Autonomic imbalance during the day in patients with inflammatory bowel disease in remission. Evidence from spectral analysis of heart rate variability over 24 hours

Background Autonomic function in inflammatory bowel disease has not yet been studied by means of analysis of 24-hour heart rate variability. Aim. To measure heart rate variability in inflammatory bowel disease patients in remission. Patients and methods. Study population comprised 27 patients with inflammatory bowel disease in remission and 28 healthy, sex- and age-matched controls. Two frequency ranges were analysed: low frequency (0.06-0.15 Hz) and high frequency (0.15-0.40 Hz). Results. Mean values of low frequency and low frequency/high frequency ratio were lower in patients than in controls (p<0.001). High frequency in patients tended to be higher than in controls (p=0.09). The only factor that had a marginal effect on heart rate variability indexes was age. In high frequency, there was a significant time effect (p=0.001) for both groups. There was also a significant time effect in low frequency/high frequency ratio in both groups (p<0.001). During daytime, the mean values in low frequency/high frequency ratio were lower in patients than in controls (p<0.001). Conclusions. There is a shift in the autonomic balance in patients with inflammatory bowel disease in remission towards a condition of relative parasympathetic predominance, which, in the first place, reflects a sympathetic pullback. This imbalance has a circadian rhythm and it is more pronounced during the day.