1. Impact of Nutritional and Non-Nutritional Factors on Fat-Free Mass In Very Low Birth Weight Infants PATRICK MCCARTHY, MD CANDIDATE, 1 HEATHER GRAY, MPH 2, ELLEN W DEMERATH, PhD 2, MICHAEL GEORGIEFF, MD 1, SARA RAMEL, MD 1 1 Department of Pediatrics, University of Minnesota, Minneapolis, MN, United States and 2 Department of Epidemiology and Community Health, University of Minnesota, Minneapolis, MN, United States Disclosure statement: Dr. Ellen Demerath has received grant funding from COSMED (Peapod Manufacturer) Results Background: While postnatal weight gain is a concern in preterm infants, organ growth and differentiation (eg, the brain) is more closely linked to linear growth and fat-free mass (FFM). Poor extrauterine linear growth is associated with lower cognitive function beyond infancy. Preterm infants have decreased FFM and increased fat mass at term corrected gestational age compared to term counterparts. This discrepancy is thought to be secondary to early nutritional deprivation and physiological stress, however the mechanism and long-term consequences of this altered body composition are not well understood. Objective: This study investigates how early nutrition and illness in the very low birth weight (VLBW) neonate affect later body composition. Design/Methods: In this prospective study, anthropometric measurements and body composition testing via air displacement plethysmography were performed on VLBW infants at hospital discharge (n=41; mean discharge age = 37.9 +/- 2.8 weeks) and at 4 months of age corrected for prematurity (CA) (n=26). During hospital stay, markers of illness (days requiring any use of steroids, respiratory support, or oxygen) as well as macronutrient deficits (protein and caloric) were recorded. Results: At discharge, greater number of days of steroid administration was associated with decreased FFM (p=0.001). Increased days of critical illness and caloric deficit during hospital stay correlated with significantly lower FFM at 4 months CA (steroids, p=0.04; respiratory support, p=0.02; oxygen, p=0.03; caloric deficit, p=0.01). Significantly shorter lengths at 4 months CA were associated with steroid use and caloric deficit. Neither fat mass nor weight was found to vary according to any marker of illness or macronutrient deficit. Protein deficit was not associated with FFM or length at either time point. Conclusions: FFM, a key marker for organ growth and development, indexes a number of clinical factors that reflect the interplay between critical illness and malnutrition in the VLBW neonate. The delayed nature of these effects seen only at 4 months CA may reflect long-term disruptions to the growth hormone/insulin- like growth factor-1 axis or insufficient nutrient intake following discharge. Additional studies are needed to elucidate the effects of illness on growth factors and protein accretion in order to inform nutrition management in VLBW neonates with particular consideration of FFM.  SAMPLE: 56 appropriate for gestational age VLBW (<1500g) preterm infants  MEASURES: Weight, length, head circumference and body composition (fat mass, fat free mass and percent body fat) using air-displacement plethysmography (Pea Pod, COSMED USA) were collected at discharge and at 4 months corrected age (CA). Data were also gathered on several clinical markers of illness. Total hospital caloric and protein deficits were calculated by taking the total amounts received throughout hospitalization and subtracting it from a calculated goal of 120 kcal/kg/day and 3.5 g of protein/kg/day, respectively.  STATISTICAL ANALYSIS: Linear regression analysis was performed to assess associations between indicators of nutritional and clinical stressors and growth markers. Adjustment was made for infant sex, age at visit, gestational age, and kcal deficit depending on the regression model used. Individuals with missing data at a time point were dropped from analysis at that time point. Abstract Background Methods Objective Table 1. Anthropometric and body composition characteristics at birth, Hospital discharge and 4 Months CA in 56 AGA VLBW preterm infants Table 2. Markers of illness and nutritional status in 56 AGA VLBW preterm infants  Linear growth and fat-free mass (FFM) are closely linked to organ development and differentiation and are thus important growth parameters for the study of nutritional and physiological stressors on the preterm infant.  Preterm infants have elevated fat mass and diminished FFM when compared to term counterparts at hospital discharge (Ramel et al). Excess early growth and body disproportionality may increase the risk of adverse neurologic and metabolic sequelae. In addition, poor linear growth is associated with poor neurocognitive outcomes in preterm infants as well as in deprived settings globally.  Factors in addition to nutrient delivery may be key to growth optimization in the very low birth weight (VLBW) preterm infant. While previous research has focused on calorie and protein intake, little is known about the impact of critical illness and clinical interventions on the growth and body composition of this population. To investigate how early nutrition and markers of critical illness in the VLBW neonate affect later linear growth and body composition. Summary & Conclusions  FFM and length, key markers of organ growth and development, are influenced by energy intake and several clinical markers of critical illness and inflammation out to at least 4 months CA.  Postnatal steroid use has an association with diminished linear growth and FFM gains well beyond the period of administration and independent of caloric deficit. This is likely secondary to the effect of steroids on protein accretion and may be a potential mechanism for the association between steroids and poorer long-term neurodevelopmental outcomes.  Additional studies are needed to determine the relative contributions of illness and malnutrition to growth factors and protein accretion to inform nutritional and clinical management of VLBW preterm infants. References & Acknowledgement Ramel SE, Gray H, Larson Ode K, Georgieff M and Demerath EW. Body Composition Changes in Preterm Infants Following Hospital Discharge: A Comparison to Term Infants. J Pediatr Gastroenterol Nutr. 2011; 53(3): 333-8. This study was funded by the Amplatz Scholar Award. We acknowledge Bridget Davern, Heather Wanous, and Jenni Super for their assistance in data collection and enrollment.  Protein deficit was not associated with any measured growth parameter at either time point.  Aggressive nutritional support was provided resulting in minimal nutritional deficits.  Inflammation and steroid use affect protein accretion and appear to influence FFM accretion and linear growth more strongly than intake alone. These associations persist until at least 4 months CA.  Interventions aimed at decreasing inflammation while limiting postnatal steroid administration may improve FFM gains and linear growth in this vulnerable population.  Several markers of critical illness/inflammation during hospitalization are associated with FFM and linear growth both at hospital discharge and 4 months CA.  This prolonged effect on growth may reflect long-term alterations to the growth hormone/IGF-1 axis or post-discharge nutritional deficiencies.  Following adjustment for caloric deficit, only steroid administration retained a significant impact on growth indices. Discussion Figure 2. Relative contributions of illness and malnutrition on length at Discharge & 4 months CA in AGA VLBW preterm infants Figure 1. Relative contributions of illness and malnutrition on FFM at Discharge & 4 months CA in AGA VLBW preterm infants Table 4. Association of multiple nutritional and clinical variables with length at discharge and 4 months corrected age Table 3. Association of multiple nutritional and clinical variables with fat-free mass at discharge and 4 months corrected age Length at Discharge Length at 4mo CA Fat Free Mass at Discharge Fat Free Mass at 4mo CA