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The effects of school starting age and relative age effects (RAEs) have generated much interest from parents, teachers, policymakers, and educational researchers. Our 10-year longitudinal study is based on a nationally representative (N = 4,983) prospective sample from the Longitudinal Study of Australian Children. The primary outcomes are results from the high-stake, Australia-wide National Assessment Program-Literacy and Numeracy tests in Years 3, 5, 7, and 9, controlling for demographic characteristics (gender, socioeconomic status, school type, and childhood cognition measured before the start of kindergarten). We evaluated how direct and mediated RAEs vary over the first 10 years of schooling for these longitudinal data. Results revealed significant RAEs in primary school years for both numeracy and literacy test outcomes. Effects were large in primary school years but declined in secondary school years. Although the direct effects of RAEs declined over time, there continued to be significant indirect effects over the whole 10-year period. RAEs in primary school had enduring effects that were mediated through the effects of earlier achievement. We juxtapose our results with previous RAE research on achievement and a range of other noncognitive outcomes where the RAEs are enduring into adolescence and even adulthood. We position our research within this broader research literature and discuss implications for educational policy, practice, theory, and future research.

Aim: Child health varies with body mass index (BMI), but it is unknown by what age or how much this attracts additional population health-care costs. We aimed to determine the (1) cross-sectional relationships between BMI and costs across the first decade of life and (2) in longitudinal analyses, whether costs increase with duration of underweight or obesity.Methods: Participants: Baby (n = 4230) and Kindergarten (n = 4543) cohorts in the nationally representative Longitudinal Study of Australian Children.Outcome: Medicare Benefits Scheme (including all general practitioner plus a large proportion of paediatrician visits) plus prescription medication costs to federal government from birth to sixth (Baby cohort) and fourth to tenth (Kindergarten cohort) birthdays.Predictor: biennial BMI measurements over the same period.Results: Among Australian children under 10 years of age, 5-6% were underweight, 11-18% overweight and 5-6% obese. Excess costs with low and high BMI became evident from age 4-5 years, with normal weight accruing the least, obesity the most, and underweight and overweight intermediate costs. Relative to overall between-child variation, these excess costs per child were very modest, with a maximum of $94 per year at age 4-5 years. Nonetheless, this projects to a substantial cost to government of approximately $13 million per annum for all Australian children aged less than 10 years.Conclusions: Substantial excess population costs provide further economic justification for promoting healthy body weight. However, obese children's low individual excess health-care costs mean that effective treatments are likely to increase short-term costs to the public health purse during childhood. [ABSTRACT FROM AUTHOR]

Background: Socioeconomic inequalities in longitudinal patterning of childhood overweight could cause marked differentials in total burden by adulthood. This study aims to determine timing and strength of the association between socioeconomic status (SES) and children’s body mass index (BMI) in the pre- and primary school years, and to examine socioeconomic differences in overweight trajectories across childhood. Methods: Participants were 4949 children from the Longitudinal Study of Australian Children. BMI was measured at four biennial waves starting at age 4–5 years in 2004. Developmental trajectories of childhood overweight were identified with latent class analyses. Composite variables of family and neighbourhood SES were used. Results: Socioeconomic differences in mean BMI z-scores already present at age 4–5 more than doubled by age 10–11 years, reflecting decreasing mean BMI among advantaged rather than increasing means among disadvantaged children. Latent class analysis identified children with ‘stable normal weight’ (68%), and with ‘persistent’ (15%), ‘late-onset’ (14%), and ‘resolving’ overweight (3%). Risks of persistent and late-onset childhood overweight were highest among low SES families (e.g. most disadvantaged quintile: ORpersistent = 2.51, 95%CI: 1.83–3.43), and only partly explained by birth weight and parental overweight. Relationships with neighbourhood SES were weaker and attenuated fully on adjustment for family SES. No socioeconomic gradient was observed for resolving overweight. Conclusions: Childhood has become the critical period when socioeconomic inequalities in overweight emerge and strengthen. Although targeting disadvantaged children with early overweight must be a top priority, the presence of childhood overweight even among less-disadvantaged families suggests only whole-society approaches will eliminate overweight-associated morbidity. [ABSTRACT FROM AUTHOR]

BACKGROUND AND OBJECTIVES: Parents often do not accurately perceive overweight and/or obesity in their children. Changing this is widely considered an essential first step to reducing child overweight, but recent research suggests that, in fact, this could promote greater weight gain. We aimed to determine the directionality over time between higher child adiposity and parental perception of child overweight. METHODS: Participants were from 2 cohorts of the population-based Longitudinal Study of Australian Children followed biennially since 2004. Repeated measures of BMI z scores and parental perceptions of overweight were available for the kindergarten cohort at 6 waves (ages 4-5, 6 -7, 8-9, 10-11, 12-13, and 14-15 years; n = 4632) and for the birth cohort at 4 waves (ages 2-3, 4-5, 8-9, and 10-11 years; n = 4445). Bidirectionality between overweight perception and BMI z score was examined by using cross-lagged regression models. RESULTS: In both cohorts, wave-on-wave lagged effects were strong (all: P < .001) but much larger from BMI z score to parent perception. For every unit increase in the BMI z score, the odds of a child being perceived as overweight in the next wave ranged from 2.9 (birth cohort: age 2-3 years) to 10.4 (kindergarten cohort: age 6-7 years). These effects were ~3 to 12 times larger than the reverse, whereby the perception of overweight predicted 0.2 to 0.5 higher BMI z score in the next wave. CONCLUSIONS: Higher child BMI z scores strikingly predicted a subsequent parental perception of child overweight. Parent-perceived overweight preceded rising (not falling) BMI, but these effects were small. Clinician efforts to make parents aware of overweight may not be harmful but seem unlikely to improve children's BMI status. [ABSTRACT FROM AUTHOR]

Objectives: Snacks contribute to overconsumption of energy-dense foods and thence obesity. Previous studies in this area are limited by self-reported data and small samples. In a large population-based cohort of parent-child dyads, we investigated how modification of pre-packaged snack food, i.e. (a) item quantity and variety, and (b) dishware (boxed container) size affected intake., Methods: Design: Randomized trial nested within the cross-sectional Child Health CheckPoint of the Longitudinal Study of Australian Children, clustered by day of visit., Sample: 1299 11-12 year olds, 1274 parents., Exposure: 2 × 2 manipulation of snack box container size and item quantity/variety: (1) small box, few items, (2) large box, few items, (3) small box, more items, (4) large box, more items., Procedure: Participants received a snack box during a 15 min break within their 3.5 h visit; any snacks remaining were weighed., Outcomes: Consumed quantity (grams) and energy intake (kilojoules)., Analyses: Unadjusted linear regression., Results: Children who were offered a greater quantity and variety of snack items consumed considerably more energy and a slightly higher food mass (main effect for energy intake: 349 kJ, 95% CI 282-416, standardized mean difference (effect size) 0.66; main effect for mass: 10 g, 95% CI 3-17, effect size 0.17). In contrast, manipulating box size had little effect on child consumption, and neither box size nor quantity/variety of items consistently affected adults' consumption., Conclusion: In children, reducing the number and variety of snack food items available may be a more fruitful intervention than focusing on container or dishware size. Effects observed among adults were small, although we could not exclude social desirability bias in adults aware of observation.

Background: Short sleep duration in childhood has often been linked with obesity in later childhood or adolescence. However, whether infant sleep duration affects body composition trajectories and cardiovascular health through to mid-adolescence remains unknown. Methods: Participants were 336 adolescents from a community-based prospective birth cohort in Melbourne, Australia. Mothers completed 24-hour time diaries, including infant sleep in 5-minute intervals at ages 2, 4, and 12 months. BMI and body composition outcomes were measured 6-monthly between 4 and 6.5 years and at 10 and 14 years. Cardiovascular outcomes at 14 years comprised blood pressure, pulse wave velocity, retinal arteriole-to-venule ratio, and carotid intima-media thickness. We used multivariable linear regression and multinomial logistic regression analyses adjusted for sex, age, BMI at birth, gestational age, ethnicity, maternal education, maternal BMI, and neighborhood socioeconomic position. Results: At 2 months, infants slept on average 14.1 hours [standard deviation (SD) 1.9], decreasing to 13.4 hours (SD 2.0) by 12 months. We observed no associations between the different sleep duration time points in infancy and later BMI or body composition. Moreover, a shorter sleep duration did not increase the odds of being on a high body composition trajectory compared with longer sleep ( e.g ., odds ratio per hour of sleep at 4 months is 0.85, 95% confidence interval 0.65-1.11). Infant sleep duration was also not associated with cardiovascular function or large or small artery structure at 14 years of age. Conclusions: We found no evidence that sleep duration very early in life affects adolescent body composition or cardiovascular health.

Background: Research suggests that general parenting dimensions and styles are associated with children's BMI, but directionality in this relationship remains unknown. Moreover, there has been little attention to the influences of both mothers' and fathers' parenting. We aimed to examine reciprocal relationships between maternal and paternal parenting consistency and child BMI., Methods: Participants were 4002 children and their parents in the population-based Longitudinal Study of Australian Children. Mothers and fathers self-reported parenting consistency, and children's BMI was measured at 4 biennial waves starting at age 4 to 5 years in 2004. Bidirectionality between parenting and child BMI was examined by using regression analyses in cross-lagged models., Results: The best-fitting models indicated a modest influence from parenting to child BMI, whereas no support was found for bidirectional influences. For mothers, higher levels of parenting consistency predicted lower BMI in children from Waves 1 to 2 and 3 to 4; for example, for every SD increase in mothers' parenting consistency at Wave 1, child BMIz fell by 0.025 in Wave 2 (95% confidence interval: -0.05 to -0.003). For fathers, higher levels of parenting consistency were associated with lower child BMI from Waves 1 to 2 and 2 to 3., Conclusions: Parenting inconsistency of mothers and fathers prospectively predicted small increases in offspring BMI over 2-year periods across middle childhood. However, child BMI did not appear to influence parenting behavior. These findings support recent calls for expanding childhood overweight interventions to address the broad parenting context while involving both mothers and fathers.

Objective: To investigate timing and strength of associations between mental health and overweight in childhood; to investigate how the cumulative burden of each of these problems affects the other., Methods: Participants were 3197 children in the population-based Longitudinal Study of Australian Children. At 4 biennial waves spanning ages 4-5 to 10-11 years, parents and teachers reported child mental health on the Strengths and Difficulties Questionnaire, and researchers measured body mass index (BMI). Outcomes were analyzed both continuously and dichotomized (clinical vs no mental health problems; overweight vs not overweight)., Results: Approximately 30% of participants had overweight and/or mental health problems at some point between ages 4-5 and 10-11 years. Small positive cross-sectional mental health-BMI associations emerged at 8-9 years and strengthened by 10-11 years. In longitudinal analyses, more episodes of overweight predicted higher Total Difficulties scores by 10-11 years, mainly reflecting greater Peer Problems and, to a lesser degree, Emotional Symptoms than never-overweight children; though modest, these associations were robust to a range of sensitivity analyses. In post hoc analyses, overweight in late childhood was more strongly associated with poorer mental health at 10-11 years than early and fluctuating childhood overweight. Associations were smaller and less robust for mental health problems prospectively predicting higher BMI., Conclusions: Relationships between poorer mental health and higher BMI emerged then strengthened in middle to late childhood. In childhood, it appears that overweight precedes mental health problems, particularly peer problems and-on a lower level-emotional problems, rather than the reverse., (Published by Elsevier Inc.)