Pre-pregnancy body mass index and breastfeeding initiation, early cessation and longevity: evidence from the first wave of the UK Millennium Cohort Study

Background International evidence indicates relationships between pre-pregnancy body mass index (BMI) and breastfeeding behaviours. This study aims to assess associations between key points in the breastfeeding trajectory (initiation, early cessation and longevity) and pre-pregnancy BMI in a recent, nationally representative British cohort. It also aims to explore in the British context potential moderation by mothers’ ethnic group. Methods The sample comprises 17 113 mothers from the UK Millennium Cohort Study who have information on pre-pregnancy BMI. Associations between pre-pregnancy BMI categories and breastfeeding initiation, early cessation and longevity are tested using logistic regression. Directed acyclic graphics identify appropriate minimal adjustment to block biasing pathways and classify total and direct effects. Results After adjusting for confounders, there are large differences in breastfeeding early cessation and longevity by pre-pregnancy BMI group. Differences in propensity to initiation are negligible. Having begun breastfeeding, overweight and obese mothers are more likely to cease in the first week and less likely to continue past 4 months. Observed potential mediators within pregnancy and delivery provide little explanation for relationships. Evidence for moderation by ethnicity is scant. Conclusions The causal mechanisms underlying relationships between pre-pregnancy overweight, obesity, and breastfeeding behaviours require further research. However, this study suggests pre-pregnancy BMI as one predictive measure for targeting support to women less likely to establish breastfeeding in the early days, and to continue beyond 4 months. The nature of support should carefully be considered and developed, with mind to both intended and potential unintended consequences of intervention given the need for additional investigation into the causes of associations

Socioeconomic inequalities in young children’s weight status in the UK

The high prevalence rates of child overweight and obesity within the UK is a serious problem, and one that has received a lot of attention from policy makers, researchers and the media. There is some evidence for socioeconomic inequalities in child overweight and obesity, with children in less advantaged socioeconomic groups at an increased risk of being overweight or obese. The nature of these inequalities is not well understood. Within this thesis I consider different aspects of socioeconomic status and their relationship with child overweight and obesity. There are three distinct strands of the investigation. Firstly, I consider whether socioeconomic inequalities in child overweight and obesity have changed over time. This is followed by two separate analyses of the relationship between obesity and overweight with parental income and education. I find evidence that socioeconomic inequalities in child overweight and obesity have widened over time, but only because of the relatively low increases in child overweight and obesity amongst children from the most advantaged families. I investigate whether there is an association between income and child overweight, and find that other parental characteristics, namely parental education, can explain correlations between familial income and child overweight and obesity. I find that father’s education has a stronger association with child overweight and obesity than does mother’s education, and that this is not solely because father’s education is a better predictor of the family’s financial and economic resources

Associations between socio-economic status (including school- and pupil-level interactions) and student perceptions of school environment and health in English secondary schools

This article examines interactions between school-level and pupil-level measures of socio-economic status for pupil reports of the school environment and a range of risk behaviours and health outcomes. The baseline survey for the INCLUSIVE trial provided data on pupil affluence and pupil reports of the school environment, smoking, drinking, anti-social behaviour at school, quality of life and psychological wellbeing for over 6,000 pupils (aged 11–12 years) in 40 schools within a 1-hour train journey from central London. The level of socio-economic disadvantage of the school was measured using the percentage of pupils eligible for free school meals. Multilevel regression models examined the association between pupil affluence, the socio-economic composition of the school and the interaction between these with the school environment, risk behaviours and health outcomes. Our findings provide some evidence for interactions, suggesting that less affluent pupils reported lower psychological wellbeing and quality of life in schools with more socio-economically advantaged intakes. There appears to be a complex relationship for anti-social behaviour. Where pupil affluence and school socio-economic composition were discordant, pupils reported a higher number of anti-social behaviours. This article provides further evidence that less affluent pupils are more likely to engage in a variety of risk behaviours and experience worse health outcomes when they attend schools with more socio-economically advantaged intakes, supporting some of the mechanisms described in the theory of human functioning and school organisation

Longitudinal deprivation trajectories and risk of cardiovascular disease in New Zealand

We used longitudinal information on area deprivation status to explore the relationship between residential-deprivation mobility and Cardiovascular Disease (CVD). Data from 2,418,397 individuals who were: enrolled in any Primary Health Organisation within New Zealand (NZ) during at least 1 of 34 calendar quarters between 1st January 2006 and 30th June 2014; aged between 30 and 84 years (inclusive) at the start of the study period; had no prior history of CVD; and had recorded address information were analysed. Including a novel trajectory analysis, our findings suggest that movers are healthier than stayers. The deprivation characteristics of the move have a larger impact on the relative risk of CVD for younger movers than for older movers. For older movers any kind of move is associated with a decreased risk of CVD

The three stages of building and testing mid-level theories in a realist RCT: a theoretical and methodological case-example.

BACKGROUND: Randomised controlled trials (RCTs) of social interventions are often criticised as failing to open the 'black box' whereby they only address questions about 'what works' without explaining the underlying processes of implementation and mechanisms of action, and how these vary by contextual characteristics of person and place. Realist RCTs are proposed as an approach to evaluation science that addresses these gaps while preserving the strengths of RCTs in providing evidence with strong internal validity in estimating effects. METHODS: In the context of growing interest in designing and conducting realist trials, there is an urgent need to offer a worked example to provide guidance on how such an approach might be practically taken forward. The aim of this paper is to outline a three-staged theoretical and methodological process of undertaking a realist RCT using the example of the evaluation of a whole-school restorative intervention aiming to reduce aggression and bullying in English secondary schools. DISCUSSION: First, informed by the findings of our initial pilot trial and sociological theory, we elaborate our theory of change and specific a priori hypotheses about how intervention mechanisms interact with context to produce outcomes. Second, we describe how we will use emerging findings from the integral process evaluation within the RCT to refine, and add to, these a priori hypotheses before the collection of quantitative, follow-up data. Third, we will test our hypotheses using a combination of process and outcome data via quantitative analyses of effect mediation (examining mechanisms) and moderation (examining contextual contingencies). The results are then used to refine and further develop the theory of change. CONCLUSION: The aim of the realist RCT approach is thus not merely to assess whether the intervention is effective or not, but to develop empirically informed mid-range theory through a three-stage process. There are important implications for those involved with reporting and reviewing RCTs, including the use of new, iterative protocols. TRIAL REGISTRATION: Current Controlled Trials ISRCTN10751359 (Registered 11 March 2014)

Differences in the risk of cardiovascular disease for movers and stayers in New Zealand: a survival analysis

Objectives: To explore if risk of cardiovascular disease (CVD) for participants who moved before their first CVD event is higher than for stayers, and examine whether the relationship is moderated by ethnicity. Methods: The sample comprised of 2,068,360 New Zealand (NZ) residents enrolled in any Primary Health Organisation, aged between 30-84 years, had complete demographic information, and no prior history of CVD. Cox proportional regression was used to compare CVD risk between movers and stayers. The analysis was conducted for the whole sample and stratified by ethnicity. Results: The combined analysis suggested movers have a lower risk of CVD than stayers. This is consistent for all ethnic groups with some variation according to experience of deprivation change following residential mobility. Conclusions: Although mobile groups may have a higher risk of CVD than immobile groups overall, risk of CVD in the period following a residential mobility event is lower than for stayers. Results are indicative of a short-term healthy migrant effect comparable to that observed for international migrants

Key elements of the research process during secondary analysis of the millennium cohort study: researching relationships between mothers’ pre-pregnancy body mass index and breastfeeding behaviors

In this case study, we describe some of the key analytical stages and decision-making processes during a research project comprising secondary analyses of the U.K. Millennium Cohort Study. Our work examined relationships between maternal body mass index (BMI) and breastfeeding behaviors. We discuss the development of our research: from familiarization with and appraisal of the proposed dataset; to choosing and recoding variables; to honing our conceptual framework and fitting the data to the research questions; to analysis, reporting, and discussing findings. While describing key stages, we also emphasize the iterative, messy, and nonlinear realities of conducting a research project using secondary data. We discuss crucial points to be aware of in this type of work and lessons learned: such as the need to update and revise coding, analyses, and interpretations in light of discussion, reflection, and external feedback