Loss of Fractal Heart Rate Dynamics in Depressive Hemodialysis Patients

Objective: To assess the relationship between depression, reduced heart rate (HR) variability, and altered HR dynamics among patients with end-stage renal disease who are receiving hemodialysis (HD) therapy. Methods: We analyzed the 24-hour electrocardiograms of 119 outpatients receiving chronic HD. HR variability was quantified with the standard deviation of normal-to-normal R-R intervals, the triangular index, and the powers of the high- (HF), low- (LF), very-low (VLF), and ultra-low frequency (ULF) components. Nonlinear HR dynamics was assessed with the short-term (1) and long-term (2) scaling exponents of the detrended fluctuation analysis and approximate entropy. The depression level was assessed using the Beck Depression Inventory, Second Edition (BDI-II). HR variability and dynamics measurements were compared by gender, diabetes, and depression with adjustment for age and serum albumin concentration. Results: Most indices of HR variability and dynamics were negatively correlated with age, serum albumin concentration, depression score, and were lower in women and patients with diabetes. The 2 was inversely associated with these variables. Depressed men had significantly lower HF, LF, VLF, and marginally lower ULF than nondepressed persons after adjustment for diabetes and other covariates; no difference in depression was observed in women. The 2 showed marginally significant difference in depression independent from gender and diabetes. Conclusions: Among the patients who received HD, depression is associated with reduced HR variability and loss of fractal HR dynamics. However, the influence of depression on HR variability may vary by gender and physiological backgrounds. Further prospective studies are necessary to confirm their association with poor prognosis. Key words: depression, fractal, heart rate variability, hemodialysis, nonlinear. CHD coronary heart disease; HR heart rate; DFA detrended fluctuation analysis; ApEn approximate entropy; HD hemodialysis; ESRD end-stage renal disease; NKC Nagoya Kidney Center; AMI acute myocardial infarction; ECG electrocardiography; PCR protein catabolic rate; SDNN standard deviation of normal-to-normal R-R intervals; HF high-frequency band; LF low-frequency band; VLF very-low-frequency band; ULF ultra-low-frequency band; SD standard deviation; mNN mean normal-to-normal R-R intervals; BDI Beck Depression Inventory; DSM Diagnostic and Statistical Manual of Mental Disorders; ANCOVA analysis of covariance; GLM general linear model.