Diet and infant behavior

We studied 142 preterm infants (mean gestation 31 weeks, mean birthweight 1364 g) fed prospectively varied protein and energy intakes. Infants were grouped as either slow or rapid growers based on rate of weight gain. Rapid growers had increased heart rates (166 vs 160 beats/min), respiratory rates (55.7 vs 53.9 bpm), energy expenditure (64.8 vs 61.6 kcal kg(-1) day(-1)), urinary C-peptide levels (1.59 vs 0.79 ng ml(-1)) and time in active sleep (78.0 vs 75.2%), and decreased spectral edge frequency in the electroencephalogram (2.96 vs 4.45 Hz) compared to slow growers. We conclude that preterm infants growing at varying rates manifest physiological and behavioral differences, and that these patterns may reflect altered autonomic balance.