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.