Insights from Africa’s largest and longest-running birth-cohort study
“During seven weeks in 1990, shortly after Nelson Mandela walked out of Victor Verster Prison a free man, 3273 children were born in Soweto and Johannesburg. We have followed these children and their families annually and sometimes biannually for 33 years to understand how their health and well-being changed as South Africa underwent political, social and economic transitions.”
“In conducting this study, we have grown, variously stumbled and succeeded, working in the cauldron of change, politics, miracles and misadventures that make our country the extraordinary place it is to live in and visit.”
“It’s a story about love – truly it is,” said Linda Richter.
Richter was presenting the fifth lecture in the 2023 STIAS Public Lecture Series.
Richter is a Developmental Psychologist and Distinguished Professor in the DSI-NRF Centre of Excellence in Human Development at the University of the Witwatersrand, South Africa, of which she was the inaugural Director. She has been a Visiting Scholar at Harvard, Melbourne and Oxford Universities, and from 2010-2012 was Advisor on Vulnerable Children at the Global Fund to Fight AIDS, Tuberculosis and Malaria in Geneva.
She led the research and drafting of South Africa’s National Integrated Early Childhood Development Policy, adopted in 2015, and the 2017 Lancet Series Advancing Early Child Development: From Science to Scale. She currently leads the ECD Countdown to 2030 and the linked country profiles, as well as the UKRI-funded project Harnessing Global Data to Advance Young Children’s Learning and Development. Linda has published over 330 papers in peer-reviewed journals and received Life-Time Achievement awards from both the South African Medical Research Council (SAMRC) and the National Research Foundation (NRF). She is an NRF A1-rated researcher.
Richter is one of the original investigators and the co-Principal Investigator (along with Shane Norris) of the South African birth-cohort study, Birth to Thirty (Bt30).
“She opened windows, let the fresh air in and rattled the cage of our culturally encapsulated world,” said Prof. Leslie Swartz of the Department of Psychology at Stellenbosch University in his introduction. “She is an engaged South Africa who cares and is not afraid to tackle the big questions without clear answers. She changed the lives of many.”
With 24 data-collection waves, 22 million raw data points, over 300 publications, two books and more than 50 post-graduate students mentored, the Bt30 project has produced vital information on biological, psychosocial and educational development, and broken new ground in conducting a study of this nature.
“It emerged from a progressive group of SAMRC and other researchers, and a confluence of threats and opportunities,” said Richter.
“The study was as ambitious as the country we wanted to create. Our first baby born was born on 23 April 1990 – as apartheid crumbled and the rainbow nation was born. They came to be known as Mandela’s Children.”
And it was ambitious with Richter pointing to the mechanics and funding needed to maintain a cohort over this period especially with a highly mobile population. But the challenge was met with sometimes ingenious retention strategies resulting in an overall attrition rate of under 40%.
There is also no doubt that such long-term studies produce extremely valuable information. Richter pointed to others including the Hertfordshire study in the UK which made the link between low birthweight and increased risk of cardiovascular disease in adulthood; a study on the post-World War II famine in The Netherlands which made the link between undernutrition in pregnancy and increased risk of schizophrenia in adulthood; British birth-cohort studies stretching back to 1946; and, the Harvard Study of Adult Development which enrolled students (including John F. Kennedy) during the Depression in the US and followed them up for 80 years which showed the importance of social bonds for increased life satisfaction, less anxiety and better health.
The value of measuring human lives
From the plethora of information produced by Bt30, Richter focused on some of the scientific results – a number of which have been taken up by policy makers.
“We showed a clear association between blood lead levels (measured in the umbilical cord) and violence in adolescence especially among male participants. In girls there was delayed onset of puberty. South Africa had the highest levels of lead in petrol until 2006. There was also a high usage of lead-based paint in homes. By 2009 there was legislative control, but compliance remains a problem.”
Bt30 showed clear links between maternal depression and anxiety and depression in adult offspring, as well as confirming the higher incidence of maternal depression in low- and middle-income countries (LMICs).
The study also tracked the rising prevalence of weight gain and obesity. “By age 41 50% of the mothers were obese,” explained Richter. “This is due to diets rich in refined fats and carbohydrates. Body mass index in the girls was twice as high as the boys.” She explained that obesity in women can lead to a host of health problems including infertility, miscarriage and gestational diabetes, as well as human and social costs.
The project also detailed important information on the origins of health and disease and the life-long effects of the first 1000 days of life. This work was done as part of a consortium involving five countries – Brazil, Guatemala, India, The Philippines and South Africa – including 22 840 pregnant women and children and 11 000 births with follow up to adulthood.
The work showed the importance of adequate nutrition during the first 1000 days for neuronal and cognitive development and thus human-capital development.
Emphasising the need to tackle undernutrition and stunting in LMICs, the studies showed the importance of early rather than later interventions. “Measuring growth at age five is too late. You need to intervene in the first two years of life,” explained Richer. “This can increase height and IQ with no negative trade-offs in chronic diseases. Catch-up growth after age two is linked with higher risk of later disease.”
The research also showed generational effects with a positive association between increased birthweight of mothers and birthweight of their grandchildren. But, importantly, it showed that beneficial nutritional effects are only evident when paired with other forms of stimulation. “Increased cognitive function is not achieved by nutritional intervention alone,” said Richter. “All interventions are necessary in a multisectoral effort to increase education and therefore economic capacity and wellbeing in adulthood.”
“We have been banging the drum about stunting for years,” she added. “It’s now being taken up. But stunting tells us about historical development not how to currently intervene. We shouldn’t lose the focus on stunting – it’s valuable information – but it shouldn’t be the only measure for how we move forward.”
“The real interventions need to happen pre-pregnancy and we need nutritional interventions for pregnant women and for the first six months. We also need to ensure cognitive stimulation. If the opportunity is not taken to enable babies to develop cognitively, it can be lost.”
She also pointed to the huge impact violence has had across the study (affecting both study staff and participants). “Violence permeates the lives of these children – only 1% had not witnessed violence and close to half of all participants had witnessed violence in their homes. We need to deepen the research and are looking at a possible collaborative study on violence.”
“We also looked at whether the hardships of apartheid continued post-1994. We found that 92% of participants live in a home with a fridge and TV, and 60% with a computer. But by age 28, 50% were still dependent on family,” she said. “The women were 1 cm taller than their mothers, 80% completed secondary school, and they were delaying childbirth. But there was more HIV, obesity, hypertension, psychological distress, substance abuse and interpersonal violence.”
Overall, Mandela’s Children experienced a complex burden of health and social challenges. Urbanisation and increasing socio-economic status meant that physical stature improved but changing diets led to an increase in weight and obesity linked to increasing chronic diseases. Although there was a decrease in some infectious diseases this group experienced the full onslaught of the HIV pandemic and rising gender-based and interpersonal violence.
“The last 30 years have had a huge impact on the lives of black South Africa children, but it is still insufficient to catch up with their white counterparts,” said Richter.
The full story of the science, the researchers and the participants is detailed in: Richter LM, Birth to Thirty. DSI-NRF Centre of Excellence in Human Development, University of the Witwatersrand and Reach Publishers, 2002. ISBN 978-1-77636-279-0.
Michelle Galloway: Part-time media officer at STIAS
Photograph: Ignus Dreyer