¹Asia University, Department of Psychology, Taichung, Taiwan, ²National Cheng Kung University Hospital, Dou-Liou Branch, Department of Psychiatry, Yunlin, Taiwan, ³National Cheng Kung University & Hospital, College of Medicine, National Cheng Kung University, Department of Psychiatry, Tainan, Taiwan, ⁴National Cheng Kung University, Institute of Gerontology, College of Medicine, Tainan, Taiwan, ⁵National Cheng Kung University, Department of Psychology, Tainan, Taiwan, ⁶National Yang Ming Chiao Tung University, Department of Psychiatry, Taipei, Taiwan, ⁷Tsaotun Psychiatric Center, Ministry of Health and Welfare, Department of Psychiatry, Nantou, Taiwan

Background: Patients with schizophrenia have been reported to have shortened life expectancy and have also been reported to suffer from comorbidity and diseases, such as cardiovascular disease, which affects their quality of life. Thus, we proposed to explore the correlation between mental cognition and heart rate variability to investigate the effect of chronicity on cardiovascular functions.

Aims & Objectives: Schizophrenia patients' perception, judgment, and coping abilities of stress are affected by the disease. This study aimed to explore the relationship between psychiatric symptoms and heart rate variability in patients with schizophrenia.

Method: We collected 20 participants aged between 29 to 56 years with schizophrenia, who were recruited from the Tsao-Tun Psychiatric Center. The 25 healthy-controlled (HC) participants aged 22 to 60 were recruited from the community. Any participants with other major psychiatric disorders (ex, bipolar disorders, major depressive disorders) or other major neurological-related disorders (ex, dementia, intellectual disability, stroke, epilepsy, etc.) were excluded. All the participants experienced two kinds of stressful situations in sequence, “time-limited mental arithmetic with noisy bell ringing” and “put hands in 5°C cold water,” both for five minutes, and took rest for five minutes after each situation. All the statistics were conducted using IBM SPSS 23.0.

Results: The independent t-test revealed the poor performance of baseline period SDNN (t = 6.94, p < .001), LF (t = 6.79, p < .001), and HF (t = 7.02, p < .001) in the SCZ compared to the HC. A two-factor mixed ANOVA was conducted. Results showed significant main effects of stress period, recovery period, and group on almost all three indices (p < .001), but no significant interactions. When faced with physiological stress stimuli, the sympathetic nervous system of schizophrenia responds more violently than that of HC. Still, the parasympathetic nervous system does not respond to the stimulus to balance the sympathetic nervous system, as HC does. After the stimulation, the parasympathetic nerves of both groups continued to operate to balance the previous stimulation. The sympathetic nerves of schizophrenia still fluctuated violently, while those of HC decreased. In the case of cognitive stress stimulation, schizophrenia did not respond appropriately to stress like HC but instead showed signs of alertness only after the stress was relieved.

Discussion & Conclusions: The autonomic nervous system function of schizophrenia was worse than that of HC, showing signs of premature aging of cardiac function. In response to stress, schizophrenia has difficulty regulating the autonomic nervous system to resist danger, requiring longer time to adjust but still challenging to return to balance. We also found that physiological and cognitive stress affect individuals differently. The impact of physiological stimulation is greater but continues declining steadily. Although the impact of cognitive stimulation is relatively small, the change is more prominent and continues to increase, indicating that cognitive stimulation is more sensitive and accumulated.
In addition to the cognitive function, we must pay attention to the heart condition. In the future, we can focus on stress adaptation, cardiopulmonary function training, and more extensive exploration of cardiac function in other mental illnesses.