Further reductions in the prevalence of obesity in 4-year-old New Zealand children from 2017 to 2019

Abstract

Objective To 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. Methods As 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. Results The 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. Conclusions Reassuringly, 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.

Prevalence of low and high BMI during the first 3 years of life: using New Zealand national electronic health data

“…8 While we report an increase in the prevalence of high BMI from 6 months to 27 months of age, our data on 4-year-old children suggest that the prevalence, if anything, then decreases from 16.4% at 27 months (presented herein) to 12.5% at 4 years of age. 8 A key feature of our results is the 'widening of the gap' in prevalence by area-level deprivation and ethnicity. As is widely observed in young children, 10,[26][27][28] growth in New Zealand infants also varies dramatically by ethnicity as shown in Figure 1.…”

“…6,7 In contrast, we recently reported that the prevalence of obesity is declining in 4-year-old children in New Zealand across all ethnic groups and deprivation levels. 8 Our findings suggest that this subgroup of the New Zealand population is in the 'fourth stage' of the obesity transition, turning the corner towards a declining prevalence. 9 Whether such patterns are apparent in younger children in New Zealand is currently unknown, although international data are growing in the under 3 year age group.…”

“…19 For this analysis, the prevalence of BMI ≤2nd percentile and ≥85th and ≥95th percentiles were calculated to allow our data to be comparable to that of previously published data on 4-year-old children in New Zealand. 8 Low and high BMI are defined in this study as ≤2nd percentile and ≥95th percentile, respectively. WHO recommended cut-offs for BMI z-score (<À2 SD, >1 SD, >2 SD, and >3 SD) are also presented herein to allow for comparisons with other published data.…”

Changes in referral patterns for weight in association with the preschool Raising Healthy Kids target

“…Research suggests levels of childhood overweight and obesity declined slightly in NZ 4-year-old children between 2011 and 2019. 13 Despite this, approximately 6700 (12.5%) 4-year-old children were estimated to be affected by obesity in 2018-19. 13 In 2016, a new national health target known as the 'Raising Healthy Kids (RHK) target' was embedded within the B4SC programme by the NZ Government, stating that 'by December 2017, 95% of obese children identified in the B4SC programme will be offered a referral to a health professional for clinical assessment and family-based nutrition, activity and lifestyle interventions'.…”

“…13 Despite this, approximately 6700 (12.5%) 4-year-old children were estimated to be affected by obesity in 2018-19. 13 In 2016, a new national health target known as the 'Raising Healthy Kids (RHK) target' was embedded within the B4SC programme by the NZ Government, stating that 'by December 2017, 95% of obese children identified in the B4SC programme will be offered a referral to a health professional for clinical assessment and family-based nutrition, activity and lifestyle interventions'. 14, p. 3 The expectation was that any children identified with obesity at the B4SC would be referred on for further assessment and management 15 -a process mandated by reporting to the Ministry of Health (MoH) for the 'RHK health target'.…”