Assessment of Autonomic Function in Patients with Schizophrenia Using Spectral Analysis and Approximate Entropy Method

Objective: Autonomic nervous system involvement in patients with Schizophrenia has rarely been studied and has shown conflicting results. Our main purpose was to demonstrate that the Schizophrenia patients have malfunction in autonomic function compared with another group of normal control subjects by using power spectra of Heart Rate Variability (extracted from ECG) and measuring the frequency gain response of the two groups. Other purpose of this study was to determine wither the duration of Schizophrenia affect of function of Autonomic nervous system using the nonlinear method approximate entropy index (ApEn). Methods: Fifty two patients with Schizophrenia and fifty one matched healthy subjects were evaluated at Neurology Center, Johns Hopkins Hospital, Maryland, USA during 2013/ 2014 by measuring the breathing at different rates and HRV signal derived from Electrocardiogram (ECG). The auto-power and cross power spectra between HRV signal and breathing signal at different breathing rate were calculated and frequency gain response for both groups were obtained. ApEn described as measure of regularity of HRV was calculated for both patients with Schizophrenia and healthy control subjects. Results: Both frequency gain response and ApEn measure were reduced in patients with Schizophrenia in comparison with control group. The power spectra of patients with Schizophrenia showed reduced High Frequency (HF) value and higher low frequency with respect to control subjects. On other hand, ApEn measure was significantly reduced in longer Schizophrenia duration in Patients with Schizophrenia. Conclusion: These findings suggest that the spectral analysis of HRV signal using breathing at different frequencies may detectunbalance of autonomic of autonomic system of patients with Schizophrenia specially with increasing the sympathetic activity (higher low frequency) and reducing the parasympathetic tone (reduced frequency gain response) which indicate malfunction of autonomic function (Deficit) in patients with Schizophrenia. ApEn may be used as marker for screening Schizophrenia patients for the assessment of function of autonomic nervous system related to the duration of the disease.