The mediating role of sleep in the relationship between Indigenous status and body mass index in Australian school-aged children

Impact of sleep on educational outcome of Indigenous Australian children: A systematic review

INTRODUCTION

The association between quality sleep and improved cognition is well reported in literature. However, very few studies have been undertaken to evaluate the impact of poor sleep on educational outcomes in Indigenous Australian children.

OBJECTIVES

The objective of this review was to explore the association between sleep and educational outcomes of Indigenous children.

METHODS

For this systematic review, a literature search covering research articles in academic databases and grey literature sources was conducted to retrieve studies published until March 2022. Eight online e-databases (PubMed, Ovid MEDLINE, CINAHL, SCOPUS, HealthinfoNet, PsycINFO, Cochrane and Google Scholar) were searched for data extraction and two appraisal tools (NIH and CREATE) were used for quality assessment. Studies that explored any aspect of sleep health in relation to educational/academic outcomes in school going Indigenous Australian children aged 5-18 were included in this study. All review articles and studies that focused on physical/ mental disabilities or parent perceptions of sleep and educational outcomes were excluded. A convergent integrated approach was used to collate and synthesize information.

RESULTS

Only three studies (two cross-sectional and one longitudinal) met the eligibility criteria out of 574 articles. The sample size ranged from 21-50 of 6 to 13 year old children. A strong relationship was indicated between sleep quantity and educational outcomes, in two of the three studies. One study related the sleep fragmentation/shorter sleep schedules of short sleep class and early risers with poorer reading (B = -30.81 to -37.28, p = 0.006 to 0.023), grammar (B = -39.79 to -47.89, p = 0.012-0.013) and numeracy (B = -37.93 to -50.15, p = 0.003 to 0.022) skills compared with long sleep and normative sleep class whereas another reported no significant relation between sleep and educational outcomes.

CONCLUSION

The review highlights the need for more research to provide evidence of potentially modifiable factors such as sleep and the impact these may have on academic performance.

Association between indigenous status and Body Mass Index (BMI) in Australian adults: Does sleep duration affect the relationship?

Background

Overweight/obesity is a well-defined risk factor for a variety of chronic cardiovascular and metabolic diseases. Sleep duration has been associated with overweight/obesity and other cardio metabolic and neurocognitive problems. Notably, overweight/obesity and many of the associated comorbidities are prevalent in Indigenous Australians. Generally, sleep duration has been associated with BMI for Australian adults but information about Australian Indigenous adults’ sleep is scant. A recent report established that sleep is a weak predictor of obesity for Indigenous Australian adults.

Aim

To determine whether sleep remains a predictor of obesity when physical activity, diet and smoking status are accounted for; and to determine whether sleep duration plays a mediating role in the relationship between Indigenous status and BMI.

Methods

Statistical analyses of 5,886 Australian adults: 5236 non-Indigenous and 650 Indigenous people aged over 18 years who participated in the Australian Health Survey 2011–2013. Demographic and lifestyle characteristics were described by χ² and t-tests. ANOVA was used to determine the variables that significantly predicted BMI and sleep duration. Stepwise regression analyses were performed to determine the strongest significant predictors of BMI. Sleep duration was self-reported; BMI was calculated from measurement.

Results

The study revealed two main findings: (i) short sleep duration was an independent predictor of obesity (adjusted-R² = 0.056, p <0.0001); and (ii) controlling for sleep duration and other possible confounders, Indigenous status was a significant predictor of BMI overweight/obesity. Sleep duration played a weak, partial mediator role in this relationship. Increased BMI was associated with lower socioeconomic status and level of disadvantage of household locality for non-remote Indigenous and non-Indigenous people.

Conclusion

Indigenous status strongly predicted increased BMI. The effect was not mediated by the socioeconomic indicators but was partially mediated by sleep duration.

Sleep health in Indigenous Australian children: a systematic review

OBJECTIVE/BACKGROUND

The health and wellbeing of Indigenous Australian children has long been an issue of concern. However, to date there is a lack of attention to sleep health (particularly education and appropriate health service availability) in Indigenous Australians. The present review aimed to evaluate the prevalence of sleep problems in Indigenous Australians children.

METHOD

Up to August 2020, a systematic search using the keywords: "sleep problems"; "sleep disturbances"; "sleep quality"," "sleep disorder"; "sleep apnoea"; "obstructive sleep apnoea"; "OSA"; and "sleep-disordered breathing" AND "Indigenous Australians"; "Aboriginal"; "Torres Strait Islander"; was conducted on PubMed; Informit Indigenous Collection Scopus and CINAHL; "LIt.search tool" from the Lowitja Institute; Indigenous HealthInfoNet, Google Scholar (advanced), government agencies and relevant grey literature.

RESULTS

The search found only 13 studies focusing on sleep issues in Indigenous Australian children (birth to 17 years) with a pool of up to 4664 participants with 11 community-based studies (using mostly parental or self-report) and two in clinical populations (sleep laboratory). Three studies were longitudinal, all others were cross-sectional. Insomnia symptoms varied from 15% to 34.7%. Indigenous children reported severe daytime sleepiness (20%), short sleep (10.9%) late sleepers (50%). Snoring was reported in 14.2% with children in the community while up to 51% were objectively diagnosed to have OSA in a clinical setting.

CONCLUSION

The availability of only 13 studies investigating paediatric Indigenous sleep highlights the paucity of data in this area. Compared with non-indigenous people, Indigenous children are significantly more likely to experience short sleep duration and a high proportion reported symptoms of sleep disordered breathing. Working and conferring with Indigenous communities is an opportunity to engage in partnerships to improve sleep health and subsequently general health.

Late bedtime and body mass index gain in indigenous Australian children in the longitudinal study of indigenous children

AIM

To explore sleep patterns in indigenous Australian children and assess the role of sleep timing in longitudinal changes in body mass index (BMI).

METHODS

Latent profile analysis was conducted with the Australian Longitudinal Study of Indigenous Children (LSIC) cohort data (wave 5), to determine distinct patterns of bed and wake timing, taking account of weekday sleep duration, weekday and weekend bedtimes, and weekday wake times. Multilevel models with a random intercept were used to investigate the role of baseline sleep pattern in predicting longitudinal changes in BMI.

RESULTS

Baseline data for 1258 children (50.7% males), mean age 6.32 ± 1.52 years, indicated the presence of five classes of sleep patterns: early/long sleepers (4.5%), normative sleepers (25.5%), late sleepers (49.9%), consistent late sleepers (11.1%) and early risers (9%). Late sleeping was significantly associated with longitudinal gains in BMI. Compared with early sleepers, consistent late sleepers experienced 1.03 unit gain in BMI at follow-up (95% CI: 0.001-2.05, P = .05).

CONCLUSION

This study underscores the importance of looking beyond sleep duration and highlights the positive outcomes of early bedtimes in children. As sleep timing is modifiable, this offers the opportunity for improvement in sleep and protecting against future weight gain in indigenous children.

Is sleep duration associated with overweight/obesity in Indigenous Australian adults?

Background

Associations between high BMI and sleep duration and chronic illness are recognised. Short sleep is an accepted predictor of high BMI for children, including Indigenous Australian children. Short sleep has also been associated with high BMI in Australian adults, although not specifically in Indigenous Australian adults. This study aims to determine whether the relationship between sleep duration and BMI observed in non-Indigenous adults holds for Indigenous adults.

Methods

Data collected from 5204 non-Indigenous and 646 Indigenous participants aged over 18 years in a nationally representative Australian Health Survey 2011–2013 were analysed. Sleep duration was self-reported as the time between going to bed and time waking up; BMI was derived from measurement and categorised into normal weight (BMI = 18.5–24.9) and overweight/obese (BMI ≥ 25). Logistic regression was performed for the non-Indigenous and Indigenous groups separately to examine the association between sleep duration and BMI in each group.

Results

Proportionally more Indigenous people were classified as overweight/obese than non-Indigenous (χ² = 21.81, p < 0.001). Short sleep was reported by similar proportions in both groups (Indigenous 15% vs non-Indigenous 17%) whereas long sleep of > 9 h was reported by proportionally more Indigenous than non-Indigenous people (41% vs 26%). Without accounting for possible confounders, the association between sleep duration and BMI for the Indigenous group was not significant but a possible dose-response relationship was evident, with the odds of overweight/obesity being greatest for those who typically slept < 7 h (OR = 1.77, 95% CI 0.38–3.94) and < 6 h (OR = 1.55, 95%CI = 0.58–4.14). The same model for the non-Indigenous group was significant, with the odds of overweight/obesity being greatest for those who typically slept < 6 h (OR = 1.67, 95%CI 1.25–2.25). The risk of overweight/obesity diminished for both groups with sleep > 7 h. Accounting for a range of socioeconomic and personal confounders attenuated the strength of these relationships marginally.

Conclusion

Adding to reports relating sleep duration and BMI for Australian adults, this study provides evidence for an inverse relationship in non-Indigenous adults and suggests a similar trend for Indigenous adults. This trend was non-significant but is consistent with previous results for Indigenous children.