107 IGF-I, growth and body composition in preterm infants 5 Potential critical windows for IGF-I From birth to 4 weeks PNA a greater increase in IGF-I was associated with more fat free mass at term equivalent age. A similar association was seen for the change in IGF-I from birth to 36 weeks PMA. (table 7). Of the potential critical windows the change in IGF-I from birth to 4 weeks PNA, was the strongest predictor. (table 8) IGF-I levels were not associated with fat or fat free mass percentage. (table 7) Table 7. Associations between IGF-I and body composition at term age Fat mass term age r (95% CI)¹ Fat free mass term age r (95% CI)¹ Fat mass percentage term age B (95% CI)² Fat free mass percentage term age B (95% CI)² IGF-I 4 wks PNA 0.14 (-0.18 – 0.43) 0.53 (0.27 – 0.72) -0.2 (-1.0 – 0.5)a 0.2 (-0.6 – 1.0)b IGF-I 36 wks PMA 0.18 (-0.18 – 0.48) 0.16 (-0.19 – 0.47) 0.4 (-0.4 – 1.1)c 0.4 (-1.1 – -0.4)d IGF-I Term age 0.24 (-0.16 – 0.57)3 0.43 (0.06 – 0.69)3 0.0 (-0.5 – 0.5)e 0.0 (-0.5 – 0.5)f Change in IGF-I birth – 4 wks PNA 0.22 (-0.12 – 0.51) 0.59 (0.33 – 0.77) -2.5 (-35.7 – 30.7)g 2.2 (-32.1 – 36.5)h Change in IGF-I birth – 36 weeks PMA 0.23 (-0.04 – 0.47)4 0.33 (0.07 – 0.55)4 4.4 (-4.2 – 13.1) i4 -4.6 (-13.5 – 4.2)j4 Change in IGF-I from 30 weeks PMA onwards 0.06 (-0.21 – 0.32)4 0.03 (-0.24 – 0.30)4 2.0 (-3.0 – 7.1)k4 -2.2 (-7.4 – 3.0)l4 PMA: postmenstrual age, PNA: postnatal age Associations in bold were statistically significant p < 0.05. ¹ Correlations were controlled for gestational age at birth and postmenstrual age at time of body composition measurement ² Gestational age at birth and postmenstrual age at the time of body composition measurement were entered in the regression model as covariates 3 Also corrected for postmenstrual age at blood sampling 4 Not controlled for gestational age at birth, because gestational age did not correlate with change in IGF-I across PMA nor did it correlate with body composition. a R² 0.070, p 0.448; b R² 0.078, p 0.396; c R² 0.133, p 0.226; d R² 0.140, p 0.204; e R2 0.136, p 0.330; f R2 0.146, p 0.294; g R² 0.066, p 0.530; h R² 0.073, p 0.483; i R² 0.069, p 0.160; j R² 0.075, p 0.136; k R² 0.062, p 0.195; l R² 0.069, p 0.159;
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