A Cochrane review [Abstract] 1 included 45 studies, with 9 cluster-RCTs. One study evaluating mortality included over one million children, and the remaining 44 studies included a total of 67 672 participants. Eight studies were in children known to be infected, and 37 studies were carried out in endemic areas, including areas of high (15 studies), moderate (12 studies), and low prevalence (10 studies). Albendazole (28 trials) and mebendazole (9 trials) were most commonly studied drugs.
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) increased weight gain over the next 1 to 6 months (5 studies, n=627). The effect size varied across studies from an additional 0.2 kg gain to 1.3 kg. There was insufficient evidence to know whether treatment had additional effects on haemoglobin (MD 0.10, 95% CI -0.65 to 0.86; 2 studies, n=247); school attendance (0 studies); cognitive functioning (2 studies, n=103), or physical well-being (3 studies, n=280).
Community deworming programmes: Treating all children living in endemic areas with a dose of deworming drugs had little or no effect on average weight gain (MD 0.04 kg less, 95% CI 0.11 kg less to 0.04 kg more; 7 studies, n=2 719), even in settings with high prevalence of infection (2 studies, n=290). A single dose also had no effect on average haemoglobin (MD 0.06 g/dL, 95% CI -0.05 lower to 0.17 higher; 3 studies, n=1 005), or average cognition (2 studies, n=1 361). Similiarly, regularly treating (every 3 to 6 months) all children in endemic areas with deworming drugs had little or no effect on average weight gain (MD 0.08 kg, 95% CI 0.11 kg less to 0.27 kg more; 10 studies, n=38 392); the effects were variable across studies. Regular treatment had no effect on average height (MD 0.02 cm higher, 95% CI 0.14 lower to 0.17 cm higher; 7 studies, n=7 057); average haemoglobin (MD 0.02 g/dL lower; 95% CI 0.08 g/dL lower to 0.04 g/dL higher; 7 studies, n=3 595); formal tests of cognition (5 studies, n=32 486); exam performance (2 studies, n=32 659); or mortality (RR 0.95, 95% CI 0.89 to 1.92; 3 studies, n=1 005 135). The findings were inconsistent on effect on school attendance (mean attendance 2% higher, 95% CI 4% lower to 8% higher; 2 studies, n=20 243). In a sensitivity analysis that only included trials with adequate allocation concealment, there was no evidence of any effect for the main outcomes.
Comment: The quality of evidence is downgraded by study quality (lack of/unclear allocation concealment and blinding) and by inconsistency (variability in results across studies).
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