Autonomic functions and their relations with disease activity in ankylosing spondylitis

Objectives: To evaluate the autonomic functions in patientswith ankylosing spondylitis (AS) by means ofclinical and electrophysiological tests, to compare thedata with those of healthy individuals and to investigatethe relationship with the disease activity.Patients and methods: 32 asymptomatic AS patientsand 30 healthy controls were included in the study.Parasympathetic functions were evaluated clinicallywith heart rate variability (HRV) and electrophysiologi -cally with R-R interval variation (RRIV). Sympatheticfunctions were evaluated clinically with diastolic bloodpressure response to isometric exercise (DBP) and electrophysiologicallywith sympathetic skin response(SSR). Bath Ankylosing Spondylitis Disease Activity Index(BASDAI) and Ankylosing Spondylitis Disease Acti -vity Score –C (ASDAS-C) were used to estimate the di -sease activity.Results: HRV and RRIV was significantly lower in patientswith AS when compared to controls, and in patientswith BASDAI≥4 when compared to the patientswith BASDAI<4. There was no difference between theAS and the control groups and between the groups withBASDAI≥4 and BASDAI<4 for DBP. Although there wasno difference for SSR between AS and the control groups,SSR latency was significantly longer and SSR amplitudewas significantly smaller in the group with BASDAI≥4when compared to the group with BASDAI<4.Conclusions: Our results indicate a parasympatheticdysfunction in AS patients, however the sympatheticsystem seems to be affected when the disease activity isincreased. Patients with AS even they are asymptoma -tic must be investigated for autonomic dysfunction.