Rosemary S.C. Horne

Sudden infant death syndrome

Sudden infant death syndrome (SIDS) continues to be the most common cause of postneonatal infant death. SIDS is a complex, multifactorial disorder, the cause of which is still not fully understood. However, much is known now about environmental risk factors, some of which are modifiable. These include maternal and antenatal risk factors such as smoking during pregnancy, as well as infant-related risk factors such as non-supine sleeping position and soft bedding. Emerging evidence also substantiates an expanding number of genetic risk factors. Interactions between environmental and genetic risk factors may be of critical importance in determining an infants actual risk of SIDS. Although no practical way exists to identify which infants will die of SIDS, nor is there a safe and proven prevention strategy even if identification were feasible, reducing exposure to modifiable risk factors has helped to lower the incidence of SIDS. Current challenges include wider dissemination of guidelines to all people who care for infants, dissemination of guidelines in culturally appropriate ways, and surveillance of SIDS trends and other outcomes associated with implementation of these guidelines.

Accelerated Maturation and Abnormal Morphology in the Preterm Neonatal Kidney

Nephrogenesis is ongoing at the time of birth for the majority of preterm infants, but whether postnatal renal development follows a similar trajectory to normal in utero growth is unknown. Here, we examined tissue collected at autopsy from 28 kidneys from preterm neonates, whose postnatal survival ranged from 2 to 68 days, including 6 that had restricted intrauterine growth. In addition, we examined kidneys from 32 still-born gestational controls. We assessed the width of the nephrogenic zone, number of glomerular generations, cross-sectional area of the renal corpuscle, and glomerular maturity and morphology. Renal maturation accelerated after preterm birth, with an increased number of glomerular generations and a decreased width of the nephrogenic zone in the kidneys of preterm neonates. Of particular concern, compared with gestational controls, preterm kidneys had a greater percentage of morphologically abnormal glomeruli and a significantly larger cross-sectional area of the renal corpuscle, suggestive of renal hyperfiltration. These observations suggest that the preterm kidney may have fewer functional nephrons, thereby increasing vulnerability to impaired renal function in both the early postnatal period and later in life.

Cognitive and academic functions are impaired in children with all severities of sleep-disordered breathing

STUDY OBJECTIVE The impact of the broad spectrum of SDB severity on cognition in childhood has not been well studied. This study investigated cognitive function in children with varying severities of SDB and control children with no history of SDB. METHODS One hundred thirty-seven children (75 M) aged 7-12 were studied. Overnight polysomnography (PSG) classified children into four groups: primary snoring (PS) (n = 59), mild obstructive sleep apnea syndrome (OSAS) (n = 24), moderate/severe OSAS (n = 19), and controls (n = 35). Cognition was measured with a short battery of psychological tests including the Wechsler Abbreviated Scale of Intelligence (WASI), the Wide Range Achievement Test-3rd Edition (WRAT-3), the Rey Complex Figure Test (RCFT) and the Controlled Oral Word Association Test (COWAT). RESULTS There was lower general intellectual ability in all children with SDB regardless of severity. Higher rates of impairment were also noted on measures of executive and academic functioning in children with SDB. CONCLUSIONS Our findings suggest that neurocognitive deficits are common in children with SDB regardless of disease severity, highlighting that such difficulties may be present in children in the community who snore but are otherwise healthy; thus our results have important implications for the treatment of pediatric SDB.

Elevated Blood Pressure During Sleep and Wake in Children With Sleep-Disordered Breathing

OBJECTIVE: Sleep-disordered breathing (SDB) in adults has been associated with elevated blood pressure (BP); however, the effects of severity of SDB on BP in children are uncertain. We addressed this issue by measuring BP noninvasively and continuously during sleep in children with a range of severities of SDB and in a group of nonsnoring control children. METHODS: A total of 105 children referred for assessment of SDB and 36 nonsnoring controls were studied. Routine polysomnography (PSG) was performed with continuous BP monitoring. Children were assigned to groups according to obstructive apnea/hypopnea index (OAHI). BP data were categorized as quiet awake (recorded before sleep onset), non–rapid eye movement sleep 1 and 2 combined, slow-wave sleep, and rapid eye movement sleep. RESULTS: BP during awake before sleep onset and during overnight sleep was elevated by 10 to 15 mm Hg in the 3 SDB groups compared with the control group; this finding was independent of SDB severity. BP during stable sleep (with respiratory events and movements excluded) was also elevated in the children with OSA compared with the control group. BP was elevated in rapid eye movement sleep compared with the non–rapid eye movement sleep, and heart rate was higher during wake state than in all sleep states. CONCLUSIONS: We recorded BP continuously overnight and found that SDB, regardless of the severity, was associated with increased BP during sleep and wake compared with nonsnoring control children. These findings highlight the importance of considering the cardiovascular effects of SDB of any severity in children, and the need to review current clinical management that focuses primarily on more severe SDB.

Validation of actigraphy for determining sleep and wake in children with sleep disordered breathing.

There have been limited studies of the validation of actigraphy for the determination of sleep and wake in children and in this study we aimed to compare wrist actigraphy with polysomnography (PSG). We studied 45 children (29 M/16 F), aged between 1 and 12 years (5.8 ± 2.7 years, mean ± SD). Actigraphic data were collected during standard overnight PSG. Data from the actiwatch were analysed over four separate activity threshold settings (low, medium, high, auto). Actigraphic data were compared epoch‐by‐epoch with the matching PSG. Sleep time was not different from PSG values for the low or auto activity thresholds, but was significantly less on the medium and high activity thresholds (P < 0.05). In contrast, the low and auto activity thresholds significantly underestimated wake time (P < 0.05), whilst that recorded on the medium and high activity thresholds were not different to PSG values. Agreement rates across the thresholds were all high ranging from 85.1% to 88.6%. Predictive value for sleep and sensitivity were also high with values ranging from 91.6% to 94.9% and 90.1% to 97.7%, respectively. In contrast, predictive value for wake and specificity were low ranging between 46.7–65.6% and 39.4–68.9%, respectively. There was no effect of subject age, OAHI or PSG arousal index on AR for any of the activity thresholds. We conclude that actigraphy is a reliable method for determining sleep in children when compared against PSG. Actigraphy may be a useful tool in paediatric sleep clinics and research.

Swaddling and the Risk of Sudden Infant Death Syndrome: A Meta-analysis

CONTEXT: Swaddling is a traditional practice of wrapping infants to promote calming and sleep. Although the benefits and risks of swaddling in general have been studied, the practice in relation to sudden infant death syndrome remains unclear. OBJECTIVE: The goal of this study was to conduct an individual-level meta-analysis of sudden infant death syndrome risk for infants swaddled for sleep. DATA SOURCES: Additional data on sleeping position and age were provided by authors of included studies. STUDY SELECTION: Observational studies that measured swaddling for the last or reference sleep were included. DATA EXTRACTION: Of 283 articles screened, 4 studies met the inclusion criteria. RESULTS: There was significant heterogeneity among studies (I2 = 65.5%; P = .03), and a random effects model was therefore used for analysis. The overall age-adjusted pooled odds ratio (OR) for swaddling in all 4 studies was 1.58 (95% confidence interval [CI], 0.97–2.58). Removing the most recent study conducted in the United Kingdom reduced the heterogeneity (I2 = 28.2%; P = .25) and provided a pooled OR (using a fixed effects model) of 1.38 (95% CI, 1.05–1.80). Swaddling risk varied according to position placed for sleep; the risk was highest for prone sleeping (OR, 12.99 [95% CI, 4.14–40.77]), followed by side sleeping (OR, 3.16 [95% CI, 2.08–4.81]) and supine sleeping (OR, 1.93 [95% CI, 1.27–2.93]). Limited evidence suggested swaddling risk increased with infant age and was associated with a twofold risk for infants aged >6 months. LIMITATIONS: Heterogeneity among the few studies available, imprecise definitions of swaddling, and difficulties controlling for further known risks make interpretation difficult. CONCLUSIONS: Current advice to avoid front or side positions for sleep especially applies to infants who are swaddled. Consideration should be given to an age after which swaddling should be discouraged.

Actigraphy correctly predicts sleep behavior in infants who are younger than six months, when compared with polysomnography.

Actigraphy has been widely used in adults and children. In infants, validation of actigraphy has typically used a comparison with behaviorally determined sleep state classification rather than polysomnography (PSG). This study validated actigraphy against PSG for determining sleep and waking states in infants who were younger than 6 mo. Twenty-two healthy infants, 13 term and 9 preterm, were studied at three different matched postconceptional ages. Actigraph data were compared with PSG recordings in 1-min epochs. Agreement rate (AR), predictive value for sleep, predictive value for wake, sensitivity. and specificity were calculated and compared between activity thresholds and across ages with two-way ANOVA for repeated measures. Thirty-two validation studies were analyzed. Overall AR with PSG of 93.7 ± 1.3 and 91.6 ± 1.8 were obtained at 2–4 wk and 5–6 mo, respectively, at the low activity threshold setting, whereas the auto activity threshold gave the best agreement with PSG at 2–4 mo (AR 89.3 ± 1.3%). Sensitivity values of 96.2 ± 1.1% at 2–4 wk, 91.2 ± 1.5% at 2–4 mo, and 94.0 ± 1.9% were obtained at these same settings. There was no difference across ages in AR or sensitivity. PVW and specificity values were low in this study. We conclude that actigraphy is a valid method for monitoring sleep in infants who are younger than 6 mo.

Neurobehavioral function is impaired in children with all severities of sleep disordered breathing

OBJECTIVE Sleep disordered breathing (SDB) is common in children and ranges in severity from primary snoring (PS), to obstructive sleep apnea syndrome (OSAS). This study investigated everyday function (behavior, attention, executive skills) in children with varying degrees of SDB and control children with no history of SDB recruited from the community. METHODS One hundred thirty-six children aged 7-12 were studied. Routine overnight polysomnography (PSG) classified children into 4 groups: PS (n=59), mild OSAS (n=24), moderate/severe OSAS (n=18), and controls (n=35). Behavioral function and behavioral aspects of attention and executive function were assessed using the Child Behavior Checklist (CBCL) and the Behavior Rating Inventory of Executive Function (BRIEF). RESULTS Children with all severities of SDB had significantly higher rates of total, internalizing and externalizing behavioral problems compared to control children. Increased rates of behavioral executive dysfunction were also found across the SDB spectrum. CONCLUSION Our findings suggest that behavioral, attention, and executive function difficulties are present in children with PS as well as OSAS. These results have implications for the treatment of milder forms of SDB, particularly PS, which is commonly viewed as benign.

The use of actigraphy for assessment of the development of sleep/wake patterns in infants during the first 12 months of life

Maturation of sleep/wake patterns is one of the most important physiological developments during the first year of life. In this study, we aimed to compare the use of actigraphy and parental sleep diaries (SD) for recording the development of sleep/wake patterns longitudinally in term infants in their own home environments over the first 12 months of life. Twenty healthy term infants (7F/13M) were studied for 3 days each month in their own homes over the first 12 months of life. Sleep/wake patterns were recorded using both SD and actigraphy (AW) (AW64, Mini Mitter Co. Inc., Sunriver, OR, USA). The development of sleep and wake was analysed over 24 h, during the day (08:00–20:00 hours) and during the night (20:00–08:00 hours). A total of 186 studies had complete data sets for both analysis methods. Overall, there was no difference between methods of measurement for determination of the total percentage of sleep or wake over 24 h, or for the total percentage of sleep or wake during the day. However, at night, AW scored less time asleep (73.3 ± 0.9%) and more time awake (26.7 ± 0.9%) compared with the SD (80.7 ± 1.04% and 19 ± 1.0%, respectively, P < 0.001). Mean percentage sleep during the day decreased from 51% at 1 month to 28% at 12 months with the 1‐month values being significantly higher than all other ages, while mean percentage sleep at night was only different between 1 month and 11 and 12 months. In conclusion actigraphy provides a useful tool for assessing the development infant sleep.

Effects of maternal tobacco smoking, sleeping position, and sleep state on arousal in healthy term infants

Objectives: To investigate whether a history of maternal tobacco smoking affected the maturation of arousal responses and whether sleeping position and infant age alters these relations. Design: Healthy term infants (13 born to mothers who did not smoke and 11 to mothers who smoked during pregnancy) were studied using daytime polysomnography on three occasions: (a) two to three weeks after birth, (b) two to three months after birth, and (c) five to six months after birth. Multiple measurements of arousal threshold in response to air jet stimulation were made in both active sleep (AS) and quiet sleep (QS) when infants slept both prone and supine. Results: Maternal smoking significantly elevated arousal threshold in QS when infants slept supine at 2–3 months of age (p<0.05). Infants of smoking mothers also had fewer spontaneous arousals from QS at 2–3 months in both prone (p<0.05) and supine (p<0.001) sleeping positions. In infants of non-smoking mothers, arousal thresholds were elevated in the prone position in AS at 2–3 months (p<0.01) and QS at 2–3 weeks (p<0.05) and 2–3 months (p<0.001). Conclusions: Maternal tobacco smoking significantly impairs both stimulus induced and spontaneous arousal from QS when infants sleep in the supine position, at the age when the incidence of sudden infant death syndrome is highest.