Explaining differences in birth size and adiposity between Pakistani and white babies.

This study will examine differences in birth size between Pakistani and white babies. In the UK there are differences in birth size, body fat proportion and risk of heart disease and diabetes between south Asians and the general population. South Asians are more likely to be born small and develop heart disease and diabetes in later life. The processes of adult disease begin in early life, possibly even before birth. Despite their smaller size south Asian babies may have more body fat than white babies, which leads to their increased risk of disease as adults. I will clarify whether differences in the arrangement of body fat seen in south Asian adults, can be seen at birth. The study will use data and blood samples from the Born in Bradford project, a unique research programme following the lives of 10,000 babies born in the city between 2007 and 2009. In this study I will use data from 5,000 babies.The study will make a major contribution to efforts to tackle the burden of chronic adult disease in both white and south Asian populations.

Background
Low birth weight is recognised as an important predictor of child and adult health. In the UK there are marked differences in birth size between babies of south Asian origin and white babies. Babies born to south Asian families are generally lighter and it is unclear whether this difference reduces in second and third generations of UK south Asians. As adults south Asians have the highest mortality rate from coronary heart disease with much of the excess risk believed to be due to an increased risk of type 2 diabetes. For a given body mass index they are more centrally obese and are more likely to be insulin resistant. This has led to the suggestion that south Asians have a specific fat-thin insulin resistant phenotype. However relatively little is known about the fat-thin phenotype in south Asians living in the UK.
Aims
This proposal will take advantage of a newly funded bi-ethnic birth cohort study located in Bradford to examine differences in birth size and adiposity between 2500 white babies and 2500 Pakistani babies. Specifically this proposal aims to determine whether differences in birth anthropometry have reduced with subsequent generation immigrants, whether differences in size between white and Pakistani babies are detectable by ultrasound scan in the first, second and third trimester of pregnancy and whether there is evidence for the existence of the ‘fat-thin insulin resistant phenotype‘ at birth among Pakistani babies in comparison to white babies.
Design
Collection and analysis of data from a birth cohort study
Methods
This proposal will collect and analyse data from the Born in Bradford study, a new birth cohort study based at Bradford Teaching Hospitals NHS Trust which has secured funding and is due to begin recruiting participants in November 2006.This proposal will use data from 5000 mothers, fathers and their offspring (2500 white and 2500 Pakistani) who will be recruited in the first 18 months of the project. Data collection will include ultrasound assessment of fetal growth, birth anthropometry, cord blood samples, socio-economic status, lifestyle and country of origin data. Statistical analysis will apply Students t-tests and multivariable linear regression models to make comparisons between Pakistani and white babies. Power calculation: There will be 85-90% (or greater) power, at the 5% alpha level, to test all of the hypotheses proposed.