Deworming improves child cognition. Eventually.


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You could be forgiven if you found deworming to be something of an enigma. Some have hailed it as one of the most cost-effective interventions for improving school participation in developing countries. Yet two recent review papers, drawing together the lessons from many studies, find insignificant effects of deworming on learning specifically and only uncertain evidence on cognition more generally. How could this be?

The short answer is that, until a few months ago, both views could be right. Allow me to explain.

Deworming treats a group of neglected tropical diseases caused by parasitic worms. They are generally not lethal, but they live for the most part in the human gut, and absorb key nutrients (including iron) that would otherwise be nourishing their human hosts. Not long ago, widespread worm infections were problematic not only in the tropics and developing world, but in rich countries as well. Where sanitation was poor, parasitic worms flourished. When, early in the 20th century, a treatment campaign was rolled out in the American South, it increased school attendance and literacy.

This study of deworming in the American South is a rarity. We simply don’t have many studies of the impact of deworming on cognition and learning. These outcomes don’t change overnight, so only long-run studies are well-positioned to uncover any effects. Without many studies, reviews of the literature are bound to come up short.

To make matters worse, the epidemiology of worm infections may have frustrated many early attempts at answering the question at hand. Treating one person’s infections helps everyone around that person by reducing the chance that they are newly infected. This means that studies comparing neighbors who did and didn’t receive deworming drugs could find small effects, in part because untreated study participants actually benefit from medications that their neighbors take (i.e., they don’t get worms from their neighbors). This means that – despite appearances – in many older studies, there simply was no real control group that was not impacted by the intervention.

That is where things stood, a few months ago.

But a handful of researchers (myself included) had undertaken long-term follow-ups of cluster-randomized deworming studies. Cluster-randomized means that whole communities were (or weren’t) given deworming medications, overcoming the methodological problem that frustrated earlier work. Now, the results are available for all to see.

Kevin Croke follows children who received deworming medication through Child Health Days in Uganda from 2000-2003 (initially studied by Harold Alderman and co-authors), and finds that 10 years later, children who received deworming medication do better on mathematics tests.

Sarah Baird, Joan Hamory Hicks, Michael Kremer, and Edward Miguel follow children who began receiving deworming medication in Kenyan schools in the late 1990s, and 10 years later, find improvements in educational outcomes for women, as well as a variety of beneficial labor market impacts for both genders.

And in my work, I go one step further: Ten years after the deworming, I found the children who were in infancy when the deworming was conducted in those same Kenyan communities, and who didn’t receive treatment at the time. I looked for them because we know that health in early childhood can have lasting implications. And because the schoolchildren in their communities were dewormed in the late 1990s, infants in those communities faced lower rates of infection than they otherwise would have. I conducted surveys and cognitive tests of these children 10 years later to find out whether their improved health in early childhood – thanks to the deworming of their older siblings and neighbors – had a long-term effect on their cognition. It did. Children whose communities were dewormed before they were 1 year old perform markedly better on tests of reasoning than their counterparts in communities where deworming began later. Remember, in early childhood, these children were not treated directly; they just reaped the spillover benefits of fewer worms in their communities. At this critical period in child development, the effect of deworming is long-lasting and easy to see.

The new evidence has already led to some re-evaluation of the findings about deworming; it looks like it has cognitive benefits, after all.
Ozaveshe Ade Balogun
October 17, 2014

If deworming processes are so beneficial to both infants and children, it will go a long way to reduce risk of infections then, it is worth doing. African nations in particular must create the needed awareness for parents to deworm their children as recommended to avoid unnecessary future health challenges the children might be subjected to.
Slum/ghetto settlements should be made to compulsorily undergo deworming processes as often as may be required by medical experts. After all a healthy nation is a prosperous nation.
I commend the researchers for this good job they have done on deworming infants and children.

dr. james sika, maseno university
November 08, 2014

The result may have a bearing in Kenya where deworming campaign has been on for two years now. The result being collaborated may impact on health issues affecting cognitive development of our children. The immediate impact has been school attendance which has been o increase, increase parental awareness, appreciation by the surrounding community, support by educational officials. However academic performance and cognitive achievement has be quantified to realize the expected results

October 20, 2014

Very interesting and important work!

November 03, 2014

With African nations facing so many hardships, especially with the outbreak of Ebola, any potential health and cognitive benefit seems worth doing to improve conditions. The results of this study are very interesting and pose a wonderful opportunity for communities to reduce illness caused by worms, both direct and indirectly, as well as strengthen academic participation and cognition. Providing deworming medication should be established, especially in communities suffering from malnourishment and unsanitary settlements, not just for the academic benefits, but also for the ability for bodies to absorb all the nutrients they consume versus nourishing the parasitic worms. It would be interesting to compare the health (body weight) and hunger levels of dewormed communities versus clusters of settlements that did not receive the treatment.
Miami University, OH