Early fat-free mass gain in preterm infants is associated with school-age cognition.

BACKGROUND AND AIMS: Providing optimal nutrition to very preterm infants is a challenge, yet poor growth is associated with an increased risk for later developmental impairment. While nutritional support is mostly weight-directed, measuring Fat-Free Mass (FFM) and Fat Mass (FM) could provide better insight. We have investigated the association between preterm FFM accretion during the first months after admission and cognitive outcome at school age, and compared this with other growth metrics. METHODS: This study describes a prospective cohort of 100 preterm (<30wk gestational age) infants. Body composition (BC) was measured using PEAPOD® at corrected age (CA) 6 weeks and 6 months. Cognitive outcomes were assessed with WPPSI-III-NL at 5.5 years CA. Multiple linear regression was used for the association between BC and cognitive outcomes at 5.5 years, adjusted for baseline factors. RESULTS: FFM z-scores at 6 wk (B = 6.15 [95% CI 1.50-10.80]) and 6 mo (B = 6.04 [95% CI 2.20, 9.87]) CA, as well as FFM accretion rate (g/week, B = 0.37 [95% CI 0.18-0.58]), were significantly associated with Full Scale IQ (FSIQ) scores at 5.5 years CA, independent of head circumference. FM, height and weight measures showed no significant association at 6 mo. The association of FFM versus FSIQ at 6 mo remained robust after adjusting for birthweight and neonatal illness, while it attenuated for 6 wk. Children with persisting low FFM z-scores between the two visits had low FSIQ (79.2 ± 17.3), while those who increased to normal before 6mo, had age-adequate IQ scores (96.7 ± 16.9). CONCLUSION: FFM accretion in early infancy is associated with school-age cognition in very preterm infants, surpassing traditional weight or FM metrics. Incorporating monitoring FFM alongside head circumference could improve developmental risk stratification.