Eleen Schupp1, Catharina E. Jansen2, Rinke Stienstra1,3, Cees J. Tack1, Judith L. Bonnes2, Rick I. Meijer1
1 Department of Internal Medicine, Radboudumc, Nijmegen, Netherlands
2 Department of Cardiology, Radboudumc, Nijmegen, Netherlands
3 Division of Human Nutrition and Health, Wageningen University, Wageningen, Netherlands
Eleen.Schupp@radboudumc.nl
Background: Cardiac autonomic neuropathy (CAN) is a complication of type 1 diabetes (T1D) and is associated with increased mortality. Reduced heart rate variability (HRV) is an early sign of CAN. Increased glycaemic variability (GV) has been associated with diabetes complications, including CAN, yet its impact on HRV is unknown. This study aimed to determine the relationship between GV and HRV in people with T1D.
Methods: In this cross-sectional study, daily GV metrics (standard deviation (SD), coefficient of variation (CV) and glycaemic variability percentage (GVP)) were calculated from continuous glucose monitor data in 30 participants with T1D. Participants wore a photoplethysmography wristband for one week, from which daily time domain (standard deviation of RR-intervals (SDNN), root mean square of successive differences of RR-intervals (RMSSD) and percentage of successive differences of RR-intervals that differ by more than 50 ms (pNN50)) and frequency domain (low frequency (LF) power (0.04-0.15 Hz), high frequency (HF) power (0.15-0.40 Hz) and LF/HF ratio) HRV metrics were determined. Linear mixed effects models were used to assess associations between GV and HRV metrics.
Results: Participants had a median age of 62 [50.5-68.3] yrs, median diabetes duration of 35 [16.5-45.3] yrs, and 50% were women. Seven participants had diabetic neuropathy, but none had CAN. In the time domain, SD was inversely correlated with RMSSD (r=-0.22, p<0.001) and pNN50 (r=-0.15, p=0.02), while CV was inversely correlated with RMSSD (r=-0.23, p<0.001) and pNN50 (r=-0.18, p=0.004). In the frequency domain, SD was inversely correlated with LF power (r=-0.14, p=0.03). Other correlations were not significant.
Conclusion: This study shows a weak inverse relationship between GV and HRV in people with T1D. Decreased HRV metrics could be an early sign of CAN. Further research should focus on the cause and effect of long-term relationships between GV and HRV, and cardiovascular complication risk.