title: Mass deworming to improve developmental health and wellbeing of children in low-income and middle-income countries: a systematic review and network meta-analysis.
abstract: Soil-transmitted helminthiasis and schistosomiasis, considered among the neglected tropical diseases by WHO, affect more than a third of the world's population, with varying intensity of infection. We aimed to evaluate the effects of mass deworming for soil-transmitted helminths (with or without deworming for schistosomiasis or co-interventions) on growth, educational achievement, cognition, school attendance, quality of life, and adverse effects in children in endemic helminth areas.
  
  
  
  We searched 11 databases up to Jan 14, 2016, websites and trial registers, contacted authors, and reviewed reference lists. We included studies published in any language of children aged 6 months to 16 years, with mass deworming for soil-transmitted helminths or schistosomiasis (alone or in combination with other interventions) for 4 months or longer, that reported the primary outcomes of interest. We included randomised and quasi-randomised trials, controlled before-after studies, interrupted time series, and quasi-experimental studies. We screened in duplicate, then extracted data and appraised risk of bias in duplicate with a pre-tested form. We conducted random-effects meta-analysis and Bayesian network meta-analysis.
  
  
  
  We included 52 studies of duration 5 years or less with 1 108 541 children, and four long-term studies 8-10 years after mass deworming programmes with more than 160 000 children. Overall risk of bias was moderate. Mass deworming for soil-transmitted helminths compared with controls led to little to no improvement in weight over a period of about 12 months (0·99 kg, 95% credible interval [CrI] -0·09 to 0·28; moderate certainty evidence) or height (0·07 cm, 95% CrI -0·10 to 0·24; moderate certainty evidence), little to no difference in proportion stunted (eight fewer per 1000 children, 95% CrI -48 to 32; high certainty evidence), cognition measured by short-term attention (-0·23 points on a 100 point scale, 95% CI -0·56 to 0·14; high certainty evidence), school attendance (1% higher, 95% CI -1 to 3; high certainty evidence), or mortality (one fewer per 1000 children, 95% CI -3 to 1; high certainty evidence). We found no data on quality of life and little evidence of adverse effects. Mass deworming for schistosomiasis might slightly increase weight (0·41 kg, 95% CrI -0·20 to 0·91) and has little to no effect on height (low certainty evidence) and cognition (moderate certainty evidence). Our analyses do not suggest indirect benefits for untreated children from being exposed to treated children in the community. We are uncertain about effects on long-term economic productivity (hours worked), cognition, literacy, and school enrolment owing to very low certainty evidence. Results were consistent across sensitivity and subgroup analyses by age, worm prevalence, baseline nutritional status, infection status, impact on worms, infection intensity, types of worms (ascaris, hookworm, or trichuris), risk of bias, cluster versus individual trials, compliance, and attrition.
  
  
  
  Mass deworming for soil-transmitted helminths with or without deworming for schistosomiasis had little effect. For schistosomiasis, mass deworming might be effective for weight but is probably ineffective for height, cognition, and attendance. Future research should assess which subset of children do benefit from mass deworming, if any, using individual participant data meta-analysis.
  
  
  
  Canadian Institutes of Health Research and WHO.
authors.affiliation: Bruyère Research Institute, Ottawa, ON, Canada; School of Epidemiology, Public Health and Preventive Medicine, University of Ottawa, Ottawa, ON, Canada. Electronic address: vivian.welch@uottawa.ca.
authors.forename: Vivian A
authors.initials: VA
authors.lastname: Welch
authors.affiliation: Bruyère Research Institute, Ottawa, ON, Canada.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Ghogomu
authors.affiliation: Cardiovascular Research Methods, University of Ottawa Heart Institute, Ottawa, ON, Canada.
authors.forename: Alomgir
authors.initials: A
authors.lastname: Hossain
authors.affiliation: Department of Pediatrics, King George's Medical University, Lucknow, India.
authors.forename: Shally
authors.initials: S
authors.lastname: Awasthi
authors.affiliation: Research Centre for Global Child Health and Child Health Evaluative Sciences, The Hospital for Sick Children, and Department of Nutritional Sciences, University of Toronto, Toronto, ON, Canada; Division of Epidemiology, Dalla Lana School of Public Health, Toronto, ON, Canada; Center of Excellence in Women and Child Health, Aga Khan University, Karachi, Pakistan.
authors.forename: Zulfiqar A
authors.initials: ZA
authors.lastname: Bhutta
authors.affiliation: Epidemiology Research Institute, Tropical Medicine Research Institute, The University of West Indies, Kingston, Jamaica.
authors.forename: Chisa
authors.initials: C
authors.lastname: Cumberbatch
authors.affiliation: Harvard Medical School and Harvard Pilgrim Healthcare Institute, Boston, MA, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Fletcher
authors.affiliation: School of Epidemiology, Public Health and Preventive Medicine, University of Ottawa, Ottawa, ON, Canada.
authors.forename: Jessie
authors.initials: J
authors.lastname: McGowan
authors.affiliation: London School of Hygiene & Tropical Medicine, London, UK.
authors.forename: Shari
authors.initials: S
authors.lastname: Krishnaratne
authors.affiliation: School of Psychology, Centre for Research on Educational and Community Services, University of Ottawa, Ottawa, ON, Canada.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Kristjansson
authors.affiliation: International Operation Canadian Red Cross Society, Ottawa, ON, Canada.
authors.forename: Salim
authors.initials: S
authors.lastname: Sohani
authors.affiliation: Bruyère Research Institute, Ottawa, ON, Canada.
authors.forename: Shalini
authors.initials: S
authors.lastname: Suresh
authors.affiliation: Bruyère Research Institute, Ottawa, ON, Canada; Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada.
authors.forename: Peter
authors.initials: P
authors.lastname: Tugwell
authors.affiliation: Campbell Collaboration, Oslo, Norway.
authors.forename: Howard
authors.initials: H
authors.lastname: White
authors.affiliation: School of Epidemiology, Public Health and Preventive Medicine, University of Ottawa, Ottawa, ON, Canada; Cardiovascular Research Methods, University of Ottawa Heart Institute, Ottawa, ON, Canada.
authors.forename: George A
authors.initials: GA
authors.lastname: Wells
mesh_terms: D000871:Anthelmintics / Q000627:therapeutic use*; D003071:Cognition; D006128:Growth; D006373:Helminthiasis / Q000188:drug therapy*; D006801:Humans; D007411:Intestinal Diseases, Parasitic; D012987:Soil; D015430:Weight Gain
chemical_list: D000871:Anthelmintics; D012987:Soil