Prevention of diarrhea and pneumonia by zinc supplementation in children in developing countries: Pooled analysis of randomized controlled trials

Objectives: This study assessed the effects of zinc supplementation in the prevention of diarrhea and pneumonia with the use of a pooled analysis of r andomized controlled trials in children in developing countries. Study design: Trials included were those that provided oral supplements con taining at least one half of the United States Recommended Daily Allowance (RDA) of zinc in children <5years old and evaluated the prevention of serio us infectious morbidity through household visits. Analysis included 7 "cont inuous" trials providing 1 to 2 RDA of elemental zinc 5 to 7 times per week throughout the period of morbidity surveillance and 3 "short-course" trial s providing 2 to 4 RDA daily for 2 weeks followed by 2 to 3 months of morbi dity surveillance. The effects on diarrhea and pneumonia were analyzed over all and in subgroups defined by age, baseline plasma zinc concentration, nu tritional status, and sex. The analysis used random effects hierarchical mo dels to calculate odds ratios (OR) and 95% CIs. Results: For the zinc-supplemented children compared with the control group in the continuous trials, the pooled ORs for diarrheal incidence and preva lence were 0.82 (95% CI 0.72 to 0.93) and 0.75 (95% CI 0.63 to 0.88), respe ctively. Zinc-supplemented children had an OR of 0.59 (95% CI 0.41 to 0.83) for pneumonia. No significant differences were seen in the effects of the zinc supplement between the subgroups examined for either diarrhea or pneum onia. In the short-course trials the OR for the effects of zinc on diarrhea l incidence (OR 0.89, 95% CI 0.62 to 1.28) and prevalence (OR 0.66, 95% CI 0.52 to 0.83) and pneumonia incidence(OR 0.74, 95% CI 0.40 to 1.37) were si milar to those in the continuous trials. Conclusions: Zinc supplementation in children in developing countries is as sociated with substantial reductions in the rates of diarrhea and pneumonia , the 2 leading causes of death in these settings.