Correlates of SDNN heart rate variability in healthy subjects and subjects with type 2 diabetes mellitus

Abstract

Introduction: Standard deviation of R-R intervals (SDNN) predicts mortality in variety of clinical conditions. But little is known about correlates of SDNN. Objective: To investigate correlates of SDNN in healthy subjects and with type 2 diabetes. Materials and Methods: 115 male subjects with type 2 diabetes and 87 controls were studied. In them heart rate (HR), blood pressure (BP), body mass index (BMI), Q -Tc and SDNN were measured. Pearson correlation coefficient and unpaired t test were used for data analysis. P < 0.05 was considered significant. Results: In controls, SDNN was negatively correlating with age and HR (p < 0.05, <0.001 respectively). In subjects with type 2 diabetes, SDNN was negatively correlating with HR, diastolic blood pressure, Q-Tc and duration of diabetes (p < 0.0001, < 0.01, = 0.014, < 0.05 respectively); and was positively correlating with BMI (p < 0.05). Conclusion: Higher HR, DBP, prolonged Q-T interval and duration of diabetes are associated with reduced SDNN in subjects with type 2 diabetes. In them BMI could be a confounding factor while assessing cardiac autonomic dysfunction employing SDNN. In healthy subjects high HR and age are associated with reduced SDNN.