Background

The causes of obesity in children are complex and currently not well understood. However, dietary intake, physical activity, socio-economic status, genetic influences and early social factors are thought to be important. Despite the increasing prevalence of obesity in children, few longitudinal studies are available to clarify these relationships. We are interested in dietary patterns that may lead to obesity and the factors influencing these dietary patterns.

Aims

The aims of this study are to conduct cross-cohort comparisons between the Western Australian Pregnancy (Raine) Cohort Study and ALSPAC, which are contemporaneous cohorts. We wish to compare the role of dietary patterns in obesity and the early determinants of obesogenic dietary patterns in these cohorts.

The Raine Study is a pregnancy cohort study of 2900 pregnant women recruited between 16 and 20 weeks of gestation through the public antenatal clinic and local private clinics in Perth, Western Australia from May 1989 till November 1991 (Newnham, et al, 1993 ). A total of 2868 children have been followed up at birth and ages 1, 2, 3, 5, 8, 10, 14 and 17 years. This study will be focusing on children at 14 and 17 years of age.

Specifically, we propose to:

1) Compare dietary patterns identified using reduced rank regression (RRR) in the Raine and ALSPAC cohorts

2) Test whether dietar patterns in the Raine study can predict obesity in ALSPAC children.

3) Identify and compare early life determinants of dietary patterns in ALSPAC and Raine cohorts. The early life determinants will include family structure and maternal education, parental pre-pregnancy body weight and BMI, maternal working hours, maternal smoking status during pregnancy and paternal smoking status. Identifying the early determinants of dietary patterns will help to identify target areas and developmental periods for improving dietary patterns.

Methods

1) Identify a dietary pattern using reduced rank regression (RRR) in the Raine cohort at 14 years of age, that explains the most variation in:

(i) dietary energy density (DED)

(ii) fibre density (FD)

(iii) percentage of total energy from fat

These particular dietary components are hypothesised to influence obesity risk.

2) Examine whether the dietary pattern identified in the Raine cohort predicts obesity in the Raine and ALSPAC cohorts. Using confirmatory RRR, we will apply the Raine dietary pattern identified at 14 years of age to ALSPAC food intakes collected at 13 years of age. Using linear regression and adjusting for appropriate confounders, we will examine prospective associations between applied dietary pattern scores at 13 y of age and obesity at 15 y of age in the ALSPAC cohort.

3) Identify early maternal and socio-demographic determinants of the Raine dietary pattern: analysis of variance (ANOVA) will be used to examine the variation in dietary pattern scores that is explained by early factors such as pre pregnancy BMI, maternal smoking status, maternal education, and maternal working hours. We propose to undertake the same analysis in the ALSPAC cohort to be able to compare the early determinants of the same dietary pattern in the Raine and ALSPAC cohorts.

ALSPAC data required for this project:

Food and nutrient intakes:

3-day food diaries completed at 13 years of age or FFQ data ?

Derived dietary intakes :

Cambridge food groups;

dietary energy density;

fibre density;

% energy from fat;

total energy intake;

misreporting of dietary intake (using Torun's method).

Anthropometry:

body mass index;

waist circumference;

fat mass;

pubertal stage;

birth weight and length;

gestational age

Physical activity:

accelerometer counts incl. moderate-vigorous activity

Socio-demographics:

child age;

child gender;

maternal age at birth;

maternal education;

maternal pre-pregnancy BMI;

maternal smoking status (pre pregnancy and up to 5 years later);

paternal smoking status;

maternal occupation and working hours;

family structure;

family functioning

Reference:

Newnham JP, Evans SF, Michael CA, Stanley JF, Landau LI. Effects of frequent ultrasound during pregnancy - a randomised controlled trial. Lancet 1993;342:887-91.