Michio Fukumizu

Sleep-Related Nighttime Crying (Yonaki) in Japan: A Community-Based Study

Objective. To examine factors associated with the phenomenon of yonaki, or sleep-related nighttime crying (SRNC), in Japanese children Methods. A cross-sectional design incorporating parental self-report was used to investigate relationships between developmental, psychologic, and constitutional/physiological factors in the incidence of SRNC. Participants were the parents of 170 infants, 174 toddlers, and 137 children at a well-infant clinic in Tokyo, Japan. Results. The lifetime incidence rates of SRNC were 18.8% (infants), 64.9% (toddlers), and 59.9% (children). At all ages, children were most likely to cosleep with their parents; however, infants with reported SRNC were found to cosleep more frequently, whereas infants without SRNC were more likely to sleep in separate, child-dedicated beds. Toddlers with frequent SRNC were more likely to have irregular bedtimes and to have nonparental day care than were those without SRNC. Preschoolers who typically slept 9.5 to 10.5 hours per night were less likely to report SRNC than were children with longer or shorter nighttime sleep durations. In all groups, children with frequent SRNC were more likely to suffer from chronic eczema, and toddlers and preschoolers with SRNC exhibited bruxism more frequently. Conclusions. The traditional Japanese arrangement of cosleeping represents an environment in which parents are readily accessible to children during waking episodes. Physical proximity to the parents in infancy, but not at other ages, is associated with SRNC. The higher incidence of bruxism, chronic eczema, and day care use among children with frequent SRNC supports the hypothesis that nighttime anxiety may promote SRNC.

Central respiratory pauses, sighs, and gross body movements during sleep in children

Sighs (SIs) and gross body movements (GMs) during sleep are common spontaneous, arousal behaviors during sleep. These physiological behaviors either precede or follow central respiratory pauses (CPs) during sleep in normal subjects. However, little attention has been paid to the temporal relationships between CPs and spontaneous behaviors except in early infancy. In the present study, the age- and state-related changes in the frequency and duration of apnea-behavior relationships were studied cross-sectionally in 19 healthy children aged between 3 months and 7 years of age. CPs, SIs, and GMs were assessed in a single all-night polysomnography and respiratory inductive plethysmography. We divided the data into two age groups: less and more than 15 months of age. The results showed that frequency of CPs > or = 10 s increased with age, while the frequency of GMs and SIs decreased. Isolated CPs appeared more frequently during rapid-eye-movement sleep (REMS) than during nonrapid-eye-movement sleep (NREMS). The frequency of both SIs and GMs that appeared after CPs was higher during REMS than during NREMS. The sum of CPs preceded by SI, and CPs preceded by GM accounted for about 75% of all central apnea events. These two events appeared more frequently during NREMS than during REMS and the duration of both events in NREMS increased significantly with age. During NREMS, few and delayed behaviors thought to restart respiration after CPs have been described. Future work should examine developmental differences in the occurrence of physiological behaviors in relation to CP in NREMS and REMS.

Sleep fragmentation and evidence for sleep debt in alcohol-exposed infants

BACKGROUND Infants exposed prenatally to alcohol are at increased risk for poor neurodevelopmental outcome including Sudden Infant Death Syndrome. AIM To examine the relationship between prenatal alcohol exposure, sleep, arousal and sleep-related spontaneous motor movements in early infancy. STUDY DESIGN Low-income women (N=13) were interviewed regarding pre- and pregnancy rates of alcohol, cigarette smoking and other substance use in the perinatal period. Infants were examined in a laboratory nap study using EEG, videography and actigraphy at 6-8 weeks of age. Estimates of maternal pre- and pregnancy alcohol use were used to divide infants into high vs. low maternal alcohol use groups. SUBJECTS Mother-infant dyads recruited from a family practice clinic. OUTCOME MEASURES Sleep-related spontaneous movements, behavioral state, and maternal assessments of infant alertness and irritability. RESULTS Pre-pregnancy rates of alcohol consumption including binge drinking correlated with maternal report of poor infant alertness, and increased irritability. High maternal exposure groups showed increased sleep fragmentation, e.g., frequency and duration of wakefulness following sleep onset and decreased active sleep. Bout analysis of the temporal structure of sleep-related spontaneous movements showed significantly reduced bout duration associated with high maternal alcohol use. CONCLUSION These results present evidence that prenatal alcohol exposure disrupts postnatal sleep organization and suppresses spontaneous movements during sleep, and increased sleep fragmentation promotes sleep deprivation. Results are consistent with the SIDS model of chronic sleep debt and suggest that attenuated sleep-related movements should be examined as an important modulator of cardiorespiratory functions during sleep in high-risk groups.

Apneic preterms and methylxanthines: Arousal deficits, sleep fragmentation and suppressed spontaneous movements

Objective:To determine if apneic preterm infants currently treated with methylxanthines develop evidence of sleep deprivation from cumulative arousal and motor activational effects.Study Design:Sleep, wake, arousal and actigraphic movements were monitored in extubated clinically stable premature infants (N=37). Neonates were free of other medications for >72 h and were grouped based on methylxanthine exposure: >5 days with caffeine (n=14), >5 days theophylline (n=13) or no prior exposure (n=10).Result:Duration of methylxanthine treatment predicted increased arousals, wakefulness and actigraphic movements, and decreased active sleep. Recording from 1200 to 0500 hours, methylxanthine-treated groups showed reductions in all arousal parameters: waking state, number of wake epochs, brief arousals and composite arousal index, and shorter fast-burst, sleep-related motility than untreated controls.Conclusion:In apneic preterms, chronic methylxanthine treatment appears to produce sleep deprivation secondary to the stimulatory action of methylxanthines on arousal and motor systems.