Rationale. The sleep-related factors that modulate the nocturnal worsening of asthma in children are poorly understood. This study addressed the hypothesis that asthmatic children have a REM sleep-related vulnerability trait that is independent of OSA. Methods. We conducted a retrospective cross-sectional analysis of pulse-oximetry signals obtained during REM and NREM sleep in control and asthmatic children ( ). Asthma classification was based on preestablished clinical criteria. Multivariate linear regression model was built to control for potential confounders (significance level ). Results. Our data demonstrated that (1) baseline nocturnal respiratory parameters were not significantly different in asthmatic versus control children, (2) the maximal % of SaO2 desaturation during REM, but not during NREM, was significantly higher in asthmatic children, and (3) multivariate analysis revealed that the association between asthma and REM-related maximal % SaO2 desaturation was independent of demographic variables. Conclusion. These results demonstrate that children with asthma have a REM-related vulnerability trait that impacts oxygenation independently of OSA. Further research is needed to delineate the REM sleep neurobiological mechanisms that modulate the phenotypical expression of nocturnal asthma in children. 1. Introduction Asthma is a chronic inflammatory disease characterized by worsening of symptoms during sleep [1, 2]. This nocturnal vulnerability of asthmatic individuals has been previously attributed to increased vagal tone, decreased sympathetic activity, reduced functional residual capacity of the lungs (affecting the small airways), endogenous circadian system changes during the night, and a higher risk for obstructive sleep apnea (OSA) in the asthmatic population [2–4]. Interestingly, several studies have reported that asthmatic patients deteriorate more during the morning hours with the majority of respiratory arrests and sudden deaths occurring from midnight to 8 am [5, 6]. The latter phenomenon suggests a greater influence of the rapid eye movement (REM) sleep in the asthmatic condition since this sleep stage predominates during the second part of the night [7]. REM sleep is considered particularly important in the pathogenesis of OSA and other sleep-related breathing abnormalities [8–12]. It has also been suggested that REM sleep is characterized by nocturnal bronchoconstriction [13]. In the context of pediatric asthma, we have recently identified that asthmatic children with OSA have more REM sleep-related breathing abnormalities
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