The balance of the autonomic nervous system is normal in colicky infants

Excessively crying, hard-to-soothe infants are described as colicky. The self-limiting course of infantile colic during early infancy suggests an etiology of transient developmental dysmaturation. It has been proposed that emotional characteristics such as temperament and self-soothing ability are correlated with the balance of the autonomic nervous system. Heart rate variability (HRV) analysis was used for evaluating the balance of the autonomic nervous system in colicky and control infants during and after the colicky period. HRV analysis was carried out on 12 colicky infants and 14 control infants at the age of 2 mo, and repeated on 10 colicky and 11 normal infants at the age of 7 mo. Measurements were performed during polygraphically confirmed slow-wave sleep (sleep stages 3 and 4). Three HRV frequency bands were defined, including a high (0.2-1.0 Hz), middle (0.12-0.2 Hz) and low (0.025-0.12 Hz) frequency variability. There were no differences between the study groups in any of the three HRV frequency bands analyzed. The high frequency variability increased significantly with age in both study groups (p = 0.009).

The findings suggest that imbalance between the parasympathetic and the sympathetic nervous system is not associated with infantile colic and that, in accordance with previous findings, control of HRV shifts in a parasympathetic direction with increasing age during the first year of life.