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STUDY OBJECTIVES A deficit in arousal process has been implicated as a mechanism of sudden infant death syndrome (SIDS). Compared with control infants, SIDS victims showed significantly more subcortical activations and fewer cortical arousals than matched control infants. Apparent life-threatening event (ALTE) is often considered as an aborted SIDS event. The aim of this study was to study the arousal characteristics of ALTE infants during the first months of life. DESIGN 35 ALTE infants were studied with nighttime polysomnography at 2-3, 5-6, and 8-9 months of age. Eighteen of the infants had mothers who smoked. The infants were born full term and were usually supine sleepers. Sleep state and cardiorespiratory parameters were scored according to recommended criteria. Arousals were differentiated into subcortical activations or cortical arousals, according to the presence of autonomic and/or electroencephalographic changes. The results were compared with those of 19 healthy infants with nonsmoking mothers. RESULTS During NREM sleep, the ALTE infants had fewer total arousals, cortical arousals, and subcortical activations at 2-3 and 5-6 months (P < 0.001) than control infants. ALTE infants with smoking mothers had more obstructive apnea (P = 0.009) and more subcortical activations during REM sleep at 2-3 months of age (P < 0.001) than ALTE infants with nonsmoking mothers. CONCLUSIONS Spontaneous arousals were differently altered in ALTE infants than in SIDS infants, suggesting an entity different from SIDS. ALTE infants with smoking mothers had arousal and respiratory characteristics that were similar to future SIDS victims, suggesting some common abnormalities in brainstem dysfunction.

International audience; OBJECTIVE: The propensity to arouse from sleep is an integrative part of the sleep structure and can have direct implications in various clinical conditions. This study was conducted to evaluate the maturation of spontaneous arousals during the first year of life in healthy infants. DESIGN: Nineteen infants were studied with nighttime polysomnography on 3 occasions: aged 2 to 3 months, 5 to 6 months, and 8 to 9 months. Ten infants with a median age of 3 weeks were added to the main study to assess the maturation of arousals from birth. The infants were born full-term, were healthy at the time of study, and had no history of apnea. Sleep-state and cardiorespiratory parameters were scored according to recommended criteria. Arousals were differentiated into subcortical activations or cortical arousals, according to the presence of autonomic and/or electroencephalographic changes. Frequencies of subcortical activations and cortical arousals were studied at different ages in both rapid eye movement (REM) and non-rapid eye movement (NREM) sleep. RESULTS: During sleep time, the frequency of total arousals, cortical arousals, and subcortical activations decreased with age. The maturation of the arousal events differed according to sleep states and types of arousals. With age, cortical arousals increased in REM sleep (P = 0.006) and decreased in NREM sleep (P = 0.01). Subcortical activations decreased with age in REM (P < 0.001) and NREM sleep (P < 0.001). CONCLUSIONS: During total sleep time, the frequency of cortical arousals and subcortical activations decreased with maturation. However, the maturation process was different between cortical arousals and subcortical activations. This finding suggests a difference in the maturational sequence of the different brain centers regulating arousals.

Various definitions of arousals have been used in infants. An international group of experts has worked on a consensus for the scoring of arousals in healthy infants, aged between 1 and 6 months. This opinion paper summarizes the consensus statement on the scoring of arousal. The paper reviews recommended techniques for the recording of arousal in infants. Scoring includes the differentiation between subcortical activation, with no visible change n the electroencephalograph (EEG) recording, and cortical arousals associated with EEG changes. The arousals are further scored as spontaneous or induced, according to environmental conditions. Potential limitations to the method are discussed, with the hope that this document could contribute to promote further progresses in the scoring of infants arousals from sleep.