Correlation of Heart Rate Variability and Inflammatory Markers in Patients with Depression: A Cross-sectional Study

Abstract

Introduction: Depression has been found to be associated with cardiovascular morbidity and mortality. Autonomic dysregulation and inflammation have been implicated as the possible mechanisms. A cross-talk between the autonomic nervous system and inflammatory pathways has been observed in different clinical studies. Aim: To examine the inter-relationship between Heart Rate Variability (HRV), a measure of autonomic function, and inflammatory biomarkers measured by high sensitivity C-Reactive Protein (hsCRP) and Interleukin-6 (IL-6) in patients with depression, without any co-morbid conditions. Materials and Methods: This cross-sectional study was conducted in Department of Physiology, in collaboration with the Department of Psychiatry and Biochemistry, Lady Hardinge Medical College, New Delhi, India, from November 2010 to March 2012. Total 30 drug naive cases (without any comorbid diseases) diagnosed with depression (mild, moderate and severe depression) as per International classification of diseases-10 (ICD-10) guidelines, in the age group of 20- 45 years old were included in the study. Heart rate variability measures were recorded and analysed, frequency domain measures Low Frequency (LF), High Frequency (HF) and time domain measures like Standard Deviation of all NN interval (SDNN) and Root Mean Square of Successive differences of NN intervals (RMSSD). The IL-6 and hsCRP levels were also measured and severity of depression by Hamilton Depression Rating Scale (HDRS) was also assessed and correlated. Data was analysed using the Statistical Package for Social Sciences (SPSS) version 16.0. Normality of data was assessed using the Shapiro-Wilk test. Results: The mean age of the cases was 30.33±6.97 years. There were 14 males and 16 females. There was no significant correlation found between the HRV measures and inflammatory biomarkers (LF vs hsCRP: p-value=0.781, HF vs hsCRP: p-value=0.713, SDNN vs hsCRP: p-value=0.262, RMSSD vs hsCRP: p-value=0.50, LF vs IL-6: p-value=0.477, HF vs IL-6: p-value=0.425, SDNN vs IL-6: p-value=0.137, RMSSD vs IL-6: p-value=0.328). Correlation of HDRS with HRV measures or inflammatory markers was not found to be significant. Conclusion: Future studies with larger sample size and wide array of inflammatory biomarkers besides IL-6 and hsCRP is warranted. No significant correlation was observed between