Study Of Heart Rate Variability Of Schizophrenia Patients Based On Autonomic Nervous Tests

Schizophrenia is a kind of typical and serious mental disorder.The clinical diagnosis and evaluation of schizophrenia are dependent on the experience of physician and the judgement of patients,which may lead a misdiagnosis or a missed diagnosis.Therefore,it’s critical to develop an objective physiological index which can be applied to the diagnosis of schizophrenia.In recent years,several studies have used heart rate variability(HRV)to study the autonomic nervous system(ANS)of schizophrenia patients,and found that the autonomic nervous function of schizophrenia patients is significantly different from that of normal controls.However,most previous analyses for schizophrenia patients are based on the heart rate variability parameters in a resting state.The single research state and method cannot provide individual levels of assessment and prediction.Based on the autonomic nervous tests with stimulation effects of physiological and psychological environmental stress,in this study,the changes of ANS of schizophrenia patients were analyzed,and the clinical application of heart rate variability parameters was systematically discussed.The main contents of this thesis are as follows:1)In this study,45 schizophrenia patients and 45 normal controls were recruited,and their electrocardiogram signals during the autonomic nervous tests including rest state,mental arithmetic state,deep breathing state and recovery state were acquired.An adaptive threshold algorithm was used to extract heart rate variability from the electrocardiogram signals after filtering processing.The parameters of the time domain,frequency domain,and nonlinear dynamics of HRV were calculated.2)The differences between schizophrenia patients and normal controls were compared.The correlations between heart rate variability and Positive and Negative syndrome scales scores of schizophrenia patients were calculated.The results showed that the HRV of schizophrenia patients was decreased,which indicated increased sympathetic activity and reduced parasympathetic activity.The ANS of schizophrenia patients arose prolonged stress activation after the cessation of stimulation test,which indicated a decreased ability of schizophrenia patients to recover from stress-induced events.The results of correlation analysis showed that most features of heart rate variability were related to the severity of clinical symptoms,partial correlation coefficient reached 0.5～0.6,and the more severe the clinical symptoms of schizophrenia,the greater the differences in heart rate variability.3)Based on the differences of HRV between schizophrenia patients and normal controls,we applied a machine learning algorithm of support vector machine(SVM)to classify patients and normal controls using the parameters of HRV under the autonomic nervous tests.The classification results indicated that the HRV during a series of autonomic nervous test achieved the best performance which classification accuracy,sensitivity and specificity reached 85% compared to any single test.The primarily contributed parameters were CR,Ap En,SD2 and HF.Based on the features of HRV under a series of autonomic nervous tests,the differences of autonomic nervous function between schizophrenia patients and normal controls were analyzed in this study.A machine learning algorithm of SVM achieved the best performance of the discrimination between schizophrenia patients and normal controls.The results suggest that the autonomic nervous function of schizophrenia patients might be dysfunctional,especially in the environmental pressures.The HRV is a convenient and economical physiological index,which can reflect the state of autonomic nervous function objectively,and can be used for early diagnosis for schizophrenia.