World Journal Of Pediatrics-articles

Author Affiliations: Carl-Thiem-Klinikum Cottbus gGmbH, Clinic for Paediatric and Adolescent Medicine, Academic Teaching Hospital of the Charité – Universitätsmedizin Berlin, Cottbus, Germany (Meyer LE, Erler T)

Corresponding Author: Lars E Meyer, Carl-Thiem-Klinikum Cottbus, Klinik für Kinder- und Jugendmedizin, Thiemstr. 111, 03048 Cottbus, Germany (Tel: +49 355 46 2336; Fax: +49 355 46 2077; Email: l.meyer@ctk.de)

Background: This study was undertaken to compare the sleep profiles of healthy infants in swaddling and sleeping bag conditions.

Methods: Polysomnographs of 85 healthy infants (40 in the study group, 45 in the control group) with a mean age of 7.5 weeks were recorded in the sleeping laboratory. A positive decision from the local Ethics Committee and the written consent of the parents were obtained for the study.

Results: Swaddling significantly reduces the rate of spontaneous waking (events/h: 1.39 [0.85-2.77] vs. 2.81 [1.49-4.53], P=0.020) and the number of sleep stage changes (events/h: 3.82 [2.97-5.16] vs. 5.37 [3.58-6.67], P=0.015). Swaddling promotes quiet sleep (36.37% [29%-40.31%] vs. 30.2% [24.45%-36.78%], P=0.032), the time spent awake was decreased (8.98% [4.62%-14.25%] vs. 14.17% [9.2%-18.94%], P=0.001) and sleep efficiency was increased (91.02% [85.75%-95.38%] vs. 85.83% [81.06%-90.8%], P=0.001).

Key words: infantile regulatory disorder; polysomnography; sudden infant death syndrome; swaddling

infantile regulatory disorders are common in our society. Clinical experience shows that almost every 4th to 5th child in pediatric treatment suffers from a disorder of this kind.^[1] Sleep disorders occur most frequently, followed by feeding disorders and excessive crying.^[2] Infants affected by a regulatory disorder, who often wake in the night, sometimes cry excessively, stay awake longer, and need considerably more help in going to sleep, are a great cause of stress for parents.^[3]These children are at increased risk of abuse. The parents who themselves suffer from a lack of sleep are prone to emotional outbursts: there is a risk for shaken baby syndrome, an injury with a high mortality rate, whereby almost all survivors suffer from severe neurological and/or cognitive damage.^[1,4] A further risk to such children is in the encouragement of an unhealthy sleep pattern. Excessive crying and infantile sleep disorders are the main reasons stated by parents for laying their children in prone sleeping position rather than in supine position.^[5,6] Children seem more content when placed prone and are believed to sleep more quietly, so that the parents are not required to intervene so often during the night. However, despite prevention campaigns prone sleeping is a fundamental risk factor for sudden infant death syndrome (SIDS) and continues to be the most frequent post-neonatal cause of death in many industrialised countries such as the USA or Germany.^[7,8] Studies have shown that through measures aimed at increasing parents' awareness with regard to their babies' sleeping position the frequency of the prone position and consequently the incidence of SIDS could be decreased by approximately 50%.^[9,10]

It therefore seems reasonable to evaluate methods which promote quiet infant sleep in the supine position and therefore relieve overburdened parents. Improved sleep could reduce the risk of child abuse and help to lower the rate of SIDS. Multimodal treatment concepts now exist for infantile regulatory disorder. One strategy for promoting quiet sleep is known as swaddling.^[11,12]Some children benefit if their limbs are drawn towards the center of their body for sleeping. They experience a balance, a physical containment, which at the same time makes them feel more secure.

Swaddling is a traditional custom in which infants are wrapped tightly but comfortably in sheets, blankets or similar objects.^[13] The limbs are fixed more or less tightly to their body such that the children no longer have complete freedom of movement. Prior to the 18th century, swaddling was a universal care method. However, the custom became increasingly forgotten in Europe in the period leading up to the Industrial Revolution. The rejection of swaddling was a reflection of the liberal views then became more widespread in Western European society. Moreover, it was considered unnatural and its practice became confined to the rural population of Eastern Europe. Nevertheless, swaddling is still practised in some cultures in the Middle East and South America and is now enjoying increased popularity in industrialized countries such as the United States, the UK and the Netherlands. The main reason for the revival of swaddling is that babies sleep more quietly. Experimental studies now support this observation that infants subject to swaddling while sleeping tend to wake less frequently, appear to sleep longer and are more likely to return to sleep on their own.^[12,14,15]

Increased public interest is demonstrated by an increasing number of publications on the topic of swaddling.^[16] Comparisons with the traditional baby sleeping bag are being discussed and the advantages and disadvantages of the method are being weighed up. For example, swaddling promotes neuromuscular development in premature babies, supports self-regulatory mechanisms, and can prevent physical unrest.^[17,18] Phases of crying are significantly reduced and, during painful procedures, a comforting effect is observed.^[19,20] Swaddling can also assist newborns with cerebral defects and/or withdrawal symptoms.^[21,22]

Swaddling seems to be a promising method of care which promotes quiet sleep in infants. Due to this, our study center has been using a swaddling sleeping bag ("Cosyme", Cosyme GmbH, Germany) for putting newborns and infants to bed for approximately two years as an alternative to the traditional sleeping bag which allows their arms to move freely. This uses flexible straps to fix the arms of the infants to their body, thus creating swaddling conditions (Fig.). The caregivers have since been unanimous in reporting an apparently more peaceful and quieter sleep pattern. Although the number of studies on this topic is increasing, the mechanisms and the effects on infant sleep are largely unclear. The aim of the present study was a polysomnographic comparison of the sleep patterns in infants under swaddling and sleeping bag conditions by way of a prospective controlled randomised study.

Polysomnographs were recorded for 85 infants (50 females, 35 males) with a mean age of 52 (±21) days. The infants were recruited prospectively, taking inclusion and exclusion criteria into consideration, from a larger group of infants as part of an SIDS prevention campaign. Preliminary results of the study had already been published previously.^[23]

The infants were required to be clinically healthy at the time of the study and between one and four months of age. The family history did not include any SIDS incident. Excluded were former premature babies and children with a birth weight of less than 2500 g. In line with the current study no other sociological or demographical data were being investigated. The study did not cause any added burden to the subjects and there was no remuneration. A positive decision from the local ethics committee and written consent from the parents or legal guardians were obtained for the study.

The polysomnographs were recorded in the Carl-Thiem Clinic sleep laboratory in Cottbus (Dept. of Pediatric and Adolescence Medicine) in accordance with the standardized guidelines of the German Sleep Society (DGSM) for performing polysomnography in infants and older children.[24] These guidelines regulate the conditions of sleeping circumstances, the technical gadgets and which parameters need to be recorded. The patients who were examined in the sleeping laboratory were from cities and the rural areas.

The infants were examined lying in a supine sleeping position and randomized, either in a traditional sleeping bag allowing their arms to move freely (45 subjects in the control group) or a swaddling sleeping bag ("Cosyme", Cosyme GmbH, Germany) with their arms strapped to their body (40 subjects in the "Cosyme" study group). During this study each infant did not use anything other than these sleeping bags. The examination of the infants was prepared in a habitual manner such as feeding, cradling, singing nursery songs. After the measuring sensors were stuck on, the light of the sleeping laboratory was turned off. Either mother or nurse stayed behind until the child fell asleep. If the child happened to wake up during examination, adequate procedures were taken to put the child back to sleep. All polysomonographs were performed under identical conditions and ended only after the child had woken independently. Sixty-four infants were recorded at night (36 infants from the control group, 28 from the study group) and 21 infants were recorded during their afternoon sleep (9 from the control group, 12 from the study group). Numerous variables were recorded continuously and simultaneously: electroencephalogram, electromyogram, electroculogram, electrocardiogram, thoracic impedance, and oronasal airflow using a thermistor. Oxygen saturation was measured over 5 second periods and the mean value was determined. The polysomnographs were recorded digitally using the Alice 3TM system, version 1.20 (Healthdyne, Inc., USA, marketed in Germany by Heinen & Löwenstein) and subsequently validated manually. Sleep was broken down into stages in accordance with the definition by Anders, Emde and Parmelee (Table 1).^[25] Table 2 provides an overview of the determined sleep profiles and measured cardio-respiratory parameters.

The data were evaluated using the SPSS 12.0 statistics software for Windows (SPSS Inc., USA). The non-parametric Mann-Whitney U test was used for the statistical analysis of the parameters measured, with the critical significance level set to P<0.05. Values were given as median and inter-quartile range values.

Detailed results are provided in Table 3. In summary, there was no difference in the registration time for all 85 infants. There were only slight differences in the majority of the cardio-respiratory parameters under swaddling and sleeping bag conditions. In particular, there were no important differences in the rate and maximum duration of cases of central or obstructive apnoea. A statistical significance was achieved in the oxygen saturation comparisons, i.e., lower saturation values were found under swaddling conditions than in the control group on the basis of the distribution. However, in both groups, the values were all within the normal range and there was no particular relevance to this finding.

The differences in sleep characteristics are obvious. As shown in Table 3, the swaddling sleep in the supine position compared with sleep in the sleeping bag was accompanied by a significantly higher sleep efficiency (91.02% vs. 85.83%; P=0.001). The children experienced fewer sleep stage changes (events n/h: 3.82 vs. 5.37; P=0.015) and the rate of spontaneous waking was decreased (events n/h: 1.39 vs. 2.81; P=0.02). The total waking time was reduced (8.98% vs. 14.17%; P=0.001) in favor of the quiet sleep duration (36.37% vs. 30.2%; P=0.032). No active sleep displacements were observed.

The results of the study confirm the subjective observations that fixing the limbs by means of swaddling leads to quieter sleep than in sleeping bag conditions in which the arms can move freely. The children sleep more deeply and wake less spontaneously. As a result, parental intervention is required less frequently. The children appear to be quieter and more peaceful while sleeping.

The findings are supported by further international publications.^[12,23,26] A common explanation for the swaddling phenomenon focuses chiefly on the limited limb movement.^[12,14,16] The motor restriction may lead to a decrease in the rate of spontaneous waking via a reduction in the proprioceptive stimuli of the reticular activation system. Moreover, a decrease in the motor activity means that infants can fall asleep again more quickly if they do wake up.^[12]

With regard to the cardio-respiratory sleep parameters, there are no relevant differences between the study group and the control group. Although a statistically significant difference in the oxygen saturation was calculated over the entire sleep period, the values for both groups were always within the reference range.

In contrast to these results, published papers and some of our preliminary studies describe changes in the respiratory rate and heart rate, especially during quiet sleep.^[11,13,23] The effect of swaddling tightness is under discussion: thoracic compression is intensified with swaddling.^[27] As a result, the depth of breathing is restricted. This leads to a reduction in ventilation and oxygen concentration in the blood. As a form of compensation, this causes increased respiratory activity and involuntarily stimulates the cardiac activity. However, the differences in active and quiet sleep were not adequately explained using this model. The physiological effects of swaddling on the newborn or infant are still not fully understood. It therefore seems appropriate to rule out swaddling for cardio-respiratory compromised children on the basis of the data currently available. There is a lack of data on the medium to long-term effects and there are indications of an increased risk of acute respiratory infections.^[16,28] Thermistors which are used to measure the oronasal flow tend to cause artefacts such as pseudo-apnea or pseudo-obstruction. This must be carefully taken into consideration when evaluating the respiratory data.

The restricted freedom of limb movement and the quieter sleep associated with this are to be regarded as reasons for the fact that the risk of SIDS in infants may be minimized in the supine position under swaddling conditions. The infants are less likely to turn themselves onto their stomachs and they become less frequently entangled in loose sheets, pillows etc., which are factors resulting in an increased risk of suffocation.^[29] It should be pointed out that the risk of SIDS is increased with a combination of swaddling and the prone position. One study has shown that the prone position alone increases the risk of SIDS by approximately a factor of three and the combination of prone position and swaddling can increase the risk up to twelve folds.^[30] One reason for this under discussion is the reduced waking capacity under swaddling conditions.^[31,32] Overall, however, swaddling does appear to have a positive effect on the safety of the infant's sleep. This interpretation is supported by prevailing epidemiological data which demonstrate a decreased SIDS risk in the supine position with swaddling compared with the supine position without swaddling.^{[29,30,33,34]} In the light of this information, it seems appropriate only to use swaddling conditions up to an age at which infants can turn themselves independently from the supine position to the prone position. No precise age, however, can be stated.

Further potential effects and disadvantages of swaddling discussed in published literatures, such as the influence on excessively crying infants, the increased risk of promoting dislocation of the hip, the risk of hyperthermia or a vitamin D deficiency, were not taken into account as part of this study. A detailed, up-to-date overview is provided in the publication of van Sleuwen et al in 2007.^[16]

This study leads to the following conclusions: swaddling promotes sleep efficiency in healthy infants sleeping in a supine position: The infants wake less frequently and have shorter waking phases, they sleep more deeply and experience fewer sleep stage changes. The infants appear to sleep more quietly and peacefully. The use of a swaddling sleeping bag for infants with difficulties in falling asleep or sleeping through the night as a result of infantile regulatory disorder is a possible alternative to the traditional sleeping bag. The parents are no longer required to intervene as often during the night. For this reason, it could be a promising approach to lowering the child abuse and SIDS rate for such children. Any potential complications should be fully clarified before routine childcare use, and therapeutic use with children that are restless due to pain, infection, etc needs to be verified.

Preliminary results of this study have been previously published in the trade journal Somnologie 2009;13:24-28 (Springer Verlag, Germany).

Ethical approval: A positive decision from the local Ethics Committee as well as written consent from the parents or legal guardians were obtained for the study.

Contributors: Meyer LE wrote the main body of the article under the supervision of Erler T.

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