Heart Rate Variability and Metabolic Syndrome in Hospitalized Patients with Schizophrenia

Abstract

Purpose: Reduced heart rate variability significantly increases cardiovascular mortality. Metabolic syndrome increases the cardiac autonomic dysfunction. Recently, increasing cardiovascular mortality has been reported in patients with schizophrenia. This study was done to compare heart rate variability between adults with and without schizophrenia and to compare the relationship of heart rate variability to metabolic syndrome in hospitalized patients with schizophrenia. Methods: This was a descriptive and correlational study in which 719 adults without schizophrenia and 308 adults with schizophrenia took part between May and June 2008. We measured the following: five-minute heart rate variability; high-frequency, low-frequency, the ratio of low-frequency to high-frequency, and the Standard Deviation of all the normal RR intervals. Data was also collected on metabolic syndrome, abdominal obesity, triglycerides, HDL cholesterol, blood pressure and fasting glucose. Results: The Standard Deviation of all the normal RR intervals values of heart rate variability indices were 1.53±0.18. The low-frequency and high-frequency values of heart rate variability indices were significantly higher in hospitalized patients with schizophrenia (3.89±1.36; 3.80±1.20) than those in the healthy participants (2.20±0.46; 2.10±0.46). There were no significant differences between the schizophrenic patients with and without metabolic syndrome. Conclusion: The results of this study indicate that schizophrenia patients have significantly lower cardiac autonomic control, but they have significantly higher low-frequency and high-frequency values than those of healthy adults. Use of antipsychotic drug may affect the autonomic nervous system in schizophrenic patients. Metabolic syndrome was not associated with cardiac autonomic control in schizophrenia patients.

Heart rate variability and vagal tone in schizophrenia: A review

“…However, cardiac autonomic dysregulation and reduced complexity of heart rate modulation have been found in patients with schizophrenia (Bӓr, Birkhofer et al, 2013;Bӓr, Boettger, Koschke et al, 2007;Boettger et al, 2006;Chang et al, 2009;Kim et al, 2004;Lee et al, 2011). Thus, a pattern of reduced complexity in heart rate fluctuations in schizophrenia suggests that these individuals experience difficulty in adapting their heart rate in response to environmental stimuli (Bӓr, Boettger, Koschke et al, 2007;Chang et al, 2009).…”

“…For example, Ieda et al (2014) specifically screened out any drug or alcohol abuse among participants, Lee et al (2011) asked participants to refrain from consuming alcohol for 12 h prior to data collection, and Bӓr et al (2012) controlled for both illegal and legal substances via monitoring serum drug levels. In addition, many HRV research designs have also attempted to match members of the patient and control groups based on smoking habits (Bӓr, Wernich et al, 2008;Bӓr et al, 2012;Berger et al, 2010), requested participants refrain from smoking ranging between 30 min to 6 h before the evaluation (Bӓr et al, 2005;Castro et al, 2008Castro et al, , 2009Chang et al, 2009Chang et al, , 2010Henry et al, 2010;J auregui et al, 2011;Lee et al, 2011;Moon et al, 2013), or both (Bӓr, Boettger, Berger et al, 2007Bӓr, Boettger, Koschke et al, 2007;Bӓr, Koschke et al, 2007;Bӓr et al, 2009). Further, several studies have failed to find that smoking had any statistically significant effect on vagal tone in comparisons between patient and control groups (Birkhofer et al, 2013;Henry et al, 2010;Malaspina et al, 1997).…”

“…In a critical examination of research findings most contradictory with the aforementioned conclusions, the work of Lee et al (2011) is most notable. While this study did identify poorer cardiac autonomic control among schizophrenia patients that is consistent with the findings of previous research, the LF and HF markers of sympathetic and parasympathetic activity were not consistent with the previously described sympathovagal imbalance in schizophrenia.…”

“…While this study did identify poorer cardiac autonomic control among schizophrenia patients that is consistent with the findings of previous research, the LF and HF markers of sympathetic and parasympathetic activity were not consistent with the previously described sympathovagal imbalance in schizophrenia. Specifically, schizophrenia patients examined by Lee et al (2011) demonstrated significantly elevated values of both LF and HF HRV. Although the authors reported that they did not attempt to control for the effect of antipsychotic medication as being a major study limitation, the large sample size of 308 schizophrenia patients nevertheless remains a distinct advantage in its comparison with other similar HRV studies.…”

Comparison of Heart Rate Variability Between Patients With Major Depressive Disorder and Normal Subjects

“…A number of techniques have been developed to quantify beat-to-beat variability in order to provide indices of cardiac autonomic regulation in both health and disease [5]. Depression and mental stress were initially associated with the sympathetic activities and then were found to correlate with parasympathetic activity [6]- [7]. Heart rate seems to be higher while heart rate variability (HRV) tend to be lower in depressed patients [8].…”