Pacifier use modifies infant's cardiac autonomic controls during sleep.

Objective: The risk for sudden infant death (SIDS) was postulated to decrease with the use of a pacifier and by conditions increasing parasympathetic tonus during sleep. We evaluated the influence of a pacifier on cardiac autonomic controls in healthy infants.

Study Design: Thirty-four healthy infants were studied polygraphically during one night: 17 infants regularly used a pacifier during sleep and 17 never used a pacifier. Thumb users or occasional pacifier users were not included in the study. The infants were recorded at a median age of 10 weeks (range 6-18 weeks). Autonomic nervous system (ANS) was evaluated by spectral analysis of the heart rate (HR). The high frequency component of HR spectral analysis reflected parasympathetic tonus and the low frequency on high frequency ratio corresponded to the sympathovagal balance.

Results: Most infants (63.6%) lost their pacifier within 30 min of falling asleep. Sucking periods were associated with increases in cardiac sympathovagal balance. During non-sucking periods, in both REM and NREM sleep, infants using a pacifier were characterized by lower sympathetic activity and higher parasympathetic tonus compared with non-pacifier users.

Conclusions: The use of pacifiers modifies cardiac autonomic controls during both sucking and non-sucking sleep periods. Non-nutritive sucking could regulate autonomic control in infants. These findings could be relevant to mechanisms implicated in the occurrence of sudden infant deaths during sleep.