Cómo Enfrentar el duelo: Así como la gente siente el duelo de muchas maneras diferentes, también lo maneja de manera diferente Algunas

Evidence about the nature o f the relationship between IDA and development is obtained from three types o f study. First, preventative studies where children are given iron supplementation, (usually in the form o f iron fortified formula), or placebo and their iron status and development monitored over a period o f time. Second, iron supplementation trials where anaemic children are given iron supplements or placebo and development is measured before and after treatment. Third, longitudinal studies o f children who took part in iron supplemention trials in infancy then followed up.

3.2.1 Preventative trials

This prospective design has the benefits o f randomisation and concerns about withholding treatment from anaemic children are allayed as subject selection is not by iron status. The disadvantage is that in trials o f iron fortified infant formula, changes in outcome may be due to iron, other components o f the formula or an interaction. However, they are useful studies as they consider the effects o f receiving a relatively cheap food item that many children have routinely. There are six studies o f this type in term infants. Four find significant associations between iron supplementation or fortification and/or haematological and developmental improvements (Heywood et al 1989, Moffatt et al 1994, Williams et al 1999, Stoltzfus et al 2001). The findings o f M offatt et al (1994) are weakened by attrition, about 20% o f the sample were lost before the first assessment and almost h alf by the last assessment. Heywood and colleagues (1989) found iron treatment was associated with improvement in haematologic indices but not development. Williams and colleagues’ study (1999) provides evidence that children in UK communities where anaemia is highly

prevalent might benefit developmentally from iron fortified formula. A recent study o f pre-school children in Zanzibar reported that iron supplementation was associated with improvements in language and motor development although the effect on motor scores was only seen in children who were <9.Og/dl haemoglobin concentration prior to the intervention (Stoltzfus et al 2001). In contrast, two studies find no association o f iron supplementation with development (de Andraca et al 1997, Morley et al 1999). Morley and colleagues (1999) found no developmental differences between any o f the groups, although the children were only tested when the intervention ceased, benefits might have been apparent later as in the study by Williams et al (1999). The influence o f iron on developmental scores is likely to be subtle; perhaps the children in the Williams trial were at a greater disadvantage, therefore they had a better and easier to measure response to the effects o f fortified formula. The Chilean study has yet to be fully reported (de Andraca et al 1997), but it is clear that treatment does not have positive effect on development. These studies are summarised in Appendix 1.

3.2.2 Iron supplementation trials

Randomised placebo controlled trials (RCTs) o f iron supplementation in anaemic children provide the strongest evidence o f the effects o f IDA on development because o f their design. If IDA causes developmental deficits these should be resolved if anaemic children are given iron. Post treatment changes should be compared with an anaemic placebo group to confirm that the effectiveness o f treatment and to control for any placebo and test practice effect. A number o f studies do not use a placebo

control design. The studies are summarised in Appendix 1. RCTs, unlike

observational studies, provide evidence o f cause preceding effect.

3.2.2.1 Studies with anaemic placebo controls

Three o f seven appropriately controlled supplementation studies found some evidence o f improvements in mental development after iron treatment (Oski & Honig 1978, Heywood et al 1989, Idjradinata & Pollitt 1993) and one o f motor development (Idjradinata & Pollitt 1993). A number o f studies reapplied psychological tests after a few days, (Oski & Honig 1978, Lozoff et al 1982, Lozoff et al 1987, W alter et al 1989), they are not intended for swift re-testing. Improvements could be due to practice or learning effects rather than a genuine improvement in abilities. Longer term studies allow time for the correction o f anaemia (Aukett et al 1986, Soewondo et

al 1989, Idjradinata & Pollitt 1993). This is important because to prove iron is the cause o f development disadvantage one must establish that iron therapy is statistically associated with resolution o f anaemia as well as improvement in deficits so providing a plausible explanation for the improvements.

Among the trials with longer-term supplementation, Soewondo and colleagues (1989) found no evidence that treatment was associated with developmental improvements. Explanations for this include a genuine lack o f a relationship between iron and development, insufficient treatment, the tests were not sensitive enough to pick up subtle deficits or that deficits do occur in certain cognitive processes but not in the ones measured. Idjradinata & Pollitt’s (1993) study o f four months iron therapy was hailed at the time as “the definitive contribution in this subject” (Wharton 1993). The authors present clear evidence that deficits in motor function are resolved in the anaemic treatment group and not in the anaemic placebo group. Furthermore the performance o f the treated group is similar to the non-anaemic children. It is less clear what the effects on mental functioning are as although the authors imply improvement, they omit the comparison that would show this.