Over the past few decades, there has been an increased focus and growing number of studies that implicate the importance of sleep on newborn and infant health. Sleep is an essential part of life and is a necessary function of proper development. As the literature expands, we have increased our understanding of sleep, particularly as it pertains to growth, neurological development, and emotional well-being.
Sleep deprivation or disturbances in sleep during early development can lead to poor overall health, decreased emotional regulation, poor decision-making, inattention, increased adiposity, and decreases in academic performance.1 These findings were first noted in adults, but recent studies also suggest that signs of these deficiencies can be seen as early as the neonatal period.2 Attention to these details is important, as early sleep intervention can have lasting positive effects on development.
Sleep has been defined as a reversible state of minimal interaction and decreased responsiveness with the environment.3 Although it is a physical decrease in responsiveness, it can be argued that it is a time of enhanced neurological function and physiologic activity. Sleep is composed of four primary stages including the awake state, transitional sleep, active sleep, and quiet sleep. Each category carries a different level of wakefulness and is defined by a progression of changes regarding physical characteristics (Table 1).
Sleep State Characteristics
In the awake state, eyes are open with regular or slowing eye movements, the body continues to have normal movements with an increase in startling, there continues to be irregular respirations, an electroencephalogram (EEG) will demonstrate a continuous medium voltage pattern, and an amplitude integrated EEG (aEEG) will show a narrow bandwidth. In the transitional state, eye movements begin to slow with lengthened periods of eye closing, both motor and facial activity will start to decrease (although vocalization begins to increase), respirations become more regular, and the EEG will show a continuous high voltage pattern while an aEEG will show a variable bandwidth. As sleep progresses to the active state, eyes will be closed with rapid eye movement (REM). Motor and facial activity will be limited with occasional slow twitches and bursts of vocalization, and respirations will be irregular. The EEG in this state will show continuous low voltage and the aEEG will have a narrow bandwidth. Lastly, in the quiet sleep phase, eyes will be closed with relatively no eye or body movements. Facial expressions will be limited, and the infant will have occasional sighs. The EEG in this state will be slow, but have a wide range of voltage, and the aEEG will show a wide bandwidth.4
It is important to recognize that as an infant develops, these sleep states continuously change. For instance, the number of sleep cycles during the daytime will decrease as an infant gets older.4 Other alterations in sleep that can vary with age include lengthening of the interval between sleep, decreased REM activity, decreased active sleep, increased quiet sleep, and shortening of the time spent in the transitional sleep stage.5 The sections to follow will outline the changes in sleep based on key milestones in development.
Fetal Sleep Patterns
Although simple movement in the fetus can be detected as early as 7 to 8 weeks postmenstrual age, conscious movement and distinct patterns of motion are not noted until 15 weeks gestation. Even later are sleep states, as these are not present until the second half of gestation. During this latter half of pregnancy, it is speculated that the cyclical rhythm of fetal wake and sleep patterns are guided by the placental transfer of maternal melatonin.6
Regarding the amount of time spent sleeping, in fetal lamb studies, subjects were noted to be in both active and quiet sleep for the majority of gestation with only occasional periods of wakefulness. This observation is largely due to environmental factors in-utero that promote sleep, including both warmth and various chemicals (prostaglandin E2, pregnanolone, adenosine, and allopregnanolone). Breathing and body movements once thought to be a component of the awake state, occur during sleep states and are important in strengthening the respiratory muscles responsible for extrauterine life.
Episodes of true wakefulness are rarely observed in-utero, but when they occur, they are defined as periods of vigorous activity with increases in heart rate and swallowing. As the fetus approaches 28 weeks of gestation, awake states will occur more frequently, and distinct activity patterns can be noted more clearly.7
Preterm and Term Sleep Patterns
Similar to the fetus, a premature neonate can have clear periods of active and quiet sleep that can be detected as early as 25 to 27 weeks of gestation. Postnatally, these infants can spend upward of 90% of their time sleeping, compared to their full-term counterparts who sleep only about 70% of the time.7 The key difference with age is the amount of time spent in active sleep with REM activity. A premature infant will spend about 80% of their time in active sleep, whereas a full-term infant will spend most of the time in the quiet sleep phase. Although the term baby spends less time in the active sleep phase, they experience significantly more REM activity when compared to the preterm infant. This indicates better organization of the active sleep phase and a noted overall maturity of sleep-wake activity patterns that occurs with age.8 Low or fragmented REM activity is often found in neonates with developmental delays. Infants with higher medical risk scores often have less REM activity during their active sleep phases. These same infants have increased fussiness and longer periods of crying.9
Once a premature infant is corrected to term gestational age, they can appreciate sleep-wake cycles similar to full-term neonates. Extremely premature neonates have in fact been noted to mature their sleep-wake cycles sooner than their term counterparts. Throughout the first few months of life, premature neonates will have longer sleep durations during the day and night as well as have an increase in number of nighttime awakenings when compared to term babies. At age 6 months, infants born prematurely have been noted to be noisy breathers while sleeping and will also have an increase in number of apneas or hypopneas. Some studies suggest upward of 80% of premature neonates will experience one or more apneic or hypopneic events per hour.10 This number, however, decreases with age and seldom requires intervention.
Sleep in the Hospital Setting
Infants in the neonatal intensive care unit (NICU) are subject to several issues contributing to poor sleep. This is compounded by the fact that premature infants and those with certain diseases are at an increased risk for abnormal neurological development (Table 2). Over the past decade there has been an increase in literature suggesting that sleep disruption caused by even routine handling of neonates can lead to poor brain maturation.11
Sleep Disruption in Common Neonatal Conditions
In the NICU, several components of care can contribute to sleep disturbances. These include frequent interventions (laboratory testing or procedures), pharmacologic treatment (sedation or antiepileptic medications), loud or disruptive ambient noise, abnormal day-night cycles, and bright lighting.
One study11 observed neonates for a 4-hour block of sleep that found that only 50% of these patients were able to complete a full sleep-wake cycle before being disturbed for care. During provider contact, 57% of these patients had some level of awakening. Often these awakenings were associated with desaturations or apneic events and potential further arousal with any needed intervention.11 Although there have not been any studies that associate sleep disturbances with the need for respiratory support, it is important to recognize the potential for negative impact on sleep.
Tools for Measuring Sleep
There are many tools for the measurement of sleep that range from observational, which is least invasive, to more technology-dependent invasive methods. The clinical assessments that are least invasive include assessment of heart rate and behavioral classification of sleep. Each are well studied, reliable, and do not need any technological support. Furthermore, they do not cause any long-term damage and can be used as an assessment method for a significant length of time.
Heart rate assessment or monitoring of heart rate variability has been studied as a marker for neonatal sleep. This method is more commonly used in both adults and pediatrics to assess disease-state progression. In this case, an assessment of beat-to-beat variability is conducted. Any dynamic changes in slowing or increase in heart rate reflects the autonomic nervous system. The interaction between neural inputs of the parasympathetic and sympathetic systems guide these changes and variabilities in heart rate. After about 30 weeks corrected gestational age, these heart rate variability monitors can interpret slowing as it relates to sleep and quickening as is associated with periods of wakefulness.12
Although neonatal sleep is best assessed through technology, interpretation of a neonate's physical examination findings and behavioral patterns can help to determine which sleep state they are in. As described in Table 1, each sleep state has several distinguishable motor movements. Most commonly eye movements (opening and closing), vocalization (no vocalization to mild sighing), and motor coordination (from normal movements to startles or small jerks) can be used, as each characteristic has a pattern corresponding to a distinct sleep state. It is important to be mindful of respirations as well, as respiratory rate and quality can also be useful in classifying sleep.12
Although the gold standard in measuring sleep lies with technology and more invasive monitoring, clinical observation can be especially useful in settings where this technology is not available. In these situations, behavioral classification in conjunction with heart rate variability may be able to give observers the best estimate of a neonate's sleep status.
The more invasive methods of sleep measurement include aEEG, EEG, and polysomnography. Each of these modalities requires a technological interface and use of probes and monitors to achieve a more comprehensive assessment of an infant's sleep.
The least invasive is an aEEG. With this modality, two leads are placed bi-parietally on the neonate's head (each probe corresponding to the parietal lobe on that side of the head). The clinician in this instance can detect the presence of the sleep-wake cycle at the bedside. A wide bandwidth corresponds with quiet sleep, whereas a thin or narrow bandwidth will be associated with wakefulness or active sleep. Cyclic variation of the aEGG can first be seen in neonates at 26 weeks gestation, and the more traditional sleep-wake cycle will be seen at about 31 to 32 weeks of gestation.13
More invasive than aEEG is the traditional EEG, described in the neurology literature. In addition to a more in-depth description of brain function, this modality allows clinicians to observe brain and central nervous system maturation over time. Although its reliability begins only after a neonate reaches 30 weeks corrected gestation, it is a much more comprehensive look at the sleep-wake cycle. However, it is more sensitive to the dulling effects of pharmacotherapy.14
Finally, polysomnography is the most complete picture and the current gold standard when measuring sleep. In addition to EEG, this modality includes pulse oximetry, electrooculography, electrocardiography, and chin electromyography. With this technology, the clinician can measure sleep states, timing of apnea events, as well as the nature of the events (central versus obstructive), ultimately giving a global assessment of an infant's sleep.15
Healthy and normal sleep in newborns depends largely on a consistent routine. Proper management of daytime and nighttime routines is essential in optimizing an infant's developmental and physiologic sleep requirements. As this varies from child to child, it is important to remain adaptable while also recognizing issues with sleep and intervening in a timely manner. Evidence-based interventions that can be implemented in every setting include light modification, sound modification, infant massage, and skin-to-skin contact.
Light modification is a simple and relatively effortless change that can be made in every setting, particularly in the NICU. The benefit can be achieved through maintaining darkness or creating a day and night type pattern with the lighting. Studies demonstrated an association with shorter time to full feeds, decreased length of stay, and possible fewer ventilator days.16 An additional benefit is that with day-night cycled light pattern, infants develop a routine and tend to sleep longer in the night periods versus infants who did not have a cycled light pattern.17
Sound modification can have tremendous benefits. Infants who are exposed to excessive stimulation have been known to suffer from apnea, increased heart rate, and hearing deficits, thereby casuing possible speech and language difficulties in later development.18 A positive modification in addition to chaotic noise reduction would be that of music therapy. Neonates exposed to music have shown improvements in sleep, feeding, and heart rate stability.19 This effect is most prominently seen in preterm infants; however, all neonates can benefit from sound reduction and the bonding that comes from music.
Infant massage is an area of growing interest. Although there does not seem to be any direct benefit with regard to neurodevelopmental outcomes, the value of massage comes with its relative ease of learning, infant-parental bonding, and the alterations in sleep patterns. Infants demonstrate a decrease in sleep latency, remain asleep longer, and have fewer nighttime awakenings. Other benefits include decreased crying, lower pain scores, and increase in heart rate stability. Some studies have suggested an added importance in the preterm population with improvement in weight gain and a decrease in length of NICU stay.20
Lastly, is the well-studied and now widely adapted use of skin-to-skin contact (SSC). From as little as 1 hour per day over a 2-week period, benefits seen with this intervention are both physiologic and physical in nature. Neonates undergoing SSC had an increase in vital sign stability with fewer episodes of bradycardia, higher oxygen saturations, decreased hypothermia, and decreased respiratory rates. These infants also experienced improved overall growth with associated increases in the rates of exclusive breast-feeding and decreased episodes of hypoglycemia. Infant-parental bonding is also improved, as studies have demonstrated decreases in both infant and parental cortisol levels during times of SSC. Regarding sleep, neonates who benefited from SSC had fewer awakenings from sleep as well as better sleep organization.21
Infant sleep is often discussed during routine pediatric visits. These conversations consist of issues with sleep latency, short duration of sleep, and frequent nighttime awakenings.22 The recognition of these sleep deficiencies and providing early intervention can be crucial in preservation of a positive developmental outcome. Although the body of literature continues to grow, there seems to be a positive correlation between good sleep behavior and neurodevelopmental health.
The effects of poor sleep are manifold and can last throughout childhood. The deleterious effects can be observed across many systems, the most prominent being metabolic. Although the exact causality has not been identified, infants with abnormal sleep and shorter nighttime sleep duration were more likely to be overweight. These same infants also had the propensity to be overweight into childhood. This effect is also compounded further by poor diet and exercise habits.23
Regarding mental health, studies on sleep highlight the social-emotional issues with sleep disruption. Infants and children with later bedtimes and reduced nighttime sleep often showed more issues with separation distress, inhibition, anxiety, and depression. These social-emotional problems were magnified 5 times with just a small reduction in sleep time, 11 hours per day versus the average 13 to 14 hours.24 When studied at age 1 year, infants with lower sleep quality were predicted to have behavioral issues and attention-regulation problems at age 3 to 4 years, reiterating the importance of optimal sleep at an early age.25
Sleep is perhaps one of the most essential, but commonly overlooked elements of newborn growth and development. Although there has been a recent increase in the number of studies published on newborn and infant sleep, much is still left to be explored with further research. Evidence suggests that it is necessary to consider the implications of poor sleep on long-term outcomes, and furthermore understand how we can use markers of sleep disturbance to implement earlier interventions.
As a practitioner working with newborn and pediatric patients, a few other variables to recognize are parental education level, health literacy, socioeconomic status, and cultural differences that may influence sleep practice. Furthermore, the emphasis on maternal health with depression screening, stressing the risks of co-sleeping, and providing resources to temper parental burnout are also crucial in creating a positive sleep environment.26 Being mindful of interventions and therapies in this way are not only beneficial in establishing a thoughtful parent-practitioner relationship, but ultimately contribute positively to the care of each child.
- Chaput JP, Gray CE, Poitras VJ, et al. Systematic review of the relationships between sleep duration and health indicators in school-aged children and youth. Appl Physiol Nutr Metab. 2016;41(6)(suppl 3):S266–S282. doi:10.1139/apnm-2015-0627 [CrossRef] PMID:27306433
- Mirmiran M. The importance of fetal/neonatal REM sleep. Eur J Obstet Gynecol Reprod Biol. 1986;21(5–6):283–291. doi:10.1016/0028-2243(86)90006-7 [CrossRef] PMID:3721040
- Chervin RD, Dillon JE, Bassetti C, Ganoczy DA, Pituch KJ. Symptoms of sleep disorders, inattention, and hyperactivity in children. Sleep. 1997;20(12):1185–1192. doi:10.1093/sleep/20.12.1185 [CrossRef] PMID:9493930
- Fagioli I, Salzarulo P. [Temporal organization of sleep cycles in infants over 24-hour periods]. Rev Electroencephalogr Neurophysiol Clin. 1982;12(4):344–348. doi:10.1016/S0370-4475(82)80024-5 [CrossRef] PMID:7170380
- Barbeau DY, Weiss MD. Sleep disturbances in Newborns. Children (Basel). 2017;4(10):E90. doi:10.3390/children4100090 [CrossRef] PMID:29053622
- Rurak D. Fetal sleep and spontaneous behavior in utero: animal and clinical studies. In: Walker D, ed. Prenatal and Postnatal Determinants of Development (Neuromethods). New York, NY: Humana Press; 2016:89–146.
- Anders TF, Keener MA, Kraemer H. Sleep-wake state organization, neonatal assessment and development in premature infants during the first year of life. Sleep. 1985;8(3):193–206. doi:10.1093/sleep/8.3.193 [CrossRef] PMID:4048735
- Holditch-Davis D, Scher M, Schwartz T, Hudson-Barr D. Sleeping and waking state development in preterm infants. Early Hum Dev. 2004;80(1):43–64. doi:10.1016/j.earlhumdev.2004.05.006 [CrossRef] PMID:15363838
- Arditi-Babchuk H, Feldman R, Eidelman AI. Rapid eye movement (REM) in premature neonates and developmental outcome at 6 months. Infant Behav Dev. 2009;32(1):27–32. doi:10.1016/j.infbeh.2008.09.00 [CrossRef] PMID:18996599
- Huang YS, Paiva T, Hsu JF, Kuo MC, Guilleminault C. Sleep and breathing in premature infants at 6 months post-natal age. BMC Pediatr. 2014;14(1):303. doi:10.1186/s12887-014-0303-6 [CrossRef] PMID:25510740
- Levy J, Hassan F, Plegue MA, et al. Impact of hands-on care on infant sleep in the neonatal intensive care unit. Pediatr Pulmonol. 2017;52(1):84–90. doi:10.1002/ppul.23513 [CrossRef] PMID:27362468
- Werth J, Long X, Zwartkruis-Pelgrim E, et al. Unobtrusive assessment of neonatal sleep state based on heart rate variability retrieved from electrocardiography used for regular patient monitoring. Early Hum Dev. 2017;113:104–113. doi:10.1016/j.earlhumdev.2017.07.004 [CrossRef] PMID:28733087
- Viniker DA, Maynard DE, Scott DF. Cerebral function monitor studies in neonates. Clin Electroencephalogr. 1984;15(4):185–192. doi:10.1177/155005948401500401 [CrossRef] PMID:6518653
- Dereymaeker A, Pillay K, Vervisch J, et al. Review of sleep-EEG in preterm and term neonates. Early Hum Dev. 2017;113:87–103. doi:10.1016/j.earlhumdev.2017.07.003 [CrossRef] PMID:28711233
- Joosten K, de Goederen R, Pijpers A, Allegaert K. Sleep related breathing disorders and indications for polysomnography in preterm infants. Early Hum Dev. 2017;113:114–119. doi:10.1016/j.earlhumdev.2017.07.005 [CrossRef] PMID:28711234
- Morag I, Ohlsson A. Cycled light in the intensive care unit for preterm and low birth weight infants. Cochrane Database Syst Rev. 2016;(8):CD006982. doi:10.1002/14651858.CD006982.pub4 [CrossRef] PMID:27508358
- Guyer C, Huber R, Fontijn J, et al. Very preterm infants show earlier emergence of 24-hour sleep-wake rhythms compared to term infants. Early Hum Dev. 2015;91(1):37–42. doi:10.1016/j.earlhumdev.2014.11.002 [CrossRef] PMID:25460255
- Brown G. NICU noise and the preterm infant. Neonatal Netw. 2009;28(3):165–173. doi:10.1891/0730-0822.214.171.124 [CrossRef] PMID:19451078
- Standley J. Music therapy research in the NICU: an updated meta-analysis. Neonatal Netw. 2012;31(5):311–316. doi:10.1891/0730-08126.96.36.1991 [CrossRef] PMID:22908052
- Juneau AL, Aita M, Héon M. Review and critical analysis of massage studies for term and preterm infants. Neonatal Netw. 2015;34(3):165–177. PMID:26802392
- Feldman-Winter L, Goldsmith JPCommittee on Fetus And NewbornTask Force On Sudden Infant Death Syndrome. Safe sleep and skin-to-skin care in the neonatal period for healthy term newborns. Pediatrics. 2016;138(3):e20161889. doi:10.1542/peds.2016-1889 [CrossRef] PMID:27550975
- Mindell JA, Lee C. Sleep, mood, and development in infants. Infant Behav Dev. 2015;41:102–107. doi:10.1016/j.infbeh.2015.08.004 [CrossRef] PMID:26386882
- Alamian A, Wang L, Hall AM, Pitts M, Ikekwere J. Infant sleep problems and childhood overweight: effects of three definitions of sleep problems. Prev Med Rep. 2016;4:463–468. doi:10.1016/j.pmedr.2016.08.017 [CrossRef] PMID:27617193
- Hysing M, Sivertsen B, Garthus-Niegel S, Eberhard-Gran M. Pediatric sleep problems and social-emotional problems. A population-based study. Infant Behav Dev. 2016;42:111–118. doi:10.1016/j.infbeh.2015.12.005 [CrossRef] PMID:26774862
- Sadeh A, De Marcas G, Guri Y, Berger A, Tikotzky L, Bar-Haim Y. Infant sleep predicts attention regulation and behavior problems at 3–4 years of age. Dev Neuropsychol. 2015;40(3):122–137. doi:10.1080/87565641.2014.973498 [CrossRef] PMID:26151611
- Field T. Infant sleep problems and interventions: a review. Infant Behav Dev. 2017;47:40–53. PMID:28334578
Sleep State Characteristics
||Eyes: open with rapid or slow eye movements
Motor: rapid startles with normal movements
Facial movements: frowning, smiling, crying, grimacing (with vocalization)
EEG: continuous, medium voltage (70–100 mcV)
aEEG: narrow bandwidth
||Eyes: periods of opening and closing, slow eye movement
Motor: slow startles with minimal movements
Facial activity: grimacing, intermittent sucking (with increased vocalization)
EEG: continuous, high voltage (100–200 mcV)
aEEG: variable bandwidth
||Eyes: closed with rapid eye movements
Motor: low tone with small, slow twitches
Facial movements: frowning, smiling (with bursts of sucking and vocalization)
EEG: continuous, low voltage (30–70 mcV)
aEEG: narrow bandwidth
||Eyes: closed with no eye movements
Motor: minimal to no movement
Facial movements: rhythmic mouth movement (with occasional sighs)
Respirations: slow and regular
EEG: slow, medium to high voltage (30–200 mcV)
aEEG: wide bandwidth
Sleep Disruption in Common Neonatal Conditions
|Chronic lung disease
||Definition: prolonged ventilator or oxygen support leading to significant respiratory disease
Sleep alteration: increased respiratory events (desaturations and apnea), hypoxia, and respiratory-related arousals during sleep
|Congenital heart disease
||Definition: anatomical cardiac deficits that lead to poor oxygenation and hypoxemia
Sleep alteration: delayed sleep-wake cycle for corrected gestational age
||Definition: disruption of cerebral blood flow leading to potentially poor neurodevelopmental outcome
Sleep alteration: delayed sleep-wake cycle (progressively worse with more severe injury)
|Inborn errors of metabolism
||Definition: disorders caused by enzyme deficiencies essential to metabolic pathways
Sleep alteration: spectrum of findings from no sleep-wake cycle to normal cycling, depending on the enzyme deficiency
|Neonatal abstinence syndrome
||Definition: abrupt discontinuation of maternal drug use to the chronically exposed fetus during pregnancy
Sleep alteration: opiate exposure leads to more active, but fragmented sleep, and the infant is easily arousable; selective serotonin reuptake inhibitor exposure leads to more active sleep and increased motor activity during active sleep