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

Abstract

Background: Data on body mass index (BMI) in infants and toddlers worldwide are lacking, relative to older age groups.Objectives: To describe the growth (weight, length/height, head circumference, and BMI z-score) of New Zealand children under the age of 3 years, and examine differences by sociodemographic characteristics (sex, ethnicity, and deprivation). Methods: Electronic health data were collected by Wh anau Awhina Plunket, who provide free 'Well Child' services for approximately 85% of newborn babies in New Zealand. Data from children under the age of 3, who had their weight and length/height measured between 2017 and 2019, were included. The prevalence of BMI (WHO child growth standards) ≤2nd, ≥85th, and ≥95th percentiles were determined. Results: Between 12 weeks and 27 months of age, the percentage of infants ≥85th BMI percentile increased from 10.8% (95% CI, 10.4%-11.2%) to 35.0% (34.2%-35.9%). The percentage of infants with high BMI (≥95th percentile) also increased, particularly between 6 months (6.4%; 95% CI, 6.0%-6.7%) and 27 months (16.4%; 15.8%-17.1%). By contrast, the percentage of infants with low BMI (≤2nd percentile) appeared steady between 6 weeks and 6 months, and declined at older ages. The prevalence of infants with a high BMI appears to increase substantially from 6 months across sociodemographic characteristics, with a widening prevalence gap by ethnicity occurring from 6 months, mirroring that of infants with a low BMI. Conclusions: The number of children with high BMI increases rapidly between 6 months and 27 months of age, suggesting this is an important timeframe for monitoring and preventive action. Future work should investigate the longitudinal growth trajectories of these children to determine if any particular patterns predict later obesity and what strategies could effectively change them.

Adherence to Infant Feeding Guidelines in the First Foods New Zealand Study

“…Variables were reported as percentages and means (standard deviation (SD)) from the study population. The proportions of the sample that met the indicator were also adjusted by weighting for ethnicity and socioeconomic deprivation to represent the New Zealand population more closely [38] and estimate adherence with a 95% logit-transformed confidence interval. Logistic regression was used to estimate odds ratios, 95% confidence intervals, and p-values for associations between sociodemographic characteristics and adherence to different indicators, and p-values < 0.05 indicated statistical significance.…”

“…Adherence to the MoH infant feeding guidelines (Table 1) is shown in Table 4, with further detail regarding each indicator and sociodemographic predictors provided below. The proportions of the sample that met the indicator were also weighted for ethnicity and socioeconomic deprivation in Table 4 to more closely represent the New Zealand population [38], allowing wider conclusions to be made.…”

Baby Food Pouches, Baby-Led Weaning, and Iron Status in New Zealand Infants: An Observational Study

“…The proportion of infants in each of the iron status categories was reported for the study sample and weighted by ethnicity and household socioeconomic deprivation to better reflect the New Zealand population [36], generating weighted estimates and 95% CIs for the prevalence.…”

“…Approximately half (49%) were primiparous. Infants with high socioeconomic deprivation were somewhat under-represented, comprising 24% of those participants with iron status data compared to 28% in a national dataset of New Zealand households with infants [36]. Nearly all infants (98%) had been breastfed at some point, and 68% were breastfed at the time they took part in the study (mean age 8.3 months).…”

“…a Estimates are weighted for ethnicity and socioeconomic deprivation level to more closely represent the New Zealand population[36]. b BRINDA (Biomarkers Reflecting Inflammation and Nutritional Determinants of Anaemia) method used to adjust for inflammation[30,31].…”