title: The relationship between early life modifiable risk factors for childhood obesity, ethnicity and body mass index at age 3 years: findings from the Born in Bradford birth cohort study.
abstract: BACKGROUND
  Many modifiable risk factors in early infancy have been shown to be associated with childhood overweight and obesity. These risk factors have not been studied within children of South Asian origin in the UK. The aims of this paper are to describe differences in the prevalence of modifiable risk factors for childhood obesity between children of White British and Pakistani origin and investigate the association between these risk factors and childhood BMI measured at age 3 years. We used data from a sub-study of the Born in Bradford birth cohort with detailed follow-up visits throughout early childhood. 987 participants with a BMI measurement at age 3 were included; 39% were White British, 48% were of Pakistani origin and 13% were of other ethnicities. Linear and Poisson regression models were used to assess the association between risk factors and two outcomes at age 3; BMI z-scores and child overweight.
  
  
  RESULTS
  Compared to Pakistani mothers, White British mothers were more likely to smoke during pregnancy, have higher BMI, breastfeed for a shorter duration and wean earlier, while Pakistani mothers had higher rates of gestational diabetes and were less active. There was no strong evidence that the relationship between risk factors and BMI z-score differed by ethnicity. There were associations between BMI z-score and maternal smoking (mean difference in BMI z-score 0.33 (95% CI 0.13, 0.53)), maternal obesity (0.37 (0.19, 0.55)), indulgent feeding style (0.15 (-0.06, 0.36)), lower parental warmth scores (0.21 (0.05, 0.36)) and higher parental hostility scores (0.17 (0.01, 0.33)). Consistent associations between these risk factors and child overweight were found. Mean BMI and the relative risk of being overweight were lower in children of mothers with lower parental self-efficacy scores and who watched more hours of TV. Other risk factors (gestational diabetes, child diet, child sleep, child TV viewing and maternal physical activity) were not associated with BMI.
  
  
  CONCLUSIONS
  Whilst the prevalence of risk factors that have been associated with childhood greater BMI differ between White British and Pakistani the magnitude of their associations with BMI are similar in the two groups.
authors.affiliation: Bradford Institute for Health Research, Bradford Teaching Hospitals NHS Foundation Trust, Duckworth Lane, BD9 6RJ Bradford, UK ; Faculty of Health Studies, University of Bradford, Bradford, UK.
authors.forename: Lesley
authors.initials: L
authors.lastname: Fairley
authors.affiliation: Clinical Trials Research Unit, University of Leeds, Leeds, UK.
authors.forename: Gillian
authors.initials: G
authors.lastname: Santorelli
authors.affiliation: MRC Integrated Epidemiology Unit at the University of Bristol, Bristol, UK ; School of Social and Community Medicine, University of Bristol, Bristol, UK.
authors.forename: Debbie A
authors.initials: DA
authors.lastname: Lawlor
authors.affiliation: Bradford Institute for Health Research, Bradford Teaching Hospitals NHS Foundation Trust, Duckworth Lane, BD9 6RJ Bradford, UK ; Clinical Trials Research Unit, University of Leeds, Leeds, UK.
authors.forename: Maria
authors.initials: M
authors.lastname: Bryant
authors.affiliation: Centre for Population Health Sciences, University of Edinburgh, Edinburgh, UK.
authors.forename: Raj
authors.initials: R
authors.lastname: Bhopal
authors.affiliation: Bradford Institute for Health Research, Bradford Teaching Hospitals NHS Foundation Trust, Duckworth Lane, BD9 6RJ Bradford, UK ; Faculty of Health Studies, University of Bradford, Bradford, UK.
authors.forename: Emily S
authors.initials: ES
authors.lastname: Petherick
authors.affiliation: Institute of Health and Well-being, Leeds Metropolitan University, Leeds, UK.
authors.forename: Pinki
authors.initials: P
authors.lastname: Sahota
authors.affiliation: Division of Biostatistics, University of Leeds, Leeds, UK.
authors.forename: Darren C
authors.initials: DC
authors.lastname: Greenwood
authors.affiliation: Institute of Health Sciences, Leeds University School of Medicine, Leeds, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Hill
authors.affiliation: School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, UK.
authors.forename: Noel
authors.initials: N
authors.lastname: Cameron
authors.affiliation: Parent-Infant Sleep Lab, Department of Anthropology, Durham University, Durham, UK.
authors.forename: Helen
authors.initials: H
authors.lastname: Ball
authors.affiliation: Bradford Institute for Health Research, Bradford Teaching Hospitals NHS Foundation Trust, Duckworth Lane, BD9 6RJ Bradford, UK.
authors.forename: Sally
authors.initials: S
authors.lastname: Barber
authors.affiliation: Bradford Institute for Health Research, Bradford Teaching Hospitals NHS Foundation Trust, Duckworth Lane, BD9 6RJ Bradford, UK.
authors.forename: John
authors.initials: J
authors.lastname: Wright
keywords: Body mass index; Born in Bradford; Early childhood risk factors; Ethnicity; Overweight