Abstract
ObjectiveTo examine whether the prevalence of age- and sex-adjusted BMI at, or above, the 85th, 95th and 99.7th percentiles continues to decline in New Zealand preschool children, over time.MethodsAs part of a national screening programme, 438,972 New Zealand 4-year-old children had their height and weight measured between 2011 and 2019. Age- and sex-adjusted BMI was calculated using WHO Growth Standards and the prevalence of children at, or above, the 85th, 95th, and 99.7th percentiles and at, or below, the 2nd percentile were determined. Log-binomial models were used to estimate linear time trends of ≥85th, ≥95th and ≥99.7th percentiles for the overall sample and separately by sex, deprivation, ethnicity and urban-rural classification.ResultsThe percentage of children at, or above, the 85th, 95th and 99.7th percentile reduced by 4.9% [95% CI: 4.1%, 5.7%], 3.5% [95% CI: 2.9%, 4.1%], and 0.9% [95% CI: 0.7%, 1.2%], respectively, between ‘2011/12’ and ‘2018/19’. There was evidence of a decreasing linear trend (risk reduction, per year) for the percentage of children ≥85th (risk ratio (RR): 0.980 [95% CI: 0.978, 0.982]), ≥95th (RR: 0.966 [95% CI: 0.962, 0.969]) and ≥99.7th (RR: 0.957 [95% CI: 0.950, 0.964]) percentiles. Downward trends were also evident across all socioeconomic indicators (sex, ethnicity, deprivation, and urban-rural classification), for each of the BMI thresholds. Larger absolute decreases were evident for children residing in the most deprived compared with the least deprived areas, at each BMI threshold. There appeared to be no consistent trend for the percentage of children ≤2nd percentile.ConclusionsReassuringly, continued declines of children with age- and sex-adjusted BMI at, or above, the 85th, 95th and 99.7th percentiles are occurring over time, overall and across all sociodemographic indicators, with little evidence for consistent trends in the prevalence of children at, or below, the 2nd percentile.
Highlights
Action on high Body Mass Index (BMI) in childhood is recognised as imperative
There are area level differences in child obesity rates in New Zealand, partially driven by differences in obesogenic environments [3,4,5]. These differences may represent inequities in access to the socioeconomic determinants of health, varying food and physical activity environments, as well as access to care and the quality of care received; all of which influence the risk of increased weight, and the effectiveness of interventions [2, 6]
There were larger absolute population subgroups investigated. We explored this further and decreases in each of the BMI percentiles for children residing in cannot attribute this to error in the data (i.e., outliers or a coding the most deprived (Q5) areas compared with those living in the error), or to a change in the weight, height or age distibution of least deprived (Q1) areas (≥85th percentile, Q5: 6.8% [95% CI: participants (Supplementary A)
Summary
Action on high Body Mass Index (BMI) in childhood is recognised as imperative. From ‘2011/12’ to ‘2018/19’, (ii) examine whether any differences in trends were consistent across sociodemographic characteristics (i.e., sex, ethnicity, deprivation and urban-rural classification), and (iii) determine the prevalence of children with a BMI z-score at, or below, the 2nd percentile.
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