Elsevier

Sleep Medicine

Volume 14, Issue 3, March 2013, Pages 266-273
Sleep Medicine

A longitudinal study of child sleep in high and low risk families: Relationship to early maternal settling strategies and child psychological functioning

https://doi.org/10.1016/j.sleep.2012.11.006Get rights and content

Abstract

Objectives

To investigate whether sleep disturbances previously found to characterise high risk infants: (a) persist into childhood; (b) are influenced by early maternal settling strategies and (c) predict cognitive and emotional/behavioural functioning.

Methods

Mothers experiencing high and low levels of psychosocial adversity (risk) were recruited antenatally and longitudinally assessed with their children. Mothers completed measures of settling strategies and infant sleep postnatally, and at 12 and 18 months, infant age. At five years, child sleep characteristics were measured via an actigraphy and maternal report; IQ and child adjustment were also assessed.

Results

Sleep disturbances observed in high-risk infants persisted at five years. Maternal involvement in infant settling was greater in high risk mothers, and predicted less optimal sleep at five years. Poorer five year sleep was associated with concurrent child anxiety/depression and aggression, but there was limited evidence for an influence of early sleep problems. Associations between infant/child sleep characteristics and IQ were also limited.

Conclusions

Early maternal over-involvement in infant settling is associated with less optimal sleep in children, which in turn, is related to child adjustment. The findings highlight the importance of supporting parents in the early development of good settling practices, particularly in high-risk populations.

Introduction

Previous research has identified associations between family stress or low SES and poor sleep quality in children [1], [2], [3], [4]. Collectively, the samples studied have spanned infancy to late childhood, and effect sizes have been small to medium in magnitude. Thus, in a prior report, we examined the development of infant sleep from birth through to 18 months in a longitudinal study of women who were or were not experiencing high levels of psychosocial adversity during pregnancy [1]. Infant sleep characteristics were comparable across high and low adversity groups in the first three months of life. However, by 18 months of age, high risk group infants showed more sleep problems (i.e., settling and/or night waking problems, variability in bedtimes and sleep durations) as indexed by both maternal questionnaire and sleep diary. Moreover, psychosocial adversity in our sample was also associated with less optimal maternal settling strategies in early development, which predicted poorer infant sleep at 18 months [1].

The importance of childhood sleep problems is highlighted by existing work, which has found that such difficulties are associated with poorer cognitive and behavioural/emotional outcomes [5]. In the cognitive domain, both experimental manipulations of child sleep and observations of naturalistic sleep characteristics have suggested that sleep is an important influence on cognitive functioning. In studies of school aged children, relatively modest experimental reductions (as little as one hour) in the amount of sleep have been found to have a detrimental impact on performance on tasks requiring sustained attention, behavioural inhibition, and memory [6], [7], [8], [9]. Observational studies have similarly identified a relationship between day-to-day sleep quality and child cognitive functioning [4], [5], [9]. Notably, there is also some evidence for associations between sleep disturbance and poorer cognitive functioning in the longer term. Thus, reduced academic performance has been observed in the presence of sleep-related breathing disorders [10], as well as, in the context of poor sleep duration and/or quality in studies of normative samples [5], [8]. In addition, a small number of studies have documented concurrent associations between child sleep and trait like cognitive capacities (IQ), although findings have been inconsistent. Specifically, while positive associations between sleep duration and IQ dimensions have been documented in some cases [11], [12], others have found longer sleep durations to be associated with lower IQ test scores [13]. The mean age of children in these cross-sectional studies ranged from six to nine years. In addition, a longitudinal study has demonstrated that shorter sleep durations in children aged eight years predicted lower intellectual ability scores at 10 years (small to medium effect sizes), even taking account of eight year cognitive ability scores [14].

With regard to emotional and behavioural adjustment, sleep difficulties have been associated with the presence of affective (e.g., anxious/depressed) and externalising symptoms in children and adolescents [2], [5], [15], [16], [17], [18], [19], [20]. Although sleep problems may in part be symptomatic of underlying disorder [21], there is also evidence to suggest that sleep disturbances themselves contribute to adjustment problems. Medical and behavioural interventions that tackle sleeping difficulties are associated with broader functional improvements [22], [23], [24], [25]. Moreover, longitudinal cohort studies have highlighted prospective associations between childhood sleep difficulties and later emotional problems (anxiety and/or depression) and externalising difficulties (attentional problems and aggression) [18], [26], [27], [28], [29], [30]. These longitudinal effects occur over and above any existing adjustment problems; samples have included children as young as four years and have predicted adjustment as late as adulthood. Nevertheless, some limitations of previous studies have been highlighted, including the use of extremely brief assessments of child sleep quality and/or reliance on a single informant (mothers) to index both sleep and adjustment problems [31], [32]. There have also been some notable null findings [28], [33]. In particular, in a study incorporating comprehensive assessments of child sleep quality, little evidence was found for longitudinal associations with externalising difficulties [34].

A striking feature of research to date is that few studies of younger children and infants have been conducted. A preliminary, small scale study of infants with severe and chronic sleep problems aged six to 12 months found significantly higher rates of ADHD at five years relative to a non-sleep disordered comparison group (7/25 versus 0/25) [19]. In addition, one cohort study included brief maternal reports of sleep problems in infancy (six months) and found limited evidence for an association with attention problems at five and 14 years. Although a stronger pattern of results was obtained for two to four year sleep problems, these were measured retrospectively by maternal report at five years [35]. A third longitudinal study measured maternal perceptions of infant sleep problems (present/absent on a single item) at four, 12 and 24 months infant age, and found no prospective associations with child emotional and behavioural adjustment at six years [36]. Thus, associations between sleep quality and later adjustment have not consistently been demonstrated when sleep has been studied in infancy and toddlerhood.

The origins of child sleep problems have also been examined. Parental settling strategies have been highlighted as one potentially important influence on sleep development, with more active parental settling behaviours being hypothesised to reduce opportunity for the infant to learn to self-settle [37], [38]. Consistent with this view, parental presence or active involvement in settling the child to sleep has been found to be a correlate of poorer sleep quality in the first three years of life [37], [38], [39], [40]. However, cross-sectional observations are difficult to interpret, since infant sleep difficulties may elicit maternal involvement and vice versa [38]. Longitudinal data on this point are extremely limited. In our previous report based on the current sample we found that elevated levels of ‘parental presence’ settling strategies at 12 weeks predicted poor infant sleep at 18 months of age [1] (medium to large effect sizes). Two other longitudinal studies focused on the first two years of life, have reported similar associations [41], [42]. However, longer term outcomes associated with early parental settling involvement have not been studied.

In summary, the extant literature highlights associations between sleep problems and adverse cognitive and behavioural–emotional outcomes in children, although studies have mainly relied on parental reports of sleep problems and have focused on school aged children and adolescents. Previous work also links higher levels of parental involvement during the period of settling to sleep with the emergence of sleep problems, but there is limited longitudinal data on this point and studies have focused on the first two years of life. We addressed these issues through an extension of our existing longitudinal study [1], in which we identified early disturbances in sleep characteristics in children growing up in environments characterised by high levels of psychosocial adversity. In the current study, we followed up the same longitudinal sample at the age of five years for the child and examined whether: (a) risk-related disturbances in sleep characteristics that were previously observed at 12 and 18 months of age were also apparent in childhood; (b) maternal overinvolved settling strategies early in development predicted persistent sleep disturbances; and (c) disturbances in child sleep were prospectively and/or concurrently related to child functioning in cognitive, behavioural and emotional domains. With respect to the latter, we were particularly interested in whether observations of associations between sleep disturbances and anxiety/depression, aggression and lower IQ described in the extant literature would be replicated in a younger age group. Given the potential confound that arises between maternal reports of sleep problems and perceptions of child difficulties more generally, we assessed child sleep objectively, using actigraphy, as well as via a diary report and questionnaire.

Section snippets

Method

The study was reviewed by the University of Reading Research and Ethics Committee and the Berkshire NHS Research Ethics Committee (ref. 05/Q1602/124). All mothers provided informed consent after a full explanation of study procedures.

Preliminary analyses

Descriptive statistics for children in the sample are presented by group in Table 1. High and low risk groups showed similar gender distributions, but there was a trend for the high risk children to be slightly older than their low risk counterparts at five years (mean difference 1.4 months, p = .072), and the high risk group children had lower birth weights [high risk M = 3.30 Kg, SD = 0.57, low risk M = 3.51, SD = 0.50; t120 = 2.09, p < 0.05]. These potentially relevant variables were screened as covariates.

Discussion

The key findings from the current study were as follows. First, previously reported associations between psychosocial adversity and sleep quality in infants in the current sample were maintained in childhood. Second, even once risk group effects were taken into account, maternal settling strategies in the first months of life predicted sleep quality at five years. Third, consistent with previous research, there was some evidence of associations between child sleep quality and levels of

Conflict of Interest

The ICMJE Uniform Disclosure Form for Potential Conflicts of Interest associated with this article can be viewed by clicking on the following link: http://dx.doi.org/10.1016/j.sleep.2012.11.006.

. ICMJE Form for Disclosure of Potential Conflicts of Interest form.

Acknowledgements

This research was funded by a Nuffield New Career Development Fellowship (Sarah L. Halligan), the Foundation for Sudden Infant Death, and a NHS Executive South East Project Grant. We thank Melanie Mardon, Lindsay Cox, Claire Lawson, Elizabeth Bell, Sarah Healy and Sarah Sampson for their assistance with data collection; and families in our study for so generously giving us their time.

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