Effect of excessive infant crying on resting BP, HRV and cardiac autonomic control in childhood.

Objective: Early life stress has been shown to influence the developing autonomic nervous system. Stressors in infancy may program the autonomic nervous system resting state set point, affecting cardiovascular function in later life. Excessive crying may be an indicator of increased stress arousal in infancy. We hypothesized that excessive infant crying is related to altered cardiac autonomic nervous system activity and increased blood pressure at age 5-6 years.

Methods: In the Amsterdam Born Children and their Development study, excessive crying, maternal burden of infant care and maternal aggressive behavior in the 13th week after birth (range 11-16 weeks) were reported using questionnaires. Blood pressure, heart rate, heart rate variability and indicators of cardiac autonomic nervous system activity (sympathetic drive by pre-ejection period, parasympathetic drive by respiratory sinus arrhythmia) were measured at age 5-6 years during rest. Inclusion criteria were singleton birth, term-born, and no reported congenital or cardiovascular problems (N = 2153 included).

Results: Excessive crying (2.8%) was not associated with resting heart rate, heart rate variability, pre-ejection period, respiratory sinus arrhythmia nor with blood pressure at age 5-6 years.

Conclusions: Excessive infant crying as an indicator of increased stress arousal does not seem to be related to resting activity of the autonomic nervous system or blood pressure at age 5-6. Potential associations may become visible under stressed conditions.