Sleep in parents of preterm infants: A systematic review

Midwifery 73 (2019) 35–48

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Review Article

Sleep in parents of preterm infants: A systematic review Summer Haddad a,b,∗, Cindy-Lee Dennis a,c, Prakesh S. Shah d,e, Robyn Stremler a,b a

Lawrence S. Bloomberg Faculty of Nursing, University of Toronto, Toronto, Ontario, Canada The Hospital for Sick Children (SickKids), Toronto, Ontario, Canada c Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto, Canada d Department of Pediatrics, Mount Sinai Hospital, Toronto, Ontario, Canada e Department of Pediatrics, University of Toronto, Toronto, Ontario, Canada b

a r t i c l e

i n f o

Article history: Received 24 August 2018 Revised 9 January 2019 Accepted 13 January 2019

Keywords: Infant, premature Intensive care, neonatal Parents Postpartum period Sleep Systematic review

a b s t r a c t Background: Sleep disruption during the first postpartum year is associated with several negative health outcomes including postpartum depression. Such disruption may be a greater issue for parents of preterm neonates, yet literature on this subject has not been critically reviewed. Objective: To synthesize literature on sleep quantity, sleep quality, and factors influencing sleep among parents of preterm infants during infant hospitalization and following discharge. Design: A systematic review. Data sources: Medline, EMBASE, CINAHL, PsycINFO, Scopus, and Cochrane Database of Systematic Reviews were searched from their inception to February 2017. Methods: Potentially eligible citations were reviewed by two independent reviewers. Both quantitative and qualitative studies were eligible for inclusion. Data on eligible studies and review outcomes were extracted using a customized form. Findings: Eighteen reports from 16 studies met inclusion criteria. Four studies included a control group of parents of full-term infants. Three studies reported sleep quantity means, of which only one provided values for an exclusive sample of mothers of preterm infants and found on average, mothers obtained 6.3 h of sleep/day in the first 5–10 days. Twelve studies reported on sleep quality; most (n = 10) relied on selfreported measures and identified poor subjective sleep quality whereas two studies objectively measured sleep of poor quality. Parental stress was the most consistent factor associated with sleep quality. Conclusion and implications: Quality and quantity of sleep among parents of preterm infants is inadequate and may negatively influence family health outcomes. Further research on correlates and changes in sleep is required to identify at-risk parents and inform targeted clinical recommendations and interventions aimed at maximizing sleep for parents of preterm infants. © 2019 Elsevier Ltd. All rights reserved.

Introduction Approximately 15 million infants worldwide are born annually at preterm gestation, defined by the World Health Organization (2012) as less than 37 completed weeks of pregnancy. Many of these neonates require prolonged hospitalization depending on gestational age and medical condition of the newborn. This has been described as a traumatic experience and a significant stressor for many families (Jubinville et al., 2012; Misund et al., 2013). Cohort studies report that when compared to parents of term infants, parents of preterm infants report heightened levels of depression, anxiety and stress (Pace et al., 2016; Vigod et al., 2010). The high

∗ Corresponding author at: Lawrence S. Bloomberg Faculty of Nursing, University of Toronto, 155 College Street, Toronto, Ontario M5T 1P8, Canada. E-mail address: [email protected] (S. Haddad).

https://doi.org/10.1016/j.midw.2019.01.009 0266-6138/© 2019 Elsevier Ltd. All rights reserved.

level of stress and uncertainty can affect parents’ sleep, which in turn, may result in negative implications for parent-child interactions, breastfeeding and health outcomes. There is growing recognition that sleep disruption characterized by decreased sleep quantity and poor sleep quality negatively affects physical health, stress response, cognitive function, memory and mood (Faraut et al., 2012; Stepanski, 2002; Tsuno et al., 2005). In healthy adults, partial sleep deprivation of 5– 6 h has been shown to result in daytime sleepiness and negative mood (Dinges et al., 1997), and when continued for 1–2 weeks can lead to cognitive impairments equivalent to those observed in healthy adults deprived of sleep for 48 h (Van Dongen et al., 2003). Given that preterm infants remain hospitalized for several weeks to months, the potential cumulative effect of poor parent sleep on their ability to retain complex health information and participate in decision-making is of particular concern.

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Evidence is mounting that sleep disruption precedes the development of general depression in men and women (Baglioni et al., 2011), and postpartum depression (PPD) for new mothers (Dennis and Ross, 2005; Lawson et al., 2015). Less is known about effects of sleep disruption among fathers, but available evidence suggests that fathers’ reported poor sleep quality (Hall et al., 2017) and infant sleep problems (Smart and Hiscock, 2007) are associated with paternal PPD symptoms. PPD places children at risk for poor cognitive, behavioural, and emotional development (Beck, 1998; Grace et al., 2003) including those born preterm (Gray et al., 2004; Treyvaud et al., 2010). In addition, maternal sleep disruption in the postpartum period may contribute to the early cessation of breastfeeding (Ball, 2003), bed-sharing behaviours (Tully et al., 2015; Ward, 2014), maternal weight retention (Gunderson et al., 2008) and poor infant attachment (Tikotzky et al., 2012). Studies examining sleep in parents of children hospitalized on general medicine, oncology, and pediatric intensive care units report significant sleep disruption (Franck et al., 2013; McCann, 2008; McLoone et al., 2013; Meltzer et al., 2012; Stickland et al., 2016; Stremler et al., 2014). While some studies suggest parental stress during an infant’s hospitalization is associated with poor sleep (Busse et al., 2013; Lee and Hsu, 2012) other studies report no differences in sleep among parents of preterm and term infants (Gennaro and Fehder, 20 0 0; Hill et al., 20 05). To date, no review has comprehensively evaluated studies examining sleep among parents of preterm infants. Our objective was to systematically review sleep outcomes among parents of preterm infants during infant hospitalization and following discharge with a focus on sleep quantity, sleep quality, and factors influencing sleep.

Studies not reporting primary data such as commentaries, editorials, reviews, letters to editors and opinion pieces were excluded. Conference abstracts, case reports and dissertations were also excluded.

Sleep outcomes Sleep quantity or sleep duration refer to number of hours asleep and are used interchangeably in the literature. We classified both these constructs as sleep quantity in this review. We included any method used for determining number of hours asleep. This included objective measures such as lab-based polysomnography, actigraphy or self-report. Actigraphy, a non-invasive wristworn device, allows collection of objective sleep-wake data in nonlaboratory settings, and therefore can be used to assess parents’ sleep at home and in hospital (Ancoli-Israel et al., 2003). Sleep quality was conceptualized as subjective perceptions of sleep, such as perceived depth and restfulness, as well as quantifiable proxies of quality (e.g. wake time during the night) and can be measured objectively or by self-report (Buysse et al., 1989). Given the broad use of the term sleep quality in the literature, all studies examining numerical quality parameters and subjective reports were included.

Data extraction

We followed the Cochrane Handbook for Systematic Reviews (Higgins and Green, 2011) guideline in the conduct of this review and reported using the frameworks of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement (Moher et al., 2015).

All study details and sleep outcome data were independently extracted using a customized form and checked by another reviewer for accuracy. Multiple papers reporting on the same sample were retained if they reported on unique variables that contributed to answering any of the three objectives. If multiple papers reported data from the same variables, only variables from the earliest published paper were retained during extraction. Papers published from the same sample are indicated in wording/notation throughout this review

Search strategy

Quality assessment and risk of bias

Five electronic databases (MEDLINE, Embase, CINAHL, PsycINFO, Scopus) and the Cochrane Database of Systematic Reviews were searched from their inception through February 2017 with librarian assistance. No date restrictions were placed in order to get a better sense of the current state of research on this topic. The main search terms were relevant to parent, mother, father, sleep, prematurity, neonatal intensive care and were modified according to database requirements. The full search strategy is provided in supplementary files. Titles and abstracts were screened for relevance. Potentially eligible citations were retrieved in full-text and assessed for eligibility by two independent reviewers. The reference lists of included studies were hand searched to identify additional articles.

To assess the quality of quantitative studies with diverse designs, a tailored checklist (provided in supplementary files) was adapted from the Effective Public Health Practice Project Quality Assessment Tool (Thomas et al., 2004) and a review article published on quality assessment tools (Sanderson et al., 2007). Studies were rated on 5 criteria using a 3-point scale (low, moderate, high risk of bias), including sample selection, defined sample, comparability/confounding, data collection methods, and withdrawal/follow-up. Determination of risk of bias ratings for each study was completed independently by two reviewers. Following individual appraisal, an overall rating was given. A study was deemed as having “low risk of bias” if no criteria received a high risk of bias rating, “moderate risk of bias” if only one criteria received a high risk of bias rating and “high risk of bias” if two or more criteria were rated high risk. Qualitative studies were assessed for risk of bias using the Critical Appraisal Skills Programme (CASP) tool (CASP, 2013). A score out of 10 was allocated for each qualitative article based on how many questions were answered as “yes, key features present”. Other systematic reviews have considered a score of seven or more to indicate ‘very good’ quality (Vanderspank-Wright et al., 2018). Given the aim of this review was to examine the state of published literature on this topic, no studies were excluded based on risk of bias assessment. Any discrepancies among the two reviewers were resolved by discussion and consensus with a third reviewer.

Methods

Selection criteria Studies were considered eligible for inclusion if they met the pre-defined criteria: 1) reported primary data on parents’ sleep; 2) specified the number of parents (mother, father, step-parent foster parent) of preterm infants within their total sample; 3) included >50% of parents of preterm infants in the sample when both parents of term and preterm infants were included in the study; and 4) reported on sleep outcome data within first postpartum year. All designs, including quantitative and qualitative studies, were eligible for inclusion. Only English language articles were included.

S. Haddad, C.-L. Dennis and P.S. Shah et al. / Midwifery 73 (2019) 35–48

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Fig. 1. Study selection diagram.

Analyses We planned to perform a meta-analysis of available data reporting sleep quantity and sleep quality using fixed-effects model or random-effects model based on assessment of heterogeneity. Clinical and methodological heterogeneity was evaluated using study characteristics and study design. Statistical heterogeneity was planned to be evaluated using I2 statistic where value of <25% indicates low variation, and >50% indicates moderate to high variation due to heterogeneity across studies (Higgins et al., 2003). However, substantial clinical and methodological heterogeneity in study designs, measurement tools and timing of sleep assessments precluded meta-analyses. Narrative synthesis was completed, and findings are presented in summary tables.

Results A total of 1912 citations were retrieved from the database searches, one additional eligible article was identified by hand searching of retrieved articles (Lee et al., 2007). After applying exclusion criteria, 30 articles were retrieved for detailed review from which a further 12 were excluded. Six studies were excluded because they did not report primary data on parents’ sleep (Affleck et al., 1986; Boyle et al., 1977; Bryanton and Beck, 2010; Geetanjli et al., 2012; Heinemann et al., 2013; Wraight et al., 2015), two did not specify the number of parents who had a preterm birth in their samples (Parfitt and Ayers, 2014; Vilska and Unkila-Kallio, 2010), and one study assessed parents’ sleep when the preterm infant was >1 year of age (Biggs et al., 2016). Three studies were excluded for sample overlap and lack of unique data pertaining to the review aims (Gennaro et al., 1997; Lee et al., 2013; Lee and

Kimble, 2009). Overall, 18 articles, reporting on 16 unique studies were included in the review (Fig. 1). Characteristics of included studies Characteristics of included studies are reported in Table 1. Of the 16 included studies, one was a randomized controlled trial (Karbandi et al., 2015), one was an intervention case series (Schaffer et al., 2013), six were prospective cohort studies, (Blomqvist et al., 2017; Gennaro et al., 1992; Gennaro and Fehder, 20 0 0; Hill et al., 2005; McMillen et al., 1993; Williams and Williams, 1997), six cross-sectional studies (Busse et al., 2013; Henderson et al., 2016; Lee et al., 2007; Lee, 2012; Lee and Lee, 2007; Lee and Hsu, 2012; Nordheim et al., 2016; Zamanzadeh et al., 2013b), two were qualitative studies, of which one was descriptive (Zamanzadeh et al., 2013a) and the other used phenomenological methodology (Edéll-Gustafsson et al., 2015). Eight studies were conducted in the United States (Busse et al., 2013; Gennaro et al., 1992; Gennaro and Fehder, 20 0 0; Hill et al., 20 05; Lee et al., 20 07; Lee, 2012; Lee and Lee, 20 07; Lee and Hsu, 2012; Schaffer et al., 2013; Williams and Williams, 1997), three in Iran (Karbandi et al., 2015; Zamanzadeh et al., 2013b, 2013a), two in Sweden (Blomqvist et al., 2017; Edéll-Gustafsson et al., 2015), and one study each in the UK (Henderson et al., 2016), Australia (McMillen et al., 1993), and Norway (Nordheim et al., 2016). Four studies compared sleep among parents of preterm infants and those of healthy, term infants (Gennaro and Fehder, 20 0 0; Henderson et al., 2016; Hill et al., 2005; McMillen et al., 1993). Three studies reported sleep outcomes for parents of mixed samples of preterm and term newborns (Busse et al., 2013; EdéllGustafsson et al., 2015; Lee et al., 2007). Three studies focused exclusively on parents of infants of gestational age < 32 weeks and

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Table 1 Characteristics of included studies.

Study design

PP Participants (N, site)

PHT Control Participants

Gennaro et al., 1992 (USA)

Prospective survey

N = 60 mothers Single-site

N/A

McMillen et al., 1993 (Australia)

Prospective cohort

N = 22 mothers Single-site

N = 23 mothers Site: NR

Williams and Williams, 1997 (USA)

Prospective survey

N/A

Sleep: VSH- sleep effectiveness Other: MAF, PSS-10 item, FCOPES, FACES II, Neonatal Morbidity Scale

Gennaro and Fehder, 20 0 0 (USA)

Prospective matched cohort

Total N = 74 mothers Group 1: N = 28 infants on apnea monitor Group 2: N = 46 infants no apnea monitor Multi-site: 3 sites N = 64 mothers VLBW infants (<1500 gm) Multi-site: 3 sites

Hill et al., 2005 (USA)

Prospective cohort

N = 95 mothers (infant <37 weeks) Multi-site: 4 sites

N = 60 mothers (matched on age, parity, race, SES) Multi-site: 3 hospitals N = 98 mothers Multi-site: 4 tertiary centers

Lee and Lee, 2007 (USA)†

Cross-sectional

N = 21 mothers of infants in hospital (11 preterm, 10 term) Multi-site: 3 sites

Lee et al., 2007 (USA)†

Cross-sectional

Lee et al. 2012 (USA)††

Cross-sectional

Lee and Hsu, 2012 (USA)††

Cross-sectional

N = 55 parents (30 mothers; 25 fathers) N/A 30 infants (16 preterm 14 term) Multi-site: 3 sites N = 51 mothers N/A Group 1: N = 25 low activity Group 2: N = 26 high activity Multi-site: 3 sites N = 55 mothers of preterm infants N/A Multi-site: 3 sites

Busse et al., 2013 (USA) Cross-sectional

Edéll-Gustafsson et al., 2015 (Sweden)

Qualitative

N = 30 (22 mothers, 8 fathers); 28 preterm (<39 weeks), 2 term infants Single-site N = 12 parents (8 mothers and 4 fathers) of 8 infants (7 preterm and 1 term) Multi-site: 3 sites

N/A

N/A

N/A

Timing of sleep assessment and infant location

Parent sleep location

Quality Assessment

Timing: One week following delivery, discharge, monthly from 1–6 months Location: hospital/ at home Timing: Every 1–2 weeks after birth (term) or discharge (preterm); followed for 5 months Location: hospital/ home Timing: Discharge, 1 week, 1 month post-discharge (postnatal age NR) Location: hospital/ home

NR

High

Hospital at delivery; home after discharge

High

NR

Moderate

Sleep: SWAI (sleep log), Other: SSS, Timing: 24hours after delivery, 1, 2, 4 24-hour diet recall, FWPA, blood serum months postpartum (cotinine; caffeine) Location: hospital/ home

NR

High

Timing: After birth, daily for 6 weeks Sleep: RCSQ Other: PSS-VAS, Fatigue Scale-VAS, EBM Location: hospital/home (75% of volume log preterm infants in hospital for duration) Timing: 3–5 days postpartum Sleep: Actigraphy (48 h) GSDS Location: hospital Other: 7-item NRS-F

NR

Moderate

C/S mothers slept in hospital; SVD mothers slept at home Mixed; # NR

Moderate

Low

Measures Sleep: Structured telephone interviews (recorded as increase, decrease, no change, uncertain) Sleep: 24-hr sleep diary Other: saliva for melatonin/ cortisol

Sleep: Actigraphy (48 h), GSDS Other: 7-item NRS-F, PSS: IH

Timing: 3 days- 1year postnatal age Location; hospital

Sleep: Actigraphy (48–72 h), GSDS Other: CAR- LFS, EPDS, SF36v2

Timing: 5–10 days postpartum Location: hospital

Home

Moderate

Sleep: Actigraphy (48–72 h), GSDS 6-item Other: PSS-10 item IES, Lee’s Fatigue Scale, EPDS, SF36v2 Sleep: PROMIS subscale Other: PROMIS-fatigue, anxiety, depression scales, PSS: NICU Sleep: Semi-structured interviews

Timing: 5–10 days postpartum Location: hospital

Home

Moderate

Timing: LOS M(SD)=24.66 (27) (range 4–110 days) Location: In hospital Timing: 7–46 days postpartum Location: hospital

NR

Low

Hospital

7 CASP

(continued on next page)

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Author, year, country

Table 1 (continued) Study design

PP Participants (N, site)

PHT Control Participants

Measures

Timing of sleep assessment and infant location

Karbandi et al., 2015 (Iran)

RCT

N/A

Sleep: PSQI Other: intervention use log

Timing: Baseline (24–72 h postpartum) NR 4, 8 weeks postpartum Location: hospital

High

Schaffer et al., 2013 (USA)

Case-series of intervention

N = 60 mothers (infants 32–36 weeks GA) Group 1: N = 30 intervention Group 2: N = 30 control group Multi-site: 3 sites n = 20 mothers (Infant <33 weeks) Single-site

N/A

Timing: Baseline, at week 8 NR post-intervention (postpartum day NR) Location: hospital

Low

N = 16 mothers (infant <37 weeks) Multi-site; # NR

N/A

Sleep: PSQI Other: CES-D, STAI-state, PSS-10 item, Functional Social Support Questionnaire, Maternal Health History, Neonatal Medical Index Sleep: semi-structured interviews

NR

4 CASP

N = 120 fathers of infants (<37 weeks) Multi-site: # NR

N/A

Sleep: AGQ "difficulty sleeping" item Other: AGQ items

NR

Moderate

N = 285 mothers of infant <37weeks Group 1: n = 42 (<32 weeks) Group 2: n = 243 (32-<37 weeks) Site: Random selection; England birth registry N = 61 (32 mothers, 29 fathers of preterm infants <1500 gm) Multi-site: 3 sites

N = 4293 mothers of term infant (≥37 weeks) Site: Random selection; England birth registry

Sleep: Investigator developed sleep problem item Other: EPDS, investigator developed checklists

Timing: Prior to discharge. LOS range (1 week-2 months) Location: hospital Timing: LOS M (SD): 6.09 (9.96) (Range, 1–20 days) (postnatal age NR) Location: hospital Timing: 3 months postpartum Location: majority (99.7%) home

NR

Moderate

N/A

N = 170 (86 mothers, 84 fathers) of 86 infants (<34 weeks) Multi-site: 2 sites

N/A

Sleep: GSDS Other: QoLS-N, HADS, Lee Fatigue Scale, Self-Administered Comorbidity Questionnaire, Stressful Likert Scale Sleep: ISI, investigator-developed sufficient sleep item Other: perception of infant sleep/ location

Zamanzadeh, Qualitative Namnabati et al., 2013a (Iran) Zamanzadeh, Valizadeh Cross-sectional et al., 2013b (Iran) Henderson et al., 2016 (England)

Cross-sectional (Populationbased survey)

Nordheim et al., 2016 (Norway)

Cross-sectional

Blomqvist et al., 2017 (Sweden)

Prospective survey

Parent sleep location

Quality Assessment

Timing: Retrospective sleep assessment NR during hospital when infant 3.5 years Location: home

High

Timing: During hospitalization, infant 2 Mixed: # NR months and 12 months CA Location: hospital/home

High

AGQ, Anticipatory Grief Questionnaire (Likert), CAR, Circadian activity level; CASP, Critical Appraisal Skills Programme; CES-D, Center for Epidemiological Studies-Depression Scale; C/S, Caesarian Section; EBM, Expressed Breast Milk; EPDS, Edinburgh Postnatal Depression Scale; FACES-11, Family Adaptability and Cohesion Scale; FCOPES, Family Crisis Oriented Personal Evaluation Scale; FWPA, Four-Week Physical Activity Questionnaire; GSDS, General Sleep Disturbance Scale HADS, Hospital Anxiety and Depression Scale; IES, Impact of Event Scale; IQR, Interquartile Range, ISI, Insomnia Severity Index; LFS, Lee’s Fatigue Scale; LOS, Length of Stay (days); M, Mean; MAF, Multidimensional Assessment of Fatigue; N/A, Not applicable; NR, Not reported; NRS-F, Numerical Rating Scale for Fatigue; PHT, Parents of Healthy, Term Infants; PP, Parents of Preterm Infants; PROMIS, Patient Reported Outcomes Measurement Information System; PSQI, Pittsburgh Sleep Quality Index; PSS: Perceived Stress Scale (10 items); PSS:IH, Parental Stressor Scale: Infant Hospitalization; PSS:NICU, Parental Stressor Scale (PSS): Neonatal Intensive Care Unit; PSS:VAS, Perceived Stress Scale: Visual Analogue Scale; QoLS-N, Quality of Life Scale-Norwegian version; SD, Standard Deviation; SES, Socio-Economic Status; SF-36v2, Short-form health survey version 2; SSS, Stanford Sleepiness Scale; STAI, State- Trait Anxiety Inventory; SVD, Spontaneous vaginal delivery; SWAI, Sleep-Wake Activity Inventory (sleep log); RCSQ, Richards-Campbell Sleep Questionnaire; VSH, Verran and Snyder-Halpern Sleep Scale; VLBW, Very low-birth weight. † Lee & Lee (2007) (n = 21) and Lee et al. (2007) (n = 55) include participants from same sample. Studies included as they reported data uniquely contributing to answering any one of the three objectives. Only unique outcomes were retrained during extraction and will be reported in subsequent tables. †† Lee & Hsu (2012) (n-=55) and Lee et al. (2012) (n = 51) include participants from the same sample. Studies included as they reported data uniquely contributing to answering any one of the three objectives. Only unique outcomes were retrained during extraction and will be reported in subsequent tables.

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Author, year, country

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S. Haddad, C.-L. Dennis and P.S. Shah et al. / Midwifery 73 (2019) 35–48

Table 2 Sleep quantity outcomes in parents of preterm infants.

Study

Sleep Quantity Measure; outcome reported

Timing

Preterm Group

One week following delivery, at discharge 55% (n = 33) mothers reported less sleep and monthly for 6 months CA at one month than at time of discharge 35–40% (n = 20–25) report no change in sleep across monthly measurements from 3–6 months. McMillen et al. (1993) 24-hour sleep diary;% Every 1–2 weeks after birth of term NR of time asleep in 24 h infant or discharge home of preterm infant until 5 months postpartum (term) or 5 months post-discharge (preterm) Gennaro and Sleep-diary (length of Within 24 h after delivery, at 1, 2, 4 NR Fetime NR); hours asleep months Pooled preterm/term sample: hder (20 0 0) in 24 h Following delivery: M (SD)=6.0 (2.2)∗ One month: M (SD)= 6.7 (2.06)∗ Two months: M (SD)= 7.1 (2.8)∗ Four months M (SD)=7.1 (1.8)∗ Lee et al. (2007)† Actigraphy (48 h); During hospitalization (infant 3 days- 1 Mixed sample: hours asleep in 24 h year old) Overall parent M = 6.3 (hand-calculated)∗ Mothers M = 6.1 SEM=15.3 (min)∗ Fathers M = 6.6 SEM=16.5 (min)∗ Lee and Hsu (2012)†† Actigraphy (48–72 h); At 5–10 days postpartum M (SD) = 6.3 (1.75) hours asleep in 24 h Gennaro et al. (1992)

Telephone interviews; sleep as increase, decrease or no change

Term Group Test of Differences N/A

N/A

NR

(≤.05) ∗ mothers of preterm infant slept less% of day

NR

NS (p = 0.06)

N/T

N/A

N/A

M, mean; N/A. not applicable, NS, not significant; N/T, not tested, SD, standard deviation; SEM, standard error of mean. ∗ mixed or pooled preterm/term sample data. † Lee & Lee (2007) (n = 21) and Lee et al. (2007) (n = 55) include participants from same sample. Lee and Lee (2007) sleep quantity means/ SD via actigraphy not reported. †† Lee and Hsu (2012) (n-=55) and Lee et al. (2012) (n = 51) include participants from the same sample. Lee et al. (2012) sleep quantity means/SD via actigraphy not reported.

birth weight <1500 g (Gennaro and Fehder, 20 0 0; Nordheim et al., 2016; Schaffer et al., 2013) and one study completed a subgroup analysis of three groups (<32, 32–36, >37weeks) (Henderson et al., 2016). Ten studies included only mothers, five included mothers and fathers (Blomqvist et al., 2017; Busse et al., 2013; EdéllGustafsson et al., 2015; Lee et al., 2007; Nordheim et al., 2016) and one reported a sample only of fathers (Zamanzadeh et al., 2013b). Sample sizes of quantitative studies varied considerably, ranging from 20 (Schaffer et al., 2013) to 528 mothers of preterm infants (Henderson et al., 2016). One article reported on a populationbased, randomly selected sample (Henderson et al., 2016), four recruited from a single-site (Busse et al., 2013; Gennaro et al., 1992; McMillen et al., 1993; Schaffer et al., 2013), and the remainder reported recruiting from multiple sites. In relation to sleep assessment timing, 10 studies reported on parents’ sleep during the infant’s hospitalization. Data were collected either at time of hospitalization (Busse et al., 2013; EdéllGustafsson et al., 2015; Karbandi et al., 2015; Lee et al., 2007; Lee, 2012; Lee and Lee, 2007; Lee and Hsu, 2012; Schaffer et al., 2013; Zamanzadeh et al., 2013a, 2013b) or retrospectively (Henderson et al., 2016; Nordheim et al., 2016). The majority of studies did not report parents’ sleep location with only one study reporting that all parents slept in hospital (in the same room as infant or in nearby room) (Edéll-Gustafsson et al., 2015), while another indicated that parents slept at home (Lee and Hsu, 2012). Six studies reported parent sleep following infant’s hospital discharge (Blomqvist et al., 2017; Gennaro et al., 1992; Gennaro and Fehder, 20 0 0; Hill et al., 2005; McMillen et al., 1993; Williams and Williams, 1997). Lee and colleagues reported on objectively measured sleep using actigraphy (Lee et al., 2007; Lee, 2012; Lee and Lee, 2007; Lee and Hsu, 2012). Other studies assessed parent-reported sleep using diary data or validated questionnaires, including the Pittsburgh Sleep Quality Index (PSQI), General Sleep Disturbance Scale (GSDS), Insomnia Severity Index (ISI), Richards-Campbell Sleep Questionnaire (RCSQ), and Patient Reported Outcomes Measurement Information System (PROMIS) (Blomqvist et al., 2017; Busse et al.,

2013; Hill et al., 2005; Karbandi et al., 2015; Schaffer et al., 2013; Williams and Williams, 1997). Other studies did not use validated tools for the measurement of parent-reported sleep (Gennaro et al., 1992; Gennaro and Fehder, 20 0 0; Henderson et al., 2016; McMillen et al., 1993; Nordheim et al., 2016; Zamanzadeh et al., 2013b). Methodological quality assessment The overall methodological quality of studies was mixed as shown in Table 1. (See supplementary files for domain specific assessment of quantitative and qualitative studies). Of 16 quantitative articles, six articles were at high risk of bias, seven at moderate risk and three articles received an overall low risk of bias rating. Methodological limitations of quantitative studies included selection bias and selective reporting. Many studies were cross-sectional with descriptive aims which limited assessment of confounders and attrition. The two qualitative studies received an overall four (Zamanzadeh et al., 2013a) and seven (Edéll-Gustafsson et al., 2015) total score rating on the CASP. Despite providing some description of methods of analyses, explicit discussion regarding data saturation, contradictory findings, respondent validation, and reflexivity in regards to researcher-participant relationship was not detailed (CASP, 2013). Outcomes 1 Sleep quantity Five studies (7 publications) provided information on sleep quantity for parents of preterm infants (Table 2). Three studies reported on self-report sleep quantity (Gennaro et al., 1992; Gennaro and Fehder, 20 0 0; McMillen et al., 1993), and two studies reported on objective measures of sleep (Lee et al., 2007; Lee and Hsu, 2012). The quantity of hours of sleep achieved in a 24-hour period (total sleep time) was reported in three studies. However, two of these studies reported sleep quantity means for mixed samples of parents of preterm and term infants (Gennaro and Fe-

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hder, 20 0 0; Lee et al., 2007) (Table 2). Only the study by Lee and Hsu (2012) provided objectively measured sleep quantity for an exclusive sample of mothers of preterm infant (n = 55), reporting an average sleep time of 6.3 h/24 h (SD=1.75) at 5–10 days postpartum. All mothers slept at home while their infant remained hospitalized during the study period. Two longitudinal studies compared sleep quantity for mothers of preterm and term infant controls using sleep diary data. One U.S. study (Gennaro and Fehder, 20 0 0) of 124 mothers, reported no differences in sleep quantity between mothers of very low birthweight infants and mothers of term infants (p = 0.06). In a smaller sample of 55 mothers, McMillen et al. (1993) reported that mothers of preterm infants had less sleep time than mothers of term infants over 5 months post-partum (p<0.05). Studies are limited due to the lack of reporting of individual group means. 1 Sleep quality Twelve studies reported on parent sleep quality (see Table 3). Three longitudinal studies compared sleep quality reported by mothers of preterm and term infants using sleep diaries. Studies by Gennaro and Fehder (20 0 0) and Hill et al. (2005) had mothers of preterm and term infants report on their sleep over 6 weeks or until 4 months corrected infant age and found no difference in reported sleep quality at any time-point. McMillen et al. (1993) identified that mothers of preterm infants (n = 22) reported significantly more time awake at night than mothers of term infants (n = 23) in the 5 months following delivery or discharge. However, means were provided according to parity and specific p-values and overall group differences were not reported (McMillen et al., 1993). Two studies reported on objective proxies of sleep quality measures obtained using wrist-actigraphy. However, only Lee and Hsu (2012) provided objective data on an exclusive sample of mothers of preterm infants (n = 55) reporting 96 min (SD=65) of wake time during the night and sleep efficiency (percentage of time asleep to time in bed) of 80.5% (SD=11.2) at 5–10 days postpartum. Importantly, all mothers slept at home while their infant remained hospitalized, and reason for being awake (e.g. breastmilk expression, other children) were not reported (Lee and Hsu, 2012). Studies using established, validated sleep quality questionnaires (PSQI, GSDS, PROMIS) reported scores indicative of poor sleep quality (Busse et al., 2013; Karbandi et al., 2015; Lee et al., 2007; Lee and Hsu, 2012; Schaffer et al., 2013). One Swedish study that examined insomnia using the Insomnia Severity Index (ISI), reported mild to no symptoms of insomnia among mothers and fathers at time of hospitalization to 12 months corrected infant age (Blomqvist et al., 2017). Studies at high risk of bias utilized retrospective recollection of parent sleep quality and single-sleep items. High risk of bias studies reported low proportions of problematic sleep among parents of preterm infants (Henderson et al., 2016; Nordheim et al., 2016) and no differences in the proportion of mothers of preterm and term infants reporting problematic sleep (Henderson et al., 2016). 1 Factors influencing parent sleep

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privacy, nose-level) was qualitatively reported as impacting parent sleep (Edéll-Gustafsson et al., 2015; Zamanzadeh et al., 2013b). Parent/family characteristics Two studies examined sociodemographic variables (e.g. parent age, ethnicity, education, income) and sleep quality, and results were inconclusive. Schaffer et al. (2013) reported that older maternal age and household income >$30, 0 0 0 USD were associated with better sleep quality on the PSQI. Two studies compared sleep quality for mothers and fathers; one of which reported mothers had significantly worse objective sleep quality (higher fragmentation) and poorer self-reported sleep compared to fathers (wake time after sleep onset 17% vs. 7%; GSDS 51.2 vs. 36.9; p<0.05) (Lee et al., 2007). In contrast, Blomqvist et al. (2017) reported no gender differences in parents’ insomnia severity Higher levels of perceived support was associated with better sleep quality on PSQI in sample of 20 mothers (Schaffer et al., 2013). Parity and marital status were uncommonly assessed, but predominately found to not be associated with self-reported sleep quality (Busse et al., 2013; Gennaro and Fehder, 20 0 0; Schaffer et al., 2013). Parent stress, anxiety, depression Of the six quantitative studies investigating stress in relation to sleep (Busse et al., 2013; Hill et al., 2005; Lee et al., 2007; Lee and Hsu, 2012; Schaffer et al., 2013; Williams and Williams, 1997), four identified a significant negative relationship between parent stress related to their infant’s hospitalization (PSS: NICU) (Busse et al., 2013) or general stress (Hill et al., 2005; Lee and Hsu, 2012; Williams and Williams, 1997) and reported sleep quality. Lee and colleagues examined stress in relation to objective sleep quantity during hospitalization and reported a significant negative correlation for fathers(r=−0.62; p< 0.01) but no difference for mothers (Lee et al., 2007; Lee and Hsu, 2012). Qualitative interviews suggest opportunities for parent involvement in infant care may reduce stress and improve sleep (Edéll-Gustafsson et al., 2015; Zamanzadeh et al., 2013a). Two small U.S-based studies quantitatively investigated the impact of generalized anxiety level and parent sleep quality (Busse et al., 2013; Schaffer et al., 2013). In Busse et al. (2013) sample of 30 parents, higher anxiety on PROMIS was associated with worse sleep quality, but no association was found between the STAI-state subscale and PSQI in Schaffer et al. (2013) sample of 20 mothers. Depression has been linked to poor sleep quality in other perinatal populations. Of the three studies that examined depression and sleep quality, all reported on parent sleep and depressive symptoms during infant hospitalization. Two small U.S-based studies (n = 20 to 30 parents) reported positive associations between depressive symptoms and worse self-reported sleep quality on PROMIS questionnaire (r = 0.45; p< 0.05) (Busse et al., 2013) and PSQI (r = 0.496; p = 0.026) (Schaffer et al., 2013). In a slightly larger sample of 55 mothers of preterm infants no association between depressive symptomology using the EPDS and any self-report or objective sleep measure were identified in the first 5–10 days postpartum (Lee and Hsu, 2012).

Ten articles reported on factors associated with parent sleep quantity and quality (see Table 4).

Discussion

Hospital/infant characteristics Delivery method, breastfeeding, infant illness severity, and hospital visiting were not associated with sleep quantity or quality (Busse et al., 2013; Hill et al., 2005; Lee and Lee, 2007; Lee and Hsu, 2012; Schaffer et al., 2013). Only one study examined parent sleep location and insomnia severity (ISI), reporting no differences among Swedish parents provided overnight sleep accomodation at infant hospital bedside and those not provided sleep accomodation (Blomqvist et al., 2017). The hospital environment (e.g.

In this systematic review of sleep outcomes of parents of preterm infants, we identified 16 studies of low to high risk of bias. Parents of preterm neonates reported less than the recommended hours of sleep while their neonate was in-hospital as well as during the first few months after discharge. Parent-reported and objective proxies of sleep quality were indicative of highly fragmented, poor sleep quality. Among factors evaluated for association with poor sleep, parenting stress was the most consistent factor identified to be correlated with poor sleep. Significant clini-

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Table 3 Sleep quality outcomes in parents of preterm infants. Study

Sleep quality measure

Timing

Preterm group

Term Group

Test of Differences

McMillen et al. (1993)

Sleep diary; % WASO

Every 1–2 weeks after birth (term) or discharge (preterm); follow-up for 5 months

Sleep diary; # of awakenings/night RCSQ; sleep quality

NS

NR

NR

NS (p = 0.334)

Lee et al. (2007)†

Actigraphy;% WASO

Within 24 h after delivery, 1, 2, 4 months After delivery; daily until 6 weeks postpartum During hospitalization

Overall M(SD) NR Primiparous M (SD)=36% (5%) Second child M (SD)=30% (2%) Third child M (SD)=30% (2%) M = 1(SD NR)

Significant (p-value NR);%WASO higher in preterm group

Gennaro and Fehder (20 0 0) Hill et al. (2005)

Overall M(SD) NR Primiparous M (SD)=41% (5%) Second child M (SD)=36% (4%) Third child M (SD)=37% (5%) M = 1 (SD NR)

21-item GSDS

During hospitalization

Actigraphy;%WASO/ WASO (min)

5–10 days postpartum

Infant 3.5 years of age During hospitalization, 2 months CA, 12 months CA

6-item GSDS Busse et al. (2013)

PROMIS

During hospitalization (LOS 4–110 days)

Schaffer et al. (2013)

PSQI

Baseline (postpartum day NR)

Zamanzadeh et al. (2013b) Karbandi et al. (2015)

Sleep item Anticipatory Grief Questionnaire PSQI

During hospitalization (LOS 1–20 days) During hospitalization (24–72 h postpartum)

Investigator developed question “Sleep problem not related to baby” @ 10 days, 1, 3 months (%, n) GSDS (retrospective; during hospitalization) ISI

Infant 3 months of age

Henderson et al. (2016)

Nordheim et al. (2016) Blomqvist et al. (2017)

N/T

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

Term 10 days:5.8%, n = 239 1 month 2.8%, n = 200 3 months: 4.2%, n = 175

NS

GSDS M = 38 (hand-calculated)

N/A

N/A

Hospitalization: Maternal Median=8 (range 0–26) Paternal Median 6 (range 0–22) 2 months CA: Maternal Median=5 (range NR) Paternal Median=4 (range NR) 12 months CA: Maternal ISI: Median=7 (range NR) Paternal ISI: Median=5 (range NR)

N/A

N/A

CA, corrected age; GSDS, General sleep disturbance scale; ISI, Insomnia Severity Index; LOS, Length of stay, M, mean; NR, not reported; NS, Not significant; PROMIS, Patient Reported Outcomes Measurement Information System; PSQI, Pittsburgh Sleep Quality Index; SD, standard deviation; SEM, standard error of mean; RCSQ, Richards-Campbell Sleep Questionnaire; WASO, wake time after sleep onset, VAS, Visual Analogue Scale. ∗ mixed or pooled preterm/term sample data. † Lee and Lee (2007) (n = 21) and Lee et al. (2007) (n = 55) include participants from same sample. Lee and Lee (2007) sleep quality means (SD) via actigraphy/GSDS will not be reported. †† Lee and Hsu (2012) (n-=55) and Lee et al. (2012) (n = 51) include participants from the same sample. Lee et al. (2012) sleep quality data via actigraphy/ GSDS will not be reported.

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Lee and Hsu (2012)††

Overall Parent%WASO M = 12.5%∗ (hand-calculated) Maternal M = 17% SEM=2.6∗ Paternal M = 7% SEM=1.3∗ Overall Parent GSDS M = 44.7 (hand-calculated); Maternal M = 51.2 (SEM NR) Paternal M = 36.9 (SEM NR) % scoring >43 (cut-off indicating poor sleep quality) NR %WASO M = 20 (12) WASO (min) M (SD)= 96 (65) Sleep efficiency% M (SD)= 80.5 (11.2) GSDS M (SD)=3.5 (1.7); 58% scored >3 (indicating poor sleep quality) M (SD)=17.17 (6.26)∗ 40% (n = 12) parents scored 1–2 SD above U.S. population mean M (SD)=9.79 (3.94) (Range 4–17) % scoring > 5 (cut-off indicating poor sleep quality) NR 35.8% (n = 43) of fathers report moderate/major problem with sleep Overall M = 11.47 (hand-calculated) Control group M (SD)= 11.11 (0.56) Treatment group M (SD) = 11.82 (0.74) Extremely preterm Late preterm 10 days: 7.3%, n = 3 10 days:5.8%; n = 14 1 month 5.8%, n = 14 1 month: 7.3%, n = 3 3 months: 3.1%, n = 5 3 months: 2.4%, n = 1

Table 4 Factors associated with sleep in parents of preterm infants. Factor/Variable

Family variables Parity Marital status Family Cohesion Social Support

Hospitalization and infant variables Preterm illness severity /LOS Distance from hospital Parent-reported time on unit/ # of hospital visits Delivery method (C-section or vaginal) Sleep location Infant feeding (breastfeeding/formula)

Association

No association

Older maternal age associated with better sleep quality (PSQI) (r=−0.488, p = 0.029) (Schaffer et al., 2013) Household income >$30, 0 0 0 associated with better sleep quality on PSQI (r=NR; p = 0.026) (Schaffer et al., 2013) Mothers report worse sleep quality on 21-item GSDS (M = 51.2, SD=NR) than fathers (M = 36.9; SD=NR) (p< 0.05) (Lee et al., 2007)∗ Mothers had objectively higher% WASO (M = 17% SEM=2.6) than fathers (M = 7% SEM=1.3) (p = 0.01) (Lee et al., 2007)∗

NS difference in sleep quality on PROMIS based on parent age (Busse et al., 2013) NS difference in sleep quality on PSQI/PROMIS based on ethnicity; majority Caucasian (Busse et al., 2013; Schaffer et al., 2013) NS difference in sleep quality on PSQI/PROMIS based on education (years) (Busse et al., 2013; Schaffer et al., 2013) NS difference in insomnia severity on ISI or perception of sufficient sleep between mothers and fathers (Blomqvist et al., 2017)

Higher support on Functional Social Support Questionnaire associated with better sleep quality on PSQI (r=−0.462, p = 0.04) (Schaffer et al., 2013)

NS difference in self-reported sleep quantity on sleep diary after delivery, 1, 2,4 months based on parity (Gennaro and Fehder, 20 0 0) NS difference in sleep quality on PSQI/PROMIS/ self-reported number of night-awakenings on sleep diary based on parity (Busse et al., 2013; Gennaro and Fehder, 20 0 0; Schaffer et al., 2013) NS difference in sleep quality on PSQI based on marital status (Schaffer et al., 2013) NS difference on VSH-sleep effectiveness based on family cohesion after controlling for stress, family cohesion, reframing, fatigue, use of apnea monitor in path analysis (Williams and Williams, 1997)

Qualitatively in one-on-one interviews, parents reported that the hospital environment (e.g. privacy, noise-level, temperature) impacted their sleep (Edéll-Gustafsson et al., 2015; Zamanzadeh et al., 2013a)

NS difference in sleep quality on PSQI/PROMIS based on preterm illness severity/LOS (Busse et al., 2013; Schaffer et al., 2013) NS difference in sleep quality on PROMIS based on distance of parent home from hospital (Busse et al., 2013) NS difference in sleep quality on PROMIS based on parent-reported hospital visiting (Busse et al., 2013) NS difference in objectively measured sleep quantity or proxies of sleep quality, or 6-item GSDS in second week postpartum (Lee and Hsu, 2012) NS difference in sleep quality on 21-item GSDS score at 48 h postpartum based on delivery (p>0.05) (Lee and Lee, 2007)† NS differences in insomnia severity on ISI or perception of sufficient sleep based on unit (home vs. hospital sleep) (Blomqvist et al., 2017) NS difference in sleep quality on PSQI based on infant feeding method (Schaffer et al., 2013) NS difference in sleep quality on RCSQ based on feeding method at 6 weeks (Hill et al., 2005)

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Parent demographics Age Ethnicity SES Gender

(continued on next page)

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Table 4 (continued) Factor/Variable Lifestyle Caffeine intake Activity

Anxiety

Depression

No association

Mothers with low activity levels had more daytime sleep quantity M (SD)= 92 min (10) than high activity mothers, M (SD)=49 min (16) (p< 0.05) (Lee et al., 2012)†† Low activity mothers had less%WASO M (SD)=16.3 (9.2) than high activity mothers M(SD)= 23.3 (14.2) (p< 0.05) (Lee et al., 2012)††

NS differences in sleep quantity on sleep diary based on maternal caffeine intake (Gennaro and Fehder, 20 0 0)∗ NS difference in sleep quality on 21-item GSDS based on maternal activity level (Lee et al., 2012)†† NS difference in TST-T (min) based on activity (Lee et al., 2012)††

Stress on PSS:NICU associated with worse sleep quality on PROMIS (r = 0.6; p< 0.01) (Busse et al., 2013) Stress on PSS:VAS associated with worse sleep quality on RCSQ (r = 0.391–0.611, p< 0.01) (Hill et al., 2005)∗ Stress on PSS-10 items associated with worse sleep effectiveness on VSH at 1month post-discharge in path analysis (beta −0.281, p< 0.01) (Williams and Williams, 1997) Stress on PSS-10 item associated with worse sleep quality on 6-item GSDS (r = 0.36, p< 0.01) (Lee and Hsu, 2012) Stress for fathers on PSS:IH associated with shorter objective sleep quantity in 24hours (r=−0.62; p< 0.01) (Lee et al., 2007)∗ Qualitatively, parents reported opportunities for skin-to-skin/ involvement in infant care, overnight visiting policies helped manage stress and in turn improved sleep (Edéll-Gustafsson et al., 2015; Zamanzadeh et al., 2013a) Anxiety associated with worse sleep quality on PROMIS (r = 0.51; p< 0.01) (Busse et al., 2013) Qualitatively, parents reported anxiety, uncertainty and feeling of powerlessness affected sleep (Edéll-Gustafsson et al., 2015) Depression associated with worse sleep quality on PROMIS (r = 0.45; p< 0.05) (Busse et al., 2013) Depression on CES-D associated with worse sleep quality on PSQI (r = 0.496; p = 0.026) (Schaffer et al., 2013)

NS difference in sleep quality on PSQI based on stress on PSS-10 items (Schaffer et al., 2013) NS difference in maternal objective sleep quantity based on stress on PSS-10 item (Lee and Hsu, 2012) NS difference in maternal objective sleep quantity based on stress on PSS:IH (Lee et al., 2007)∗

NS difference in sleep quality on PSQI based on anxiety on STAI-state subscale (Schaffer et al., 2013)

NS difference in sleep quality on 6-item GSDS based on depression on EPDS (Lee and Hsu, 2012) NS difference in objectively sleep quantity or proxies of sleep quality based on depression on EPDS (Lee and Hsu, 2012)

CES-D, Center for Epidemiological Studies-Depression Scale; EPDS, Edinburgh Postnatal Depression Scale; GSDS, General sleep disturbance scale; ISI, Insomnia Severity Index; LOS, length of stay; M, mean; NS, Not significant; PROMIS; Patient Reported Outcomes Measurement Information System;. PSQI; Pittsburgh Sleep Quality Index; PSS: NICU: Perceived Stress Scale: Neonatal Intensive Care Unit; PSS:IH, Parental Stressor Scale: Infant Hospitalization’ PSS:VAS, Perceived Stress Scale: Visual Analogue Scale; SD, standard deviation; SEM, standard error of mean; TST, Total Sleep Time; WASO, Wake After Sleep Onset; RCSQ, Richards-Campbell Sleep Questionnaire; VSH, Verran and Snyder-Halpern Sleep Scale. ∗ mixed/pooled preterm and term samples. † Lee and Lee (2007) (n = 21) and Lee et al. (2007) (n = 55) include participants from same sample. Only unique factors investigated in the Lee and Lee (2007) are reported. †† Lee and Hsu (2012) (n-=55) and Lee et al. (2012) (n = 51) include participants from the same sample. Only unique factors investigated in the Lee et al. (2012) paper are reportedNote: Objective sleep results are italicized.

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Psychological variables Stress

Association

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cal and methodological heterogeneity precluded conduct of metaanalyses and further opportunities for high quality studies are identified. The finding that parent sleep quantity and quality is negatively impacted during their infant’s hospitalization is consistent with the literature on parents of older children on oncology and general hospital wards (Franck et al., 2013; McCann, 2008; McLoone et al., 2013; Meltzer et al., 2012), and parents of critically-ill children hospitalized in a pediatric intensive care unit (Stremler et al., 2014). Given literature reporting high rates of stress among parents of preterm infants (Jubinville et al., 2012; Misund et al., 2013), and possible linkage between stress and sleep in the general adult ˚ population (Akerstedt et al., 2007), insomniacs (Morin et al., 2003), and parents of hospitalized children (McCann, 2008; Meltzer et al., 2012), the associations between stress and sleep identified in this review are unsurprising. More specifically, stress about the child’s illness has been identified as interfering with sleep among parents of hospitalized children in the PICU (Stremler et al., 2011) and parents of children living with chronic illnesses (Meltzer and Moore, 2008). In contrast to examinations of parent sleep for other hospitalized pediatric populations, our review did not find any hospital-related or infant variables to be associated with sleep for parents of preterm infants. Most of the studies in our review focused exclusively on mothers, but a number of studies included fathers, of which two examined gender-based differences in sleep outcomes (Blomqvist et al., 2017; Lee et al., 2007). No differences in sleep quantity were reported. Stress was associated with shorter sleep quantity for Chinese-American fathers (Lee et al., 2007), but not for mothers during infant hospitalization (Lee et al., 2007; Lee and Hsu, 2012). However, mothers had worse sleep quality (objectively measured and self-reported) compared to partners in this same study (Lee et al., 2007). Little is known about sleep for fathers in general. Nonetheless, review results are partially in-line with existing literature suggesting that relative to fathers, mothers have worse sleep quality (more fragmented), despite sleeping for longer durations in the postpartum (Gay et al., 2004) and during PICU admissions (Stremler et al., 2014). Mechanisms explaining postpartum sleep disruption are multifactorial. Hormonal fluctuations and physical discomforts postdelivery are potential physiological explanations for altered postpartum sleep among new mothers (Parry et al., 2006). Infant feeding and care demands are commonly cited sources of postpartum sleep fragmentation for parents of full-term infants (Hunter et al., 2009). The last two decades have seen implementation of familycentered care practices and improvements in neonatal follow-up, such that previous parent outcomes may not be generalizable or necessary relevant to families today. Despite updated recommendations from the American Academy of Pediatrics (AAP) regarding safe infant sleep (Moon, 2016), research indicates that U.S bedsharing is on the rise (Colson et al., 2013), and has negative implications for sleep among mothers of full-term infants (Stremler et al., 2013; Volkovich et al., 2015). It is important to note that the majority of included studies in this review reported on parent sleep at home while their infant was hospitalized, such that direct infant care was not a contributor to parent sleep outcomes. Rather increased stress and bedtime worries, two factors proposed to impact sleep quantity and quality ˚ (Akerstedt et al., 2012, 2007), are more likely mechanisms explaining sleep disruption. Other potential reasons for poor parent sleep quality while at home during infant hospitalization, include waking to pump breastmilk or calling the hospital for an update, but such distinctions have not been reported in the included studies. While several studies examined various factors associated with altered sleep quantity and quality, none were sufficiently powered to comprehensively evaluate numerous possible predictors. Identi-

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fication of predictors is important to development of effective intervention programs. Strengths and limitations Strengths of our review include a comprehensive search strategy and attempt to obtain information on both sleep quality and quantity. The decision to include studies of different designs was a strength that enabled a comprehensive review of published research on this topic required to identify gaps and guide recommendations. However, there are a few limitations. First, we restricted to studies published in English language only, resulting in possible language bias. Second, because of heterogeneity in reporting of outcomes we were unable to conduct a meta-analysis. Third, studies conducted to date have been mainly cross-sectional and descriptive with small sample sizes. Thus, it is difficult to make generalized comments related to sleep outcomes from such studies. Only a few studies employed longitudinal and experimental designs or controlled for confounders; making it difficult to infer causal associations and differentiate predictors and outcomes of poor sleep. Clinical implications With knowledge of the impact of preterm birth on parent sleep, several interventions have been attempted and these included a guided imagery (Schaffer et al., 2013) and progressive muscle relaxation (Karbandi et al., 2015), as well as a bright-light therapy aimed at targeting misaligned sleep-wake cycles (Lee and Hsu, 2012). However, review of these interventions was beyond the scope of this review. The findings of our review highlight the importance for health professionals (e.g. nurses, midwives) to ask parents about their sleep patterns when visiting their neonate in order to identify families who may require extra support. Given associations between heightened stress and fathers’ and mothers’ sleep, strategies aimed at reducing stress may help maximize sleep for parents. Research limitations and implications We identified several potential future research implications from this review. As a result of the low number of studies with a parent of term infant control group, there is inconclusive evidence to inform if sleep for parents of preterm and term infants differs in the first postpartum year. Future research should include parents of full-term infants in the control group to provide a formal comparison to preterm family data. Designing studies that assess both reported and objectively measured infant and parent sleep, as well as adjusting for possible covariates (e.g. depression, social support), would further inform understanding of infant contribution to parent sleep. Sleep accommodation and hospital environment factors (e.g. suitable sleep accommodation, light, and noise) were relatively unexplored among included studies, despite being identified as important variables interfering with sleep attainment among parents of older children (Franck et al., 2013; Stremler et al., 2011). While the inclusion of fathers in more recent published literature highlights a growing awareness of the importance of including both parents when assessing the effects of preterm birth on health and family outcomes, small sample sizes limited power to detect gender-based differences. Socio-economic status, age, gender, marital status may have complex and potentially interactive associations with sleep behaviours and outcomes and should be explored using larger samples of mother-father dyads. Investigation of the effect of infant sleep location on sleep, health and safety outcomes for families of preterm infants following discharge is timely and

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necessary. Such information will help inform clinical recommendations and aid clinicians in identifying parents at risk for sleep disruption. Prospective longitudinal designs that include evaluation of sleep across multiple time points as well as the use of more advanced statistical approaches (e.g. multiple variable modeling) are warranted. Conclusion This systematic review of moderate quality evidence suggests that sleep is disrupted for parents of preterm neonates during hospitalization. Parents sleep for <7 h during infant hospitalization and the first month postpartum, their sleep quality is poor, and parent stress is the most consistent factor associated with sleep. This review highlights the lack of well-controlled studies assessing sleep in parents of preterm infants. There is currently insufficient evidence for reliable identification of correlates of reduced sleep quantity and poor sleep quality in parents of preterm infants. Given the potential consequences of sleep deprivation and the importance of physical and mental health of new parents, it is important to advance our understanding of sleep in parents of preterm infants in relation to contributing factors, health outcomes and effective interventions. Conflict of interest None declared. Ethical approval Not applicable. Funding source No external funding was received for this study. Acknowledgements Summer Haddad holds a doctoral trainee award from the Canadian Child Health Clinician Scientist Program (CCHCSP) and is supported by funding received from the Clinician-Scientist Training Program, SickKids-University of Toronto, Lawrence S. Bloomberg Faculty of Nursing, University of Toronto, Better Nights Better Days CIHR Team Grant in Pediatric Sleep. Dr. Stremler was recipient of an Early Researcher Award from the Ontario Ministry of Research and Innovation and currently holds the Lawrence S. Bloomberg Limited-Term Professorship in Child and Family Health. Dr. Shah holds an Applied Research Chair in Reproductive and Child Health Services and Policy Research awarded by the Canadian Institutes of Health Research (APR-126340). The funding agency had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication. The authors would like to acknowledge the help of Alanna Marson, librarian at the Hospital for Sick Children, Toronto, for her aid in the database search. Supplementary materials Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.midw.2019.01.009.

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