Autonomic function and nocturnal glycaemic stability
Aims: While autonomic neuropathy is a known complication of diabetes, evidence suggests that autonomic dysfunction might contribute to impaired glucose regulation. This study investigated associations between nocturnal cardiac vagal tone (CVT) and continuous glucose monitoring (CGM) in individuals with and without type 2 diabetes (T2D).
Methods: This cross-sectional study included 40 individuals with T2D and 20 age-matched individuals without diabetes. Participants underwent 72-hour CGM monitoring providing glycaemic variability and time in range, while CVT was derived from nocturnal ECG recordings obtained non-invasively using the ProCVT SmartSheet with integrated ECG sensors. Fifty participants had sufficient paired CVT and CGM data for analysis. Mean nocturnal CVT was analysed continuously and categorised as normal (≥5.0) or poor (<5.0).
Results: Across the combined population, higher nocturnal CVT was associated with lower glucose variability (β=−0.8, p=0.030) and greater time in tight range (β=5.2, p=0.001). In contrast, no significant associations between mean CVT and CGM outcomes were observed in participants with T2D. Periods of poor CVT were followed by a modest 1.9% increase in glucose during the subsequent 15-minute period (p=0.049).
Conclusions: Preserved nocturnal parasympathetic tone was associated with greater glycaemic stability. The authors suggest that parasympathetic dysfunction could contribute to dysglycaemia, potentially creating vicious cycle between dysglycaemia and autonomic dysfunction..
Comments. This study adds to the longstanding discussion of the relationship between autonomic dysfunction and dysglycaemia by examining nocturnal cardiac vagal tone alongside continuous glucose measurement. The association between higher nocturnal CVT and greater glycaemic stability is consistent with the hypothesis that reduced parasympathetic activity may contribute to impaired glucose regulation. Of particular interest is the observation that periods of poor CVT preceded modest increases in glucose, suggesting that short-term changes in parasympathetic activity may be linked to subsequent changes in glucose.
A strength is the simultaneous home-based assessment of nocturnal CVT and glucose over several nights, providing a novel approach to studying autonomic and glycaemic dynamics during sleep. The cross-sectional design of the study does not allow for interpretation of causality. Importantly, the main associations between CVT and CGM outcomes were not observed in participants with T2D, limiting the conclusions that can be drawn regarding the relationship between parasympathetic dysfunction and glycaemic regulation in diabetes.
As all participants with T2D received glucose-lowering treatment, the relationship between parasympathetic function and glycaemic regulation may have been influenced by treatment. It could therefore be interesting to investigate this relationship earlier in the course of dysglycaemia, including in individuals with prediabetes. Furthermore, autonomic activity varies across sleep stages, and concurrent EEG assessment could help determine whether transient changes in CVT reflect psychological changes during sleep or altered autonomic regulation. This may be particularly relevant in T2D, where sleep disturbances, including obstructive sleep apnoea, are common. Future longitudinal studies incorporating measures of sleep quality and sleep-disordered breathing could provide further insight into how changes in parasympathetic function relate to changes in glycaemic regulation over time.
Mette Krabsmark Borbjerg
Reference. Bitsch Poulsen M, Lebech Cichosz S, Julu P, Røikjer J, Mohr Drewes A, Brock C. Preserved cardiac vagal tone is associated with nocturnal glycaemic stability. Diabetologia. 2026 Sep 9. doi: 10.1007/s00125-026-06844-w. Epub ahead of print. PMID: 42714564.
