Malnutrition and mental development: Is there a sensitive period? A nestedcase-control study

To examine the possibility that there is an early sensitive period for the effects of malnutrition on cognitive development, three groups of children (N = 197) were recruited from a birth cohort with known growth characterist ics in south-west Ethiopia (N = 1563). All had initial weights greater than or equal to 2500g. Early growth falterers dropped in weight below the thir d centile (= < - 1.88) of the NCHS/WHO reference population in the first 4 months. Late growth falterers were children not in the first group whose we ights were below the third centile at 10 and 12 months. Controls were a str atified random sample with weights above the third centile throughout the f irst year. All children were tested blind at 2 years using the Bayley Scale s of Infant Development, adapted for use in Ethiopia. Mean (SD) scores on t he psychomotor scale were 10.2 (3.7) in the controls, 6.6 (4.2) in the earl y growth falterers, and 8.5 (4.3) in the late growth falterers. For the men tal scale they were 28.9 (5.8). 22.6 (6.2), and 26.6 (6.1) respectively. Bo th overall differences were statistically significant atp < .001, and plann ed comparisons between the control and the combined growth faltering groups , and between the early and later growth faltering groups, showed that each difference was statistically significant for both scales. However, early w eight faltering was associated with weight at the time of testing (r. =.33) , which was associated with scores both on the psychomotor (r =.53) and the mental scale (r=.49). After taking weight at the time of testing into acco unt there was no additional effect attributable to the timing of growth fal tering. In this population, therefore, early malnutrition does not have spe cific adverse effect beyond the contribution that it makes to enduring maln utrition over the first 2 years.