[Phasic activity of REM sleep in newborns and infants and its relationship with apnea episodes]

When the apnea hypothesis turned to be an explanation for sudden infant death syndrome (SIDS) many authors tried to find if near-miss or apparent life-threatening events (ALTE) could be markers of SIDS. It was suggested that phasic REM activity is associated with increased respiratory neuron activity and prevents prolonged apnea in near-miss SIDS. In a previous retrospective study with newborns we did not confirm these results, nevertheless we had several babies with serious neurological disturbances. The aim of this study was to verify the relationship of phasic activity (rapid eyes movement and sucking bursts) with both apneic and non-apneic epochs during REM sleep. We studied 86 children referred for evaluation because they presented an ALTE during sleep or apneas. The subjects were divided in three groups by age (newborns, n = 31; 1-6 months, n = 48; and > 6 < 12 months, n = 7). They were all submitted to a clinical and neurological evaluation in order to detect possible etiological factors to the apneic episode. The polysomnograms (PS) consisted of EEG, submental EMG, electro-oculogram and cardiorespiratory monitoring. The records were made between 11 am and 15 pm for 2 or 3 hours. The electrodes were disposed in the 10-20 system. During one five-minutes epoch of REM sleep we verified the incidence of phasic activity (rapid eyes movement or sucking bursts) time locked to apneic episodes and compared with a similar duration non-apneic epoch. To evaluate the relationship of phasic activity with apneic and non-apneic eopchs we compared the incidence of rapid eyes movements and sucking bursts in each group. Our results showed that phasic activity of REM sleep (sucking bursts) seems to be more frequent in newborns in non-apneic epochs (p < 0.05). Between 1-6 months the number of rapid eyes movements were more frequent in non-apneic epochs (p = 0.001). In conclusion our findings suggest that phasic activity of REM sleep seems to be more evident in nonapneic epochs during the first six months of life. Although central apneas may have their origin in an intrinsic disturb of the respiratory control center they may be influenced by the phasic activity of REM sleep. The rapid eyes movements and sucking bursts may have a protection effect against apneas at least in the first 6 months of life. which is the predominant period for SIDS. We suggest that the excitatory driving related to generation of phasic activity in REM sleep may block or atenuate tonic inhibition of respiratory motoneuron and avoid apnea. It is still open for discussion the possible relation between failure of this protective mechanism and SIDS.