Rapid glucose rise reduces heart rate variability in adults with type 1 diabetes: A prospective secondary outcome analysis.

To investigate differences in heart rate variability (HRV) during oral glucose tolerance tests (OGTTs) in response to the rate of change in glucose and to different glycaemic ranges in individuals with type 1 diabetes. This was a single-centre, prospective, secondary outcome analysis in 17 individuals with type 1 diabetes (glycated haemoglobin 53 ± 6.3 mmol/L), who underwent two OGTTs (after 12 and 36 hours of fasting) investigating differences in HRV in response to rapid glucose increases/decreases and different glycaemic ranges during OGTT. Based on the rate of change in glucose level, the variables heart rate (P < 0.001), square root of the mean standard difference of successive R-R intervals (P = 0.002), percentage of pairs of R-R intervals with >50 ms difference (P < 0.001) and corrected QT interval (P = 0.04) were significantly altered, with HRV particularly reduced during episodes of rapid glucose rises. Glycaemic ranges during OGTT had no impact on HRV (P < 0.05). Individuals with type 1 diabetes showed no changes in HRV in response to different glycaemic ranges. HRV was dependent on the rate of change in glucose, especially rapid increases in glucose level.