The researchers examined the effects of deworming children in areas where intestinal worm infection is common. After searching for relevant trials up to April 2015, they included 44 trials with a total of 67,672 participants, and an additional trial of one million children.
What is deworming and why might it be important
Soil-transmitted worms, including roundworms, hookworms, and whipworms, are common in tropical and subtropical areas, and particularly affect children in low-income areas where there is inadequate sanitation. Heavy worm infection is associated with malnutrition, poor growth, and anaemia in children.
The World Health Organization currently recommends that school children in endemic areas are regularly treated with drugs which kill these worms. The recommended drugs are effective at eliminating or greatly reducing worm infections, but the question remains whether doing so will reduce anaemia and improve growth, and consequently improve school attendance, school performance, and economic development, as has been claimed.
What the research says
In trials that treat only children known to be infected, deworming drugs may increase weight gain (low quality evidence), but we do not know if there is an effect on cognitive functioning or physical well-being (very low quality evidence).
In trials treating all children living in an endemic area, deworming drugs have little or no effect on average weight gain (moderate quality evidence), haemoglobin (low quality evidence), or cognition (moderate quality evidence).
Regular deworming treatment every three to six months may also have little or no effect on average weight gain (low quality evidence). The effects were variable across trials: one trial from 1995 in a low prevalence setting found an increase in weight, but nine trials carried out since then from moderate or high prevalence settings showed no effect.
There is good evidence that regular treatment probably has no effect on average height (moderate quality evidence), haemoglobin (low quality evidence), formal tests of cognition (moderate quality evidence), or exam performance (moderate quality evidence). We do not know if there is an effect on school attendance (very low quality evidence).
Treating children known to have worm infection may improve weight gain but there is limited evidence of other benefits. For routine deworming of school children in endemic areas, there is quite substantial evidence that deworming programmes do not show benefit in terms of average nutritional status, haemoglobin, cognition, school performance, or death.
This research is supported by the Department for International Development’s Evidence Building and Synthesis Research Programme which is led by Liverpool School of Tropical Medicine
Taylor-Robinson, D.C.; Maayan, N.; Soares-Weiser, K.; Donegan, S.; Garner, P. Deworming drugs for soil-transmitted intestinal worms in children: effects on nutritional indicators, haemoglobin and school performance. Cochrane Database of Systematic Reviews (2015) [DOI: 10.1002/14651858.CD000371.pub6]
Deworming drugs for soil-transmitted intestinal worms in children: effects on nutritional indicators, haemoglobin and school performance