Jun Kohyama

Parental Behaviors and Sleep Outcomes in Infants and Toddlers: A Cross-Cultural Comparison

BACKGROUND To assess the prevalence of parental behaviors and other factors of sleep ecology and to analyze their relationships with sleep outcomes in a large sample of children ages birth to 36months in multiple countries/regions. METHODS Parents of 29,287 infants and toddlers (48% boys; Australia, Canada, China, Hong Kong, India, Indonesia, Korea, Japan, Malaysia, New Zealand, Philippines, Singapore, Taiwan, Thailand, United Kingdom, United States, and Vietnam) completed an internet-based expanded version of the Brief Infant Sleep Questionnaire. RESULTS Overall, there is a high level of parental involvement in sleep onset and sleep maintenance for young children, with significant differences in parenting behaviors across cultural groups. For predominantly-Caucasian, the most common behavior occurring at bedtime is falling asleep independently in own crib/bed (57%), compared to just 4% of those children living in predominantly-Asian regions. Parental behaviors and sleep ecology, including parental presence at sleep onset, bedtime, and bedtime routine, significantly explain a portion of the variance in sleep patterns. Overall, parental behaviors are more highly predictive of nighttime sleep outcomes in predominantly-Caucasian regions. Finally, parental involvement in sleep onset mediates the relationship between cosleeping and sleep outcomes. CONCLUSIONS Overall, the best predictors of nighttime sleep are related to parental behaviors at bedtime and during the night. Furthermore, sleep disruption and decreased total sleep associated with bed sharing and room sharing are mediated by parental presence at bedtime. These findings provide additional support for addressing parental behaviors in behavioral interventions for infant and toddler sleep problems.

Blood pressure in sleep disordered breathing

Aims: To investigate blood pressure (BP) in children with sleep disordered breathing (SDB). Methods: BP was measured during single night polysomnography in 23 suspected SDB child patients with adenotonsillar hypertrophy, but without respiratory or heart failure, or coma. The age related changes of the observed BP were normalised to the BP index. The BP indices were examined in relation to SDB measures, such as the desaturation time (percentage of time with oxygen saturation (SaO2) <90% against the total sleep time), SaO2 nadir, apnoea-hypopnoea index (AHI), and arousal index, in addition to age and body mass index (BMI). Results: The systolic BP index during rapid eye movement sleep (REMS) tended to correlate with AHI, while the diastolic index during REM sleep showed a significant correlation with AHI. The BP indices during non-REMS and wakefulness showed no correlation with the parameters obtained. Patients with an AHI of 10 or more (n = 7, AHIhigh) had significantly higher systolic and diastolic BP indices during both wakefulness and REMS, compared with those with an AHI of less than 10 (n = 16, AHIlow). Two patients in AHIhigh showed no sleep related dip of diastolic BP, and three patients in AHIlow lacked the sleep related dip in systolic BP. By means of multiple regression analysis, age, BMI, and AHI were found to be significant predictor variables of the systolic BP index during REMS. Conclusions: BP in paediatric SDB patients is positively correlated with the degree of SDB.

Rhythmic movement disorder: polysomnographic study and summary of reported cases

Rhythmic movement disorder (RMD) is classified as a sleep-wake transition disorder. However, some RMD patients show rhythmic movements during rapid-eye-movement (REM) sleep, during which muscle activity is completely absent. In order to determine the sleep stages in which episodes of RMD occur, we investigated two children with RMD by means of polysomnography, and also summarized the polysomnographic reports on patients with RMD. We also quantified the REM sleep atonia in our patients using the tonic and phasic inhibition indices (TII and PII). In addition, to examine the involvement of the basal ganglia in RMD patients, we studied the frequency of gross movements (GMs) during sleep in each sleep stage. Both patients showed rhythmic movements in all sleep stages, i.e. including REM sleep. Few rhythmic movements occurred during sleep-wake transition periods. Both patients showed normal TII and PII scores as well as a normal pattern for the sleep stage-dependent modulation of GMs during sleep. Eighteen of the 33 reported RMD patients, including ours, experienced episodes during REM sleep, while the other 15 patients had no episodes during REM sleep. Among the 18 patients who had episodes during REM sleep, eight experienced the episodes exclusively during REM sleep. It is unlikely that the neuronal mechanisms that underlie RMD episodes were the same in the 15 patients who had no RMD episodes during REM sleep and the eight who had them only during REM sleep. We propose that RMD can be divided into several subgroups according to the differences in the underlying neuronal mechanisms.

A newly proposed disease condition produced by light exposure during night: Asynchronization

The bedtime of preschoolers/pupils/students in Japan has become progressively later with the result sleep duration has become progressively shorter. With these changes, more than half of the preschoolers/pupils/students in Japan recently have complained of daytime sleepiness, while approximately one quarter of junior and senior high school students in Japan reportedly suffer from insomnia. These preschoolers/pupils/students may be suffering from behaviorally induced insufficient sleep syndrome due to inadequate sleep hygiene. If this diagnosis is correct, they should be free from these complaints after obtaining sufficient sleep by avoiding inadequate sleep hygiene. However, such a therapeutic approach often fails. Although social factors are often involved in these sleep disturbances, a novel clinical notion--asynchronization--can further a deeper understanding of the pathophysiology of these disturbances. The essence of asynchronization is a disturbance in various aspects (e.g., cycle, amplitude, phase and interrelationship) of the biological rhythms that normally exhibit circadian oscillation, presumably involving decreased activity of the serotonergic system. The major trigger of asynchronization is hypothesized to be a combination of light exposure during the night and a lack of light exposure in the morning. In addition to basic principles of morning light and an avoidance of nocturnal light exposure, presumable potential therapeutic approaches for asynchronization involve both conventional ones (light therapy, medications (hypnotics, antidepressants, melatonin, vitamin B12), physical activation, chronotherapy) and alternative ones (kampo, pulse therapy, direct contact, control of the autonomic nervous system, respiration (qigong, tanden breathing), chewing, crawling). A morning-type behavioral preference is described in several of the traditional textbooks for good health. The author recommends a morning-type behavioral lifestyle as a way to reduce behavioral/emotional problems, and to lessen the likelihood of falling into asynchronization.

Sleep education in medical school curriculum: A glimpse across countries

BACKGROUND The objective of this study was to assess the prevalence of education about sleep and sleep disorders in medical school education and to identify barriers to providing such education. METHODS Surveys were sent to 409 medical schools across 12 countries (Australia, India, Indonesia, Japan, Malaysia, New Zealand, Singapore, South Korea, Thailand, United States, Canada and Viet Nam). RESULTS Overall, the response rate was 25.9%, ranging from 0% in some countries (India) to 100% in other countries (New Zealand and Singapore). Overall, the average amount of time spent on sleep education is just under 2.5h, with 27% responding that their medical school provides no sleep education. Three countries (Indonesia, Malaysia, and Viet Nam) provide no education, and only Australia and the United States/Canada provide more than 3h of education. Paediatric topics were covered for a mere 17 min compared to over 2h on adult-related topics. CONCLUSION These results suggest that there continues to be very limited coverage of sleep in medical school education despite an incredible increase in acknowledgement of the importance of sleep and need for recognition of sleep disorders by physicians.

A quantitative assessment of the maturation of phasic motor inhibition during REM sleep

During rapid eye movement (REM) sleep, phasic and further motor inhibition occurs during clusters of REMs besides tonic motor inhibition. We describe the age-related quantitative change of the activity of this REM-related phasic motor inhibition. For this purpose, we introduced the phasic inhibition index (PII). PII is the rate of simultaneous occurrence of bursts of horizontal REMs and phasic mentalis muscle activity during REM sleep. We examined these phasic REM sleep parameters in 87 healthy children from premature babies to preadolescents. The incidence of bursts of REMs showed no age-related change, while that of the phasic mentalis muscle activity increased with age. The simple ratio between the incidence of bursts of REMs and that of phasic mentalis muscle activity showed no significant age-related change, whereas PII decreased rapidly during infancy and reached low constant values thereafter. We concluded that this age-related PII decline reflected the maturation of REM-related phasic motor inhibition. This is the first quantitative description on the development of human motor inhibition. Taken with the neuronal basis underlying REM-related phasic motor inhibition, we hypothesize that a PII value is within the normal low range as far as both the rostral pontine tegmentum and the brainstem inhibitory pathways are functionally intact.

Potentially harmful sleep habits of 3-year-old children in Japan.

ABSTRACT. To examine the sleep habits of 3-year-old children, we questioned guardians during a routine health examination for 3-year-old children at a public health center. According to the 1105 questionnaires analyzed, the proportion of children who fell asleep at 10 p.m. or later was 49.6%. The nocturnal sleep onset time was significantly correlated with the wake-up time in the morning and was significantly negatively correlated with the nocturnal sleep duration. The average daily total sleep duration (nocturnal sleep duration + nap duration) of regular nap-takers showed a significant negative correlation with the nocturnal sleep onset time. The average values for height, weight, and body mass index (BMI) were not correlated with the nocturnal sleep onset time. Children who went to sleep later got less sleep than those who went to sleep earlier. Because sleep debt has a harmful impact on older children and adults, late sleep onset may have adverse health consequences in young children.

Developmental changes in phasic sleep parameters as reflections of the brain-stem maturation: polysomnographical examinations of infants, including premature neonates

To gain understanding of brain-stem maturation during the early stages of life, we used polysomnography to examine 32 normal infants aged 33-184 conceptional weeks. Our study focused on the developmental aspects of the phasic sleep parameters, REM density and body movement, and the executive system. REM densities were highest in infants aged 36-38 conceptional weeks. The numbers of gross movements and localized movements (LMs) on chin muscle decreased with age; whereas, those of the twitch movements (TMs) on chin muscle increased. Ratios of the TMs to the total number of LMs and TMs (tentatively designated dissociation indexes because of the close relation between LMs and TMs on surface electromyograms) showed significant increases that paralleled the increase in age. We speculate that the dissociation index is a quantitative reliable sleep parameter which reflects brain-stem maturation.

Give children and adolescents the gift of a good night’s sleep: A call to action

Chronic sleep loss is endemic to children and adolescents throughout the world. Studies indicate that children and adolescents are not getting the sleep they need [1,2]. Additionally, research indicates that sleep disturbances are highly prevalent, with studies indicating that 10–75% of parents of young children report that their child has a sleep problem, 10% of adolescents experience insomnia, and 1–3% have diagnosable obstructive sleep apnea [2–5]. Sleep disturbances are also culturally-specific, with sleep practices and parenting definitions of sleep problems varying widely [3,6].

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.