81 IGF-I and nutrition in preterm infants 4 Nutrient Intake in Relation to Concurrent IGF-1 Levels Positive associations were found between energy intake and IGF-1 levels at 30 to 33 weeks PMA (Table 5). BPD was a significant confounder from 32 weeks PMA. Protein, carbohydrate, and fat intake showed a similar pattern (Table 5). In addition, however, protein intake showed a positive association with IGF-1 levels at 28 weeks PMA: per gram increase in protein intake IGF-1 levels showed an increase of 1.1 nmol/L, R² = 0.506, p = 0.032. This is in contrast to a lack of associations at 29 weeks PMA with a larger sample size (n = 12) than the sample size at 28 weeks PMA. At 28 weeks PMA, IGF-1 was measured in six infants, of whom five had a recent history of sepsis and required an erythrocyte transfusion within 24 h of the blood sampling. Nutrient intake per kg body weight was not associated with IGF-1 levels at any point in time. After correcting for weight in multivariate analysis, the associations between total nutrient intake and IGF-1 lost their significance (Table 5). In univariate analysis at 30 weeks PMA, weight explained 45% of the variance in IGF-1 levels, compared to 33% of the variance that was explained by nutrient intake. By 33 weeks PMA, these numbers declined to respectively 17% and 15%. Nutrition in Relation to Changes in IGF-1 According to Postnatal Age The change in IGF-1 levels in the first four weeks of life was positively associated with protein, carbohydrate, fat, and total energy intake (after correction for gestational age). IGF-1 levels increased with 0.01 nmol/L per 10 kcal, R² = 0.266, p< 0.001. Comorbidities were not a significant confounder. After correcting for weight, total nutrient intake was no longer a significant predictor of change in IGF-1. Nutrition in Relation to Changes in IGF-1 According to Postmenstrual Age Looking at postmenstrual age, there was a positive association between total nutrient intake from 28 through 31 weeks PMA and the change in IGF-1 between birth and 32 weeks PMA (after correcting for gestational age). IGF-1 levels increased with 0.2 nmol/L per 10 kcal, R² = 0.287, p = 0.002. Comorbidities were not a significant confounder. However, after correcting for weight, energy intake could no longer predict the change in IGF-1. All macronutrients showed a similar pattern.
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