Re-analysis of health and educational impacts of a school-based deworming programme in western Kenya: a pure replication

Aiken et al. (2014) usefully correct some errors in Miguel and Kremer (2004). Miguel and Kremer (2004) made two key claims: 1) deworming creates positive epidemiological externalities, thus causing estimates of the impact of deworming based on individual randomization to be biased downwards; and 2) deworming increases school participation. The results in Aiken et al. (2014) are consistent with these findings. In addition to direct impacts of deworming treatment on worm infections, Aiken et al. (2014) find externality effects within schools on untreated pupils, as well as externality effects across schools up to 3 km away. Similarly, with regard to school participation, both Miguel and Kremer (2004) and Aiken et al. (2014) find direct effects of deworming and externality effects within schools on untreated pupils. As Aiken et al. (2014) point out, most of the errors they identify (rounding errors or updates to the data set) lead to only small changes in estimated coefficients. The key change is that Miguel and Kremer (2004) measured externalities among schools located within 3-6 km that were among the 12 closest schools, rather than among all schools within 3-6 km, as reported; Aiken et al. (2014) report results including the full set of schools within 3-6 km. With the updated data, there is no evidence that worm infection externalities extend beyond the 12 closest schools to the full set of schools within 6 km, perhaps unsurprisingly given the local nature of disease transmission. We disagree with Aiken et al.'s (2014) conclusion that "there was no evidence of a between-school indirect effect" or an overall effect of deworming on school participation. We show that this conclusion is based on an approach that adds substantial noise to the estimation, by heavily weighting a non-significant 3-6 km externality estimate. This note addresses these and other points, and comments on the current state of deworming evidence. † Acknowledgements: We thank

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See 3 more Smart Citations

The end of the wormwars?

Tovey

Littell²,

Grimshaw³

2016

Deworming drugs for soil-transmitted intestinal worms in children: effects on nutritional indicators, haemoglobin, and school performance

Taylor-Robinson

Maayan²,

Soares‐Weiser³

et al. 2015

180

100

Background The World Health Organization (WHO) recommends treating all school children at regular intervals with deworming drugs in areas where helminth infection is common. As the intervention is often claimed to have important health, nutrition, and societal effects beyond the removal of worms, we critically evaluated the evidence on benefits. Objectives To summarize the effects of giving deworming drugs to children to treat soil‐transmitted helminths on weight, haemoglobin, and cognition; and the evidence of impact on physical well‐being, school attendance, school performance, and mortality. Search methods We searched the Cochrane Infectious Diseases Group Specialized Register (14 April 2015); Cochrane Central Register of Controlled Trials (CENTRAL), published in the Cochrane Library (2015, Issue 4); MEDLINE (2000 to 14 April 2015); EMBASE (2000 to 14 April 2015); LILACS (2000 to 14 April 2015); the meta Register of Controlled Trials ( m RCT); and reference lists, and registers of ongoing and completed trials up to 14 April 2015. Selection criteria We included randomized controlled trials (RCTs) and quasi‐RCTs comparing deworming drugs for soil‐transmitted helminths with placebo or no treatment in children aged 16 years or less, reporting on weight, haemoglobin, and formal tests of intellectual development. We also sought data on school attendance, school performance, and mortality. We included trials that combined health education with deworming programmes. Data collection and analysis At least two review authors independently assessed the trials, evaluated risk of bias, and extracted data. We analysed continuous data using the mean difference (MD) with 95% confidence intervals (CIs). Where data were missing, we contacted trial authors. We used outcomes at time of longest follow‐up. The evidence quality was assessed using GRADE. This edition of the Cochrane Review adds the DEVTA trial from India, and draws on an independent analytical replication of a trial from Kenya. Main results We identified 45 trials, including nine cluster‐RCTs, that met the inclusion criteria. One trial evaluating mortality included over one million children, and the remaining 44 trials included a total of 67,672 participants. Eight trials were in children known to be infected, and 37 trials were carried out in endemic areas, including areas of high (15 trials), moderate (12 trials), and low prevalence (10 trials). Treating children known to be infected Treating children known to be infected with a single dose of deworming drugs (selected by screening, or living in areas where all children are infected) may increase weight gain over the next one to six months (627 participants, five trials, low quality evidence ). The effect size varied across trials from an additional...

Public health deworming programmes for soil-transmitted helminths in children living in endemic areas

Taylor-Robinson

Maayan

Donegan

et al. 2019

Background The World Health Organization (WHO) recommends treating all school children at regular intervals with deworming drugs in areas where helminth infection is common. Global advocacy organizations claim routine deworming has substantive health and societal effects beyond the removal of worms. In this update of the 2015 edition we included six new trials, additional data from included trials, and addressed comments and criticisms. Objectives To summarize the effects of public health programmes to regularly treat all children with deworming drugs on child growth, haemoglobin, cognition, school attendance, school performance, physical fitness, and mortality. Search methods We searched the Cochrane Infectious Diseases Group Specialized Register; Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE; Embase; LILACS; the meta Register of Controlled Trials ( m RCT); reference lists; and registers of ongoing and completed trials up to 19 September 2018. Selection criteria We included randomized controlled trials (RCTs) and quasi‐RCTs that compared deworming drugs for soil‐transmitted helminths (STHs) with placebo or no treatment in children aged 16 years or less, reporting on weight, height, haemoglobin, and formal tests of cognition. We also sought data on other measures of growth, school attendance, school performance, physical fitness, and mortality. Data collection and analysis At least two review authors independently assessed the trials for inclusion, risk of bias, and extracted data. We analysed continuous data using the mean difference (MD) with 95% confidence intervals (CIs). Where data were missing, we contacted trial authors. We stratified the analysis based on the background burden of STH infection. We used outcomes at time of longest follow‐up. We assessed the certainty of the evidence using the GRADE approach. Main results We identified 51 trials, including 10 cluster‐RCTs, that met the inclusion criteria. One trial evaluating mortality included over one million children, and the remaining 50 trials included a total of 84,336 participants. Twenty‐four trials were in populations categorized as high burden, including nine trials in children selected because they were helminth‐stool positive; 18 with intermediate burden; and nine as low burden. First or single dose of deworming drugs Fourteen trials reported on weight after a single dose of deworming drugs (4970 participants, 14 RCTs). The effects were variable. There was little or no effect in studies conducted in low and intermediate worm burden groups. In the high‐burden group, there was little or no effect in most studies, except for a large effect detected from one study area in Kenya reported in two trials carried out over 30 years ago. These trials result in qualitative hete...