Does Mass Deworming Affect Child Nutrition? : Meta-Analysis, Cost-Effectiveness, and Statistical Power
The WHO has recently debated whether to reaffirm its long-standing recommendation of mass drug administration (MDA) in areas with more than 20 percent prevalence of soil-transmitted helminths (hookworm, whipworm, and roundworm). There is consensus...
| Main Authors: | , , , , |
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| Format: | Working Paper |
| Language: | English en_US |
| Published: |
World Bank, Washington, DC
2017
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| Subjects: | |
| Online Access: | http://documents.worldbank.org/curated/en/926411482169164466/Does-mass-deworming-affect-child-nutrition-meta-analysis-cost-effectiveness-and-statistical-power http://hdl.handle.net/10986/25820 |
| Summary: | The WHO has recently debated whether to
reaffirm its long-standing recommendation of mass drug
administration (MDA) in areas with more than 20 percent
prevalence of soil-transmitted helminths (hookworm,
whipworm, and roundworm). There is consensus that the
relevant deworming drugs are safe and effective, so the key
question facing policymakers is whether the expected
benefits of MDA exceed the roughly $0.30 per treatment cost.
The literature on long run educational and economic impacts
of deworming suggests that this is the case. However, a
recent meta-analysis by Taylor-Robinson et al. (2015),
(hereafter TMSDG), disputes these findings. The authors
conclude that while treatment of children known to be
infected increases weight by 0.75 kg (95 percent CI: 0.24,
1.26; p=0.0038), there is substantial evidence that MDA has
no impact on weight or other child outcomes. This paper
updates the TMSDG analysis by including studies omitted from
that analysis and extracting additional data from included
studies, and finds that the TMSDG analysis is underpowered:
Power is inadequate to rule out weight gain effects that
would make MDA cost effective relative to comparable
interventions in similar populations, and underpowered to
reject the hypothesis that the effect of MDA is different
from the effect that might expected, given deworming's
effects on those known to be infected. The hypothesis of a
common zero effect of multiple-dose MDA deworming on child
weight at longest follow-up is rejected at the 10 percent
level using the TMSDG dataset, and with a p value < 0.001
using the updated sample. In the full sample, including
studies in settings where prevalence is low enough that the
WHO does not recommend deworming, the average effect on
child weight is 0.134 kg (95 percent CI: 0.031, 0.236,
random effects). In environments with greater than 20
percent prevalence, where the WHO recommends mass treatment,
the average effect on child weight is 0.148 kg (95 percent
CI: 0.039, 0.258). The implied average effect of MDA on
infected children in the full sample is 0.301 kg. At 0.22 kg
per U.S. dollar, the estimated average weight gain per
dollar is more than 35 times that from school feeding
programs as estimated in RCTs. Under-powered meta-analyses
are common in health research, and this methodological issue
will be increasingly important as growing numbers of
economists and other social scientists conduct meta-analysis. |
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