Background: Aboriginal children have a higher prevalence of overweight and obesity, with the influence of socioeconomic status being unclear. Our aim was to determine the changes in BMI between Australian Aboriginal and non-Aboriginal children as they move through adolescence into young adulthood.
Methods: A prospective cohort study of Aboriginal and non-Aboriginal children commenced in 2002 across 15 different screening centres involving 38 primary schools and 213 high schools across urban, regional and remote NSW. Based on postcode, socio-economic status was measured using the index of relative social advantage and disadvantage , and recorded at study enrolment. Participants’ BMI was measured every 2 years. We fitted a series of mixed linear regression models adjusting for age, Aboriginality, birth weight and socioeconomic status for boys and girls.
Results: 3418 (1949 Aboriginal) participants were screened over a total of 11, 387 participant years follow up. The prevalence of obesity was 14.2% (mean age 11 years) at baseline, and increased to 17.2% at eight years follow up (mean age 16 years). The mean BMI of Aboriginal girls was significantly higher than non-Aboriginal girls with increasing age (P<0.01). Girls born at low birth weight were of lower BMI than girls with a normal birth weight (P<0.001). Socioeconomic status and low birth weight had a differential effect on mean BMI for Aboriginal children compared to non-Aboriginal children (P for interaction = 0.01). Aboriginal boys of highest socioeconomic status had a higher BMI compared to non-Aboriginal boys, but not those of lower socioeconomic status. Non-Aboriginal boys of low birth weight were heavier than Aboriginal boys of low birth weight. Comment on Aboriginal and non-Aboriginal girls?
Conclusions: Socioeconomic status and birth weight has a differential effect on adiposity for Aboriginal boys, similar to that seen in low and middle income countries. Intervention programs need to recognise the differential risk for obesity for Aboriginal and non-Aboriginal boys and girls to maximise their impact.