and clinical entities were determined. Fifteen male and five female AS patients with a mean age of 38 ± 8.05 years and 14 male and six female healthy control subjects with a mean age of 40 ± 9.8 years were included in the study. All the subjects were totally symptom free for ANS involvement and had normal neurological examination findings. The levels of HRV, HRS, and the mean RRIV values were significantly lower in AS patients than in control subjects. The clinical ANS parameters of the patients having more active disease were lower than in subjects with mild disease in regard to HRV values and SSR amplitudes and higher in regard to SSR latencies. The HRV values were found to be correlated with the mean scores of Bath ankylosing spondylitis disease activity index (BASDAI) and C-reactive protein (CRP) levels, and the mean latencies of SSR were correlated with BASDAI scores and CRP levels. In conclusion, our study indicates a subclinical mainly parasympathetic dysfunction of ANS in patients with AS which can be related with disease activity.