Zinc supplementation, mental development and behaviour in low birth weight term infants in northeast Brazil

Abstract

Objective: To test whether zinc supplementation reduces the deficits in mental development and behaviour that are found in term infants of low birth weight in the study population.

Design: A prospective double-blind, part-randomised efficacy trial.

Setting: A low-income population in Pernambuco, northeast Brazil, where the economy is largely dependent on sugar-cane production, and where over 90% of deliveries occur in health facilities.

Subjects: During a 20-month period, all singleton, term infants weighing 1500–2499 g born to families of low income (<US $280/month) were enroled at birth (n=205). At 6 and 12-months, the numbers tested were 163 and 138 respectively.

Intervention: Infants born from January 1993–January 1994 were randomly assigned to receive daily, except Sundays, a placebo (n=66) or 1 mg zinc (n=68). Those born February–August 1994 were given 5 mg zinc (n=71). Supplementation was for eight weeks, starting at birth. Field workers visited each infant at home to administer the supplement.

Results: At 6 and 12-months, mental and psychomotor development was assessed with the Bayley Scales of Infant Development and no significant differences in the scores of the three groups were found. At 12-months, behaviour was also assessed on 5 ratings. Ratings were highest in infants given 5 mg zinc (P=0.042).

Conclusions: Zinc supplementation (5 mg/d) for eight weeks may reverse some of the poor behaviours, particularly responsiveness, exhibited by low birth weight infants. No amelioration of their mental and psychomotor deficits was found.

Sponsorship: The Wellcome Trust, United Kingdom, provided financial support (Grant no. 036605/Z/92). Dr Lira was supported by CAPES (Fundação Coordenação de Aperfeiçoamento de Pessoal de Nível Superior), Brazil.