Ambient temperature is associated with changes in infants' arousability from sleep.

STUDY OBJECTIVE: To evaluate the influence of ambient temperature on infants' arousability from sleep. DESIGN: Two groups of healthy infants with a median age of 11 weeks were recorded polygraphically during one night: 31 infants were studied at 24 degreesC and 31 infants at 28 degreesC. To determine their arousal thresholds, the infants were exposed to white noises of increasing intensities during REM and NREM sleep. Arousal thresholds were defined by the auditory stimuli needed to induce arousals. SETTING: N/A. PATIENTS OR PARTICIPANTS: N/A. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: The arousal thresholds decreased across the night in the infants sleeping at 24 degreesC (p=.017). The finding was not found for the infants sleeping at 28 degreesC. When analyzing the arousal responses according to time of the night, it was found that the auditory thresholds were significantly higher at 28 degreesC than at 24 degreesC between 03:00 hr and 06:00 hr (p=.003). These findings were only seen in REM sleep. CONCLUSION: High ambient temperature could add to the difficulty to arouse from REM sleep in the late hours of the night.

Influence of maternal smoking on autonomic nervous system in healthy infants.

To determine the influence of maternal smoking on autonomic nervous system in healthy infants, 36 infants were recorded polygraphically for one night. Their mothers were defined, according to their smoking frequency during pregnancy, as "nonsmokers" (no cigarettes smoked during pregnancy) or "smokers" (10 or more cigarettes per day). The infants had a median postnatal age of 10.5 wk (range 6 to 16 wk); 18 were born to nonsmokers, and 18 to smokers. During the whole night, spectral analyses of heart rate (HR) were evaluated as a function of sleep stages. Two major peaks were recognizable: a low-frequency component (LF) related to sympathetic and parasympathetic activities and a high-frequency component (HF) reflecting parasympathetic tonus. The ratio of LF/HF powers was calculated as an index of sympathovagal interaction. In REM sleep, "smokers" infants were characterized by significantly lower HF powers and normalized HF powers, and higher LF/HF ratios than "nonsmokers." The finding did not reach statistical significance in NREM sleep. In conclusion, maternal smoking induced changes in autonomic control and maturation in infants. These effects of cigarette smoke exposure can be added to those already reported and offer additional evidence for counseling mothers to stop smoking.