Diurnal Change in Heart Rate Variability in Healthy and Diabetic Subjects

Abstract

We assessed the hourly coefficient of variance of RR intervals (CVRR) in 29 subjects with non-insuiin-dependent diabetes mellitus and 19 age-matched healthy subjects using an ambulatory 24-hour ECG monitoring system. We also evaluated CVRR during 100 beats in both groups in the supine posture at 07:00 and 10:00 in the morning. Hourly CVRR showed an overt diurnal variation in both groups especially in the daytime and at midnight, but was significantly lower (p < 0.05) in diabetic patients. CVRR during resting 100 beats at 07:00 was significantly higher (p < 0.05) than that at 10:00 in both groups. These findings indicate that HRV shows an obvious diurnal variation in both groups. As a steep and marked change occurs in the morning, careful consideration is necessary to assess the test performed for a short time span at random times throughout the day, particularly in the morning. © 1992, The Japanese Society of Internal Medicine. All rights reserved.