Maturation of motility and motor inhibition in rapid-eye-movement sleep

Validity of an algorithm for determining sleep/wake states using FS-760 in school-aged children

Background

Actigraphy is a method used for determining sleep (S)/wakefulness (W) by actigraph, a device equipped with a built-in accelerometer and an algorithm validated for each device. The S/W determination algorithm for the waist-worn actigraph FS-760 has been formulated for adults. However, the algorithm for children has not been established. The purpose of this study was to formulate an algorithm for discriminating S/W in school-aged children using FS-760 and to evaluate its validity. We further tested the generalizability of existing algorithm for adults by applying it to the children’s activity data and then examined factors associated with adult algorithm agreement rates by multiple regression analysis using combined adult and children data.

Methods

Sixty-five, healthy, school-aged children (aged 6 to 15 years) were recruited and randomly assigned to two groups: A (n = 33) and B (n = 32). They underwent 8-h polysomnography (PSG) and wore FS-760 simultaneously to obtain activity data. To determine the central epoch of the sleep/wake states (𝑥), a five-order linear discriminant analysis was conducted using the activity intensity of group A for five epochs (𝑥₋₂, 𝑥₋₁, 𝑥, 𝑥₊₁, 𝑥₊₂; 10 min) and evaluate its accuracy with the activity of group B. To reveal the factors associated with adult algorithm agreement rate, we integrated the activity, age, sleep efficiency of 15 adults (aged 20 to 39 years) and those of 65 children for multiple regression analysis.

Results

The mean agreement rate of the developed algorithm was 91.0%, with a mean sensitivity (true sleep detection rate) of 93.0% and a mean specificity (true wakefulness detection rate) of 63.9%. The agreement rate of the adult algorithm applied to children’s activity was significantly lower (81.8%) than that of the children algorithm. Multiple regression analysis showed that the agreement rates calculated by the adult algorithm were significantly related to mean activity of the 𝑥 epoch in NREM and REM sleep as well as age and sleep efficiency.

Conclusions

The S/W states in school-aged children can be reliably assessed using the developed algorithm for waist-worn actigraph FS-760. Since the accuracy of the adult algorithms decreased when applied it to children which have different activity levels during sleep, the establishment and validation of population-specific S/W algorithms should be required.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40101-022-00303-2.

Comorbidities in infants with obstructive sleep apnea

STUDY OBJECTIVE

The clinical characteristics of obstructive sleep apnea (OSA) in infants have been insufficiently characterized. Our aim was to describe identifiable comorbidities in infants with obstructive sleep apnea, which may assist in recognizing these patients earlier in their disease course and help improve management.

METHODS

This was a single-center, retrospective study involving infants 0-17 months of age with a diagnosis of OSA on the basis of clinical features and nocturnal polysomnography (PSG) at the Mayo Clinic Center for Sleep Medicine between 2000 and 2011. Patients were excluded if they had central apnea accounting for greater than 50% of respiratory events. OSA severity was determined by the apnea-hypopnea index (AHI).

RESULTS

One hundred thirty-nine patients were included. Based upon the AHI, they were subdivided into mild (AHI <5; 30%), moderate (AHI 5-9; 30%), or severe (AHI >10; 40%) categories. Comorbidities included gastroesophageal reflux in 95/139 (68%), periodic limb movements in sleep in 59/139 (42%), craniofacial abnormalities in 52/139 (37%), neuromuscular abnormalities in 47/139 (34%), prematurity in 41/139 (29%), genetic syndromes in 41/139 (29%), laryngomalacia / tracheomalacia in 38/139 (27%), and epilepsy in 23/139 (17%) of subjects. Severity of OSA correlated with prematurity, having a genetic syndrome, or neuromuscular abnormality. Multispecialty evaluation was needed for 119/139 (86%).

CONCLUSION

Comorbidities in infants with OSA differ from those of older children. Based upon the comorbidities identified in our study population, it appears that appropriate management of infants with OSA requires a multidisciplinary approach involving genetics, gastroenterology, pulmonology, otolaryngology, neurology, and general pediatrics.

Normative values of polysomnographic parameters in childhood and adolescence: arousal events

OBJECTIVE

This study focused on differences in arousals during sleep, using the arousal rules of the American Academy of Sleep Medicine, by gender, age, and maturity in healthy children.

METHODS

One-night polysomnography was performed on 209 healthy German children (age 1-18 years) at their habitual bedtimes in 16 laboratories. Subjects were grouped by gender (112 females, 97 males), age, and Tanner stage.

RESULTS

Normative values of arousal events in sleep are presented, including indexes of spontaneous and respiratory arousals, total electroencephalogram (EEG) arousals, phasic increase in submental electromyogram (EMG) in stage R, and leg movements. With increasing age, a decrease was seen in: EEG arousal index ≥1-2.9 s, EEG arousal index ≥3 s, index of total EEG arousals, index of respiratory arousals, chin EMG enhancement in stage R ≥1-2.9 and ≥3 s, index of total leg movements, and leg movements with EEG arousals (p<0.05). Only spontaneous arousals showed no association with age. There was a significant negative correlation between Tanner stage and arousals ≥1-2.9 s, respiratory arousals, leg movements, and leg movements with arousals (p<0.05). Only arousals ≥3 s and total leg movements showed gender differences (p<0.05).

CONCLUSIONS

For the diagnosis of pediatric sleep disturbances, the given arousal data enable estimation of the degree of deviation from normal findings for age and maturity. There is need for further research on, and further discussion of, the arousal rules of the American Academy of Sleep Medicine.

Apnea, glial apoptosis and neuronal plasticity in the arousal pathway of victims of SIDS

Of 27,000 infants whose sleep-wake characteristics were studied under the age of 6 months, 38 died unexpectedly 2-12 weeks after the sleep recording in a pediatric sleep laboratory. Of these infants, 26 died of sudden infant death syndrome (SIDS), and 12 of definitely identified causes. The frequency and duration of sleep apneas were analysed. Sleep recordings and brainstem histopathology were studied to elucidate the possible relationship between sleep apnea and neuropathological changes within the arousal system. Immunohistochemical analyses were conducted using tryptophan hydroxylase (TrypH), a serotonin synthesizing enzyme, and growth-associated phosphoprotein 43 (GAP43), a marker of synaptic plasticity. The terminal-deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method was used for apoptosis. The pathological and physiological data were correlated for each infant. In the SIDS victims, statistically significant positive correlations were seen between the number of TrypH-positive neurons in the dorsal raphe nucleus of the midbrain and the duration of central apneas (p = 0.03), between the number of TUNEL-positive glial cells in the pedunculopontine tegmental nucleus (PPTN) and the average number of spines in GAP43-positive neurons in the PPTN (p = 0.04). These findings in the dorsal raphe nucleus of the midbrain and PPTN, that play important roles in the arousal pathway suggest a possible link between changes in arousal and SIDS.

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.

Rapid-eye-movement sleep in jittery infants

BACKGROUND

The pathogenesis of neonatal jitteriness (JT) remains unknown. Neonatal JT could be one of the symptoms associated with drug withdrawal syndrome due to maternal medication. To study the influence of chemicals and environment on brain development in the fetal period, Swaab and Mirmiran proposed "behavioral teratology". JT could be one of the targets for this concept. Swaab and Mirmiran postulated that rapid-eye-movement sleep (REM sleep) is useful for studying behavioral teratology.

AIM

We aimed to determine the neurophysiological alterations in infants with JT by investigating REM sleep.

STUDY DESIGN

Sleep records were obtained three times for each of six jittery infants. The mothers of three infants had been on medication (either alpha-methyl dopa, reserpine or haloperidol) during pregnancy, whereas the mothers of the other three infants took no medication during pregnancy. REM sleep parameters (the amount of REM sleep against the total sleep time, newly designated indices-tonic inhibition index (TII) and phasic inhibition index--, and the incidences of gross movements, phasic chin muscle activity (PCMA), and bursts of rapid eye movements) in the six jittery infants were compared with those in age-matched controls.

RESULTS

Regardless of maternal medication, TIIs, which represent the shortening of PCMA during REM sleep, were higher in the jittery infants than in the controls. No other REM sleep parameters showed constant differences between the patients and controls.

CONCLUSION

Release of the blockade of dopamine D2 receptors in the fetal brain is considered to be critical for the occurrence of neonatal JT with elevation of TII. Since the abnormal elevation of TII continued after 6 months of age when our patients did not show JT anymore, we have to keep monitoring jittery infants from the standpoint of "behavioral teratology".

Disturbance of phasic chin muscle activity during rapid-eye-movement sleep

In patients with Rett syndrome (RS), a peculiar type of disturbance in phasic chin muscle activity during rapid-eye-movement sleep (REMS) (e.g. an elevation of phasic inhibition index (PII) without an affection of tonic inhibition index (TII)) has been reported. The similar disturbance in REMS was reported not only in child patients with infantile spasms, severe myoclonic epilepsy in infancy (SMEI), severe nocturnal enuresis, and autism but also in adult patients with Parkinson's disease (PD). Except for SMEI and PD, patients with the other four clinical entities including RS could express autistic tendency. Since the responsible lesion for the occurrence of an elevation of PII with a normal TII value is likely to be in the pontine tegmentum, this subcortical structure is hypothesized to be involved in the appearance of autistic tendency.

Tonic and phasic inhibition indices are constant among nights: new indices for evaluating the degree of the two types of motor inhibition during REM sleep

BACKGROUND

Tonic inhibition index (TII) and phasic inhibition index (PII) were proposed as indices for evaluating the degree of two types of motor inhibition activity during rapid eye movement (REM) sleep.

METHODS

In the present study, therefore, six healthy men underwent two consecutive all-night polysomnography, and reproducibility of TII and PII was evaluated.

RESULTS

TII was 0.85+/-0.07 (mean+/-SD) on the first night and 0.88+/-0.08 on the second; and PII was 3.4+/-2.1 on the first night and 4.9+/-1.8 on the second. Neither TII nor PII was significantly different between the two nights.

CONCLUSION

One night sleep study is considered sufficient for using TII and PII as a tool for evaluating motor inhibition activity during REM sleep in adults.

REM sleep atonia: responsible brain regions, quantification, and clinical implication

Muscle tone is profoundly suppressed during rapid-eye-movement sleep. Two indices that quantify this muscle activity suppression were introduced: the tonic inhibition index (TII) and the phasic inhibition index (PII). TII expresses the shortening of phasic chin muscle activity, and PII indicates the degrees of suppression of the occurrence of phasic chin muscle activity in the period of the burst of rapid eye movements. TII increased significantly with age, while PII decreased significantly. TII was found to reach the adult level at 12.3 years of age, while PII decreased to the adult value at 0.4 years. According to this difference in age between their maturation, the human nervous systems involved in muscle activity suppression are hypothesized to comprise at least two independent systems. TII and PII are also hypothesized to be affected by the activity of the brainstem inhibitory centers, which might be implicated in the suppression of muscle activity during wakefulness as well.

Development of REM sleep atonia

OBJECTIVES

To study the functional development of neuronal systems that suppress muscle activity, we quantified the chronological change of atonia in rapid-eye-movement sleep (REMS).

METHODS

REMS atonia was quantified by the tonic and phasic inhibition indices (TII and PII). TII indicates the shortness of chin muscle activity, whereas PII standardizes the simultaneous occurrence of chin muscle activity and bursts of rapid eye movements. TII and PII were calculated in REMS of 135 polysomnographical recordings obtained in healthy humans from premature babies to a 77-year-old man.

RESULTS

TII increased significantly with age, while PII decreased significantly. TII reached an adult level at preadolescence, while PII at early infancy.

CONCLUSION

Human nervous systems involved in both tonic and phasic inhibition in REMS raise their activities with age. Since TII and PII reach adult levels at different ages, suppression of muscle activity is hypothesized to be mediated through at least 2 independent systems in humans.

Polysomnographic studies of Lesch-Nyhan syndrome

Three cases of Lesch-Nyhan syndrome (LNS) were examined by polysomnography to assess the brainstem function, and to determine the causes of the neurological manifestations and sudden death in this syndrome. In the two older cases, the amount of slow wave and rapid eye movement (REM) sleep, the REM density and the frequency of REM bursts were decreased. In the youngest case, symmetrical phasic movements of all four limbs were observed at all sleep stages other than REM sleep. Although movements other than these symmetrical body movements appeared to be normal in this case, the frequency of twitch movements showed an abnormal pattern in each sleep stage in the two older cases. These findings suggest that in the brainstems of younger cases with LNS the REM-non REM generator as well as multiple neurotransmitter systems influencing body movements during sleep remain relatively normal, but become progressively impaired in adult cases. Severe obstructive apnea was observed in one case with hypothyroidism, but there were no respiratory abnormalities in other two cases.

Spontaneous movements during sleep in children: temporal organization and changes with age

Developmental changes in the temporal organization of spontaneous movements during sleep was studied in children between 9 months and 11 years of age. Subjects were monitored in the home environment for the entire sleep period using actigraphy and videography. Rhythmicity in sleep-related spontaneous movements was examined using FFT and chi-square periodogram time series analyses. A dominant periodicity of 60-120 minutes was identified which was found to progressively lengthen with age. A microanalysis of the temporal structure of movements revealed a developmental decline in bout duration, but a paradoxical increase in bout frequency. These results show that motor activity becomes less robust and more fragmented as development progresses while retaining underlying rhythmic integrity, and argue for the dynamic influence of CNS maturation on the organization and expression of sleep-related spontaneous movements.