The Bt30 study is unique in that it is the largest and longest running study of child and adolescent health and development in Africa, as well as one of the few large-scale longitudinal studies in the world. A total of 3,273 singleton births were enrolled, beginning during the antenatal period with information also collected on pregnancy and birth. With a life-course approach, the study covers many of the major issues confronting the particular developmental phase of children and young people in which data is collected. In the early years, the emphasis was on environmental influences (poverty, migration, political violence), access to health services, nutrition and growth, childcare, and development. In the first few years of school, the emphasis was on cognitive ability, school performance, social adjustment, and inclusion. Later rounds of data collection explored early lifestyle risk factors: diet and weight gain, parental monitoring and supervision, educational failure, and sexual experimentation, and a wide range of physical (body composition and bone mineral density scans) and physiological measures (pubertal development, biochemical markers of insulin resistance) were introduced. Since their mid-teens, the study has focused on the prediction and measurement of risk, including: (i) sexual and reproductive behavior (sexual debut, unplanned pregnancy and sexually transmitted infections), (ii) early expression of the metabolic syndrome (obesity, hypertension, and insulin resistance) and (iii) social marginalization (school dropout, substance abuse, and conflict with the law).

As from October 2005, the next generation of children started to be born. While all the questionnaires used in Bt20 are being repeated with the third generation of children (called “3G”), an in-depth study of pregnancy is also underway with a focus on foetal maturation, and growth and development in the first two years of life. In these first “1,000 days” foetal and early programming plays a critical role in setting the stage for later childhood and adult health and well-being. Since 2006, Bt20 has collaborated in several joint analyses, including in the 2007 Lancet “Child Development” series. The most significant of these collaborations is the Consortium of Health Oriented Research in Transitioning Societies (COHORTS), a network between the five largest and longest running birth cohort studies in low and middle income countries (LMICs): Pelotas (Brazil), Guatemala, New Delhi, South Africa and the Philippines.

Research Themes

The overarching vision of Bt30 is to understand child and adolescent health and development. The research activities can be clustered into 8 themes:

• Infant, child and adolescent physical and mental health
• Influence of home, school and family environment on the child
• Sexual and other risk behaviours emerging during adolescence
• Body composition, obesity and emerging non-communicable disease risk
• Nutrition and bone health through childhood and adolescence
• Methodological issues around studying children and adolescents