Sleep and physical growth in infants during the first 6 months.

The aim of this study was to explore the relationships between infant sleep patterns and infant physical growth (weight for length ratio) using both objective and subjective sleep measures. Ninety-six first-born, healthy 6-month-old infants and their parents participated in the study. Infant sleep was assessed by actigraphy for four consecutive nights and by the Brief Infant Sleep Questionnaire (BISQ). In addition, parents were asked to complete background and developmental questionnaires. Questions about feeding methods were included in the developmental questionnaire. Infants' weight and length were assessed during a standard checkup at the infant-care clinic when the infants were 6 months old. Significant correlations were found between infant sleep and growth after controlling for potential infant and family confounding factors. Actigraphic sleep percentage and reported sleep duration were correlated negatively with the weight-to-length ratio measures. Sex-related differences in the associations between sleep and physical growth were found. Breast feeding at night was correlated with a more fragmented sleep, but not with physical growth. These findings suggest that sleep is related significantly to physical growth as early as in the first months of life. The study supports increasing evidence from recent studies demonstrating a link between short sleep duration and weight gain and obesity in young children.