Associations Between Breast Milk Energy Intake, Infant Sleep Duration and Time Until Next Feed.

BACKGROUND: Sleep in early infancy supports neurodevelopment, yet the influence of breast milk composition on sleep duration remains unclear. OBJECTIVE: To determine whether breast milk energy intake is associated with the duration and timing of subsequent infant sleep episodes. METHODS: Thirty-four healthy, fully breastfeeding mother-infant dyads (infant age: 3.7 ± 1.3 months) recorded 24-h infant feeding and sleep data, with feed volumes measured by pre- and post-feed test-weighing. Milk samples were collected and analysed for macronutrient concentrations to calculate energy intake per feed. Linear mixed-effects models were used to examine whether energy intake from the preceding feed was associated with subsequent sleep duration. Additional models evaluated lagged and cumulative energy intake, and mixed-effects modelling was used for associations between feed energy and time until the next feed. RESULTS: Intake for 24-h infant breast milk was 851.8 ± 194.2 mL and sleep duration was 15.5 ± 3.4 h. The mean energy density of the feeds was 674.7 ± 140.7 kcal/L. Energy intake for the breastfeed preceding a sleep episode was not associated with sleep duration (β = 4.13 min; 95% CI -0.89 to 9.15; p = 0.106). Energy intake from lagged feeds and cumulative energy intake across the three preceding breastfeeds were also not associated with sleep duration (p = 0.171 and p = 0.290 respectively) nor the time until the next breastfeed (β = -0.025; 95% CI -6.2 to 1.4; p = 0.212). CONCLUSIONS: In healthy breastfed infants, the energetic content of breast milk feeds was not associated with subsequent sleep duration or the time until the next feed. These findings suggest that infant sleep-wake behaviour and feeding patterns were not associated with short-term variation in breast milk energy intake. Other factors, including circadian and developmental processes, are likely to contribute to infant sleep behaviour.