BMI Trajectories Among Aboriginal Children In Canada

Transcription

1 BMI Trajectories Among Aboriginal Children In Canada Piotr Wilk The University of Western Ontario Martin Cooke University of Waterloo Michelle Sangster Bouck Middlesex-London Health Unit

2 Research Program To better understand the multiple, interrelated factors that affect various health outcomes of Aboriginal children, including obesity To identify culturally and contextually appropriate intervention frameworks, in partnership with community organizations and members To pilot these interventions in several contexts Supported by CIHR s Catalyst Grant

3 Current Study To examine differences in Body Mass Index (BMI) trajectories between offreserve Aboriginal children and non- Aboriginal children To assess differences between girls and boys To explore the relationship between BMI scores and rates of overweight and obesity

4 National Crises Obesity is one of the most significant negative health outcomes facing Aboriginal children About 20% of off-reserve Aboriginal children are classified as obese, compared to the national average of 7% (Canadian Community Health Survey, 2004)

5 Data Source National Longitudinal Survey of Children and Youth: Cycles 1 to 6 ( ) Four cohorts of children: 2- and 3-year-olds at Cycle 1 (1994/95) 2- and 3-year-olds at Cycle 2 (1996/97) Children were followed until they were 11 years of age (in ) Sample of 313 Aboriginal children and 6,054 non-aboriginal children

6 Measurement Instruments Body Mass Index (BMI): Weight in kilograms divided by the square of height in meters Based on parental reporting of child s weight and height Ethnic origin: Aboriginal (First Nations, Métis, Inuit) Non-Aboriginal Gender

7 Data Analysis Latent growth curve modeling techniques: Multi-cohort growth model (sequential cohort design) Statistical adjustments: Individually-varying times of observation Attrition/missing data points Sampling weights

8 BMI by Aboriginal Status

9 BMI by Aboriginal Status & Gender

10 BMI and Obesity Adults: BMI cut-offs to define obesity and overweight are based on fixed BMI values related to health risk (18.5, 25, 30) Children: no risk-based fixed BMI cut-off points: BMI varies considerably with age No agreement on risk related criteria BMI of a child is compared with the BMI of a reference population of children of the same age and sex

11 Reference Populations No Aboriginal or Canadian reference population to define cut-offs for childhood overweight and obesity Center for Disease Control and Prevention (CDC) growth charts: sex specific BMI-forage growth curves for ages 2 thought 19 International Obesity Task Force (IOTF) cut offs: a set of smoothed sex-specific BMI cut offs values that matched the adult cut offs of a BMI of 25 and 30 at age 18

12 Overweight - CDC

13 Overweight - IOTF

14 Obesity - CDC

15 Obesity - IOTF

16 Conclusions Aboriginal children have higher BMI scores and higher rates of overweight and obesity than non-aboriginal children throughout childhood Aboriginal boys between ages 6 and 11 have relatively high BMI scores and are more likely to be classified as overweight and obese IOTF tends to give lower estimates of obesity rates than CDC

17 Implications Aboriginal children represent increasing proportion of all children in Canada Aboriginal children, boys in particular, may experience high risk for obesity and many of the related negative health outcomes Childhood obesity might have devastating social and economic consequences for Aboriginal people unless preventative measures are taken

18 Limitations Self-reported weight and height: Parental reporting of child s weight and height Tend to overestimate child s BMI score Analysis of between-group differences is affected less by self-reporting No comparison across Aboriginal groups

19 Future Research Predictors of BMI trajectories: lifestyle, diet, socio-economic status, family characteristics, environmental factors Long term consequences of childhood obesity: high blood pressure, diabetes, self-esteem Identification of BMI standards for Aboriginal children Differences between on-reserve and offreserve Aboriginal children

20 Thank You!