How poverty affects brain, child development
An unprecedented study in Bangladesh, published July 12, 2017, in journal revealed how malnutrition, poor sanitation and other challenges make their mark on child development.
IN the late 1960s, a team of researchers began doling out a nutritional supplement to families with young children in rural Guatemala. They were testing the assumption that providing enough protein in the first few years of life would reduce the incidence of stunted growth.
It did. Children who got supplements grew 1 to 2 centimetres taller than those in a control group. But the benefits didn't stop there. The children who received added nutrition went on to score higher on reading and knowledge tests as adolescents, and when researchers returned in the early 2000s, women who had received the supplements in the first three years of life completed more years of schooling and men had higher incomes.
“Had there not been these follow-ups, this study probably would have been largely forgotten,” says Reynaldo
Martorell, a specialist in maternal and child nutrition at Emory University in Atlanta, Georgia, who led the follow-up studies. Instead, he says, the findings made financial institutions such as the World Bank think of early nutritional interventions as long-term investments in human health.
Since the Guatemalan research, studies around the world — in Brazil, Peru, Jamaica, the Philippines, Kenya and Zimbabwe — have all associated poor or stunted growth in young children with lower cognitive test scores and worse school achievement.
A picture slowly emerged that being too short early in life is a sign of adverse conditions — such as poor diet and regular bouts of diarrhoeal disease — and a predictor for intellectual deficits and mortality. But not all stunted growth, which affects an estimated 160 million children worldwide, is connected with these bad outcomes. Now, researchers are trying to untangle the links between growth and neurological development. Is bad nutrition alone the culprit? What about emotional neglect, infectious disease or other challenges?
Shahria Hafiz Kakon is at the front line trying to answer these questions in the slums of Dhaka, Bangladesh, where about 40 per cent of children have stunted growth by the age of two. As a medical officer at the International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b) in Dhaka, she is leading the first-ever brain-imaging study of children with stunted growth. “It is a very new idea in Bangladesh to do brain-imaging studies,” says Kakon.
The research is innovative in other respects, too. Funded by the Bill & Melinda Gates Foundation in Seattle, Washington, it is one of the first studies to look at how the brains of babies and toddlers in the developing world respond to adversity. And it promises to provide important baseline information about early childhood development and cognitive performance.
Kakon and her colleagues have run magnetic resonance imaging (MRI) tests on two- and three-month-old children, and identified brain regions that are smaller in children with stunted growth than in others. They are also using other tests, such as electroencephalography (EEG).
“Brain imaging could potentially be really helpful” as a way to see what is going on in the brains of these young children, says Benjamin Crookston, a health scientist at Brigham Young University in Provo, Utah, who led studies in Peru and other low-income countries that reported a link between poor growth and cognitive setbacks.
In 2006, the World Health Organization (WHO) reported an extensive study to measure the heights and weights of children between birth and the age of five in Brazil, Ghana, India, Norway, Oman and the United States. The results showed that healthy, well-fed children the world over follow a very similar growth trajectory, and it established benchmarks for atypical growth. Stunted growth, the WHO decided, is defined as two standard deviations below the median height for a particular age. Such a difference can seem subtle. At six months old, a girl would be considered to have stunted growth if she was 61 centimetres long, even though that is less than five centimetres short of the median.
The benchmarks helped to raise awareness about stunting. In many countries, more than 30 per cent of children under five meet the definition; in Bangladesh, India, Guatemala and Nigeria, over 40 per cent do. In 2012, growing consensus about the effects of stunting motivated the WHO to pledge to reduce the number of children under five with stunted growth by 40 per cent by 2025.
Even as officials started to take action, researchers realized there were serious gaps in protocols to identify the problems related to stunting. Many studies of brain development relied on tests of memory, speech and other cognitive functions that are ill-suited to very young children. “Babies do not have much of a behavioural repertoire,” says Michael Georgieff, a paediatrician and child psychologist at the University of Minnesota in Minneapolis. And if parents and doctors have to wait until children are in school to notice any differences, it will probably be too late to intervene.