positive cognitive benefits consistently over a number of studies (Grantham-McGregor and Ani,
2001; Sachdev et al, 2005). There are a number of large-scale trials on iron supplementation
in infants or young children in developing countries, including Zanzibar (Stoltzfus et al 2001),
Chile (Lozoff et al, 2003), Bangladesh (Black et al, 2004), Indonesia (Lind et al, 2003) and India
(Black et al, 2002). Four of these aforementioned studies include infants at risk for stunting,
while the fifth includes well nourished infants. All five studies report positive benefits of iron
supplementation for motor skills, while the studies in India, Bangladesh and Chile also report
social-emotional benefits. Finally, the Zanzibar and Chile studies also demonstrate cognitive
language benefits for children receiving iron supplementation. It is worth noting that the
Chilean study yields the largest number of beneficial outcomes, and this was the only study to
target healthy infants. 12This simply serves as a reminder that the outcome of an intervention
will in part be a function of the characteristics of the target population.
Bobonis et al (2002) report results from the Balwadi Health project in India, in which they
evaluate the impact of a non-governmental organization (NGO) pre-school nutrition and health
project implemented in Delhi. This programme provides iron supplementation and deworming
drugs to over 4000 children aged 2-6 years, through an existing pre-school network. The pre-
schools in the study were randomly divided into three groups, and the schools were gradually
phased into the program as it expanded over the course of two years. The results to date show
that children in treatment schools gained significant weight (0.6 kgs on average) compared
to children in control schools, and that average pre-school participation rates increased by 6.3
percentage points among assisted children, reducing pre-school absenteeism by roughly one-fifth.
Moreover, they found an almost 50% reduction in the incidence of severe to moderate anemia.
The longer-term benefits of iron supplementation are less clear, mainly due to insufficient
evidence. The large scale randomised trials suggest that cognitive, social, emotional and motor
development can all be positively affected by iron supplementation, at least in the short run,
which is promising in terms of longer term effects.
In addition to potential effects on school attendance, there is evidence that suggests that
iron supplements have a large effect on productivity of adult workers. Basta et al. (1979),
found increased work output among anemic workers in Indonesia who were given iron supple-
ments. However, while this study was a randomized controlled trial, their estimates are likely
biased upwards due to problems of attrition. Another large-scale study of iron supplements in
Indonesia found gains in adult productivity (as measured by earnings) especially among those
who already had low hemoglobin levels (Thomas et al 2003).
7.1.3 Deworming
Illness due to worms is a problem that affects approximately one third of the worlds popu-
lation, and the incidence of such infection is highest amongst school-aged children (Watkins
and Pollitt, 1987). There are relatively few studies of the impact of worm infections on child
development, and particularly for pre-schoolers, but arguably, poor health due to geohelminth
infections not only has negative health effects but may also limit participation in pre-school
activities. Hutchinson et al (1997) conduct a cross-sectional study of 800 children aged 9-13 in
Jamaica and find an association between low academic achievement and mild levels of malnu-
trition and geohelminth infections. Oberhelman et al (1998) demonstrate a correlation between
geohelminth infections and poor language development, while Callander et al (1998) show that
treatment of children with trichuris dysentery syndrome produced improvements in mental and
motor development after 4 years. These kinds of statistical associations suggest a compelling
case for interventions aimed at improving school performance in developing countries to target
the health and nutritional status of children. Bleakley (2007) finds that hookworm eradication
campaigns in the southern United States in the early 1900s resulted in increased school enroll-
ment and attendance. In that study, adults exposed to the deworming campaign as children
12It is possible that additional benefits were not seen in the other studies that targeted at-risk infants if these
additional benefits required complementary activities, such as parental stimulation, nutritional supplements and
so on.
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