Soil-transmitted helminth infection, loss of education and cognitive impairment in school-aged children: A systematic review and meta-analysis

Pabalan, Noel; Singian, Eloisa; Tabangay, Lani; Jarjanazi, Hamdi; Boivin, Michael J.; Ezeamama, Amara E. · 2018 · OpenAlex-citations

DOI: 10.1371/journal.pntd.0005523

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Summary

This systematic review and meta-analysis addresses the equivocal evidence regarding the impact of soil-transmitted helminth (STH) infections on the cognitive function and educational outcomes of school-aged children. Previous meta-analyses were limited to randomized controlled trials (RCTs) and often concluded that evidence for cognitive benefits of deworming was inconclusive. Motivated by criticisms of these prior reviews—such as poor trial quality, failure to account for rapid reinfection, and ethical concerns regarding placebo controls—this study re-examines the hypothesis that STH infection is associated with cognitive deficits and educational loss. It aims to provide a comprehensive assessment by including all primary epidemiologic studies, regardless of design, published between 1992 and 2016. The authors searched Medline, Biosis, and Web of Science for original studies in English, ultimately including 36 studies involving 12,920 children aged 5 to 20 years. The analysis categorized outcomes into six domains: four cognitive domains (learning, memory, reaction time, and innate intelligence) and two educational domains (school attendance and scholastic achievement). Pooled effects were calculated as standardized mean differences (SMD) comparing STH-infected/non-dewormed children against uninfected/dewormed counterparts. The study employed subgroup analyses based on study design, risk of bias (ROB), and co-prevalence of *Schistosoma* species. Methodological quality was assessed using the Cochrane tool for RCTs and a modified Newcastle-Ottawa Scale for observational studies. The results indicated that STH-infected or non-dewormed children exhibited small to moderate deficits in three cognitive domains: learning, memory, and innate intelligence (SMD: -0.44 to -0.27, P<0.01–0.03). No significant differences were found for reaction time, school attendance, or scholastic achievement in the overall pooled analysis. However, high heterogeneity was observed across all domains. Subgroup analyses revealed that deficits in learning persisted across various study designs and ROB levels, while deficits in memory, reaction time, and intelligence were significant primarily within observational studies and high ROB strata. In settings with co-prevalent *Schistosoma* infection, associations for deficits in learning, memory, and reaction time were stronger and statistically robust. Additionally, STH-related deficits in school attendance and scholastic achievement were noted in low and high ROB strata, respectively. The study concludes that there is empirical support for a cognitive and educational benefit of deworming, with STH-uninfected or dewormed children demonstrating superior performance in five of the six assessed domains. However, the authors caution that interpretation is limited by high risk of bias in some primary literature and significant between-study variability. The findings suggest that while deworming offers benefits, these may be enhanced by integrated, multi-pronged inter-sectoral strategies that address the environmental and structural roots of cognitive impairment and educational loss in developing regions.

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• cognitive capacity variation