Bidirectional associations between sleep and dietary intake in 0–5 year old children: A systematic review with evidence mapping

Summary

We have undertaken a systematic review examining the role of diet on sleep, and sleep on diet, in children aged 0–5 y. Controlled trials and cohort or cross-sectional studies were identified with online searches of PubMed, Medline, Embase, Scopus, and CENTRAL up to 1 June 2019, and hand searching of relevant publications. Searches, extraction, and risk of bias assessments were undertaken independently by at least two researchers. Fifty articles involving 72,491 children on a diverse range of topics were eligible. All five studies that investigated the effect of sleep on diet indicated that poorer sleep (measured by a variety of indices) was associated with greater dietary energy intake or poorer diet quality. Conversely, the findings regarding how diet might influence sleep were less consistent when considering feeding practises, energy and macronutrient intake, or micronutrient and small metabolite intake. Studies were typically of short duration and relied on subjective measures of sleep (66%) or diet (88%). While we identified a clear relationship between reduced sleep and poorer diets, future studies require improved methodological reporting and support from transdisciplinary collaborations to better understand the possible role of diet on sleep. Prospectively registered with PROSPERO International Prospective Register of Systematic Reviews (CRD42018091647).

Introduction

While individual countries have reported a stabilisation of obesity rates in young children, the global prevalence of obesity in children under the age of five continues to rise [1]. Weight status tracks from childhood onwards [2], with overweight children likely to remain overweight as adults [1], facing an increased risk of non-communicable diseases over the life course [3]. It is well-established that prevention is key to improving childhood obesity rates, and that infancy to early childhood is a critical period for developing healthy eating and activity habits that persist into later life [1,3,4]. While diet and physical activity have long been cornerstones of obesity prevention strategies, difficulties in modifying these behaviours in the long-term suggest that investment in other approaches is warranted [5].

Such an approach might be via sleep, given that short sleep duration has been identified as a strong, independent risk factor for obesity in children, including infants [[5], [6], [7], [8], [9]]. Indeed, two recent trials have determined that sleep interventions during infancy can benefit weight long-term [10,11]. However, the mechanism(s) whereby insufficient sleep leads to increased weight gain are uncertain [5,[12], [13], [14]], although thought to be mediated primarily through an increase in dietary energy intake [12]. A recent systematic review and meta-analysis in children aged two to 18 y indicated that short sleep was associated with unhealthy dietary habits and positive energy balance [15]. These studies have shown that shorter sleep leads to a greater energy intake [16] or a preference for more calorie-dense and sweeter foods [16,17] in teenagers, with similar outcomes observed among preschool [18] and school aged children [19].

However, there are challenges with assessing relationships between sleep and diet, particularly in infants and toddlers as their dietary needs and sleep requirements change rapidly [20,21], and subjective methods of data collection introduce bias. While studies have investigated associations between sleep and macronutrient intake (fat, protein, and carbohydrate), sleep and micronutrient intake (vitamins and minerals), and sleep and small metabolites (such as amino acids and phenolic compounds) [22], the possible bi-directional nature of the relationship between sleep and diet (where it is equally feasible that sleep affects diet as diet affects sleep) has not been explored [23]. Perhaps this is why, despite the considerable health impacts of obesity on population risk factors for non-communicable disease and premature mortality, few systematic reviews of sleep and diet have been conducted for children aged five years or younger.

This review investigates the bidirectional associations between sleep and diet in children aged five years and younger. We define the eligible studies in this area with evidence mapping [24], identifying knowledge gaps with a visual presentation of research topics and study types as well as the methods used to measure sleep and dietary intake in the existing literature. We conclude by suggesting future directions in the study of sleep and diet in children.