The World Health Organization (WHO) recommends exclusive breastfeeding for the first six months of life, as breastfeeding has many proven benefits, including preventing infections and supporting long-term healthy development. However, there is still a common perception among parents and caregivers that breastfed infants sleep less and require more frequent feedings than formula-fed infants. Short sleep duration in infancy is also associated with obesity, behavioral problems, and later cognitive decline. Adequate sleep during this period is therefore considered important for healthy physical and mental development. Although infants are known to sleep longer and more often over time, some caregivers choose to feed with formula due to concerns about their child’s sleep.
To better understand the relationship between infant feeding and sleep, Yuri Nakagawa, a postdoctoral researcher at the University of Toyama in Japan, and colleagues analyzed data from the nationwide Japan Environment and Children’s Survey (JECS), one of the world’s largest birth cohort studies. The study looked at 82,918 mother-infant pairs and investigated whether feeding habits during the first six months of life were associated with sleep duration at one year of age. The survey results are European Journal of Clinical Nutrition March 31, 2026.
”Breastfeeding is widely promoted by the WHO and most people are aware of the many health benefits it provides. Nevertheless, the perception that breastfed infants sleep less or that formula-fed infants sleep more remains common. We wanted to provide hard evidence to dispel this misconception.” said Nakagawa, lead author of the study.
At 6 months of age, mothers were given a questionnaire asking about their breastfeeding habits during the first 6 months for their baby. The children were then divided into four groups according to their feeding method. The first group consisted of infants fed exclusively with formula. The second group included infants younger than 6 months who had been breastfed. The third group included infants who were breastfed for six months while also receiving formula supplementation. The fourth group consisted of infants who were exclusively breastfed for 6 months. When the children reached one year of age, parents completed another questionnaire reporting their children’s sleep duration. Based on the recommendations of the National Sleep Foundation, children who slept less than 11 hours per day were considered to have insufficient sleep.
All breastfed groups were shown to be less likely to be sleep deprived compared to infants who were exclusively formula fed. Infants who were exclusively fed formula for the first 6 months had a 12.2% chance of short sleep duration, whereas infants who were breastfed for less than 6 months had a risk of only 10.2%. If the child was exclusively breastfed for six months and fed formula, the risk was further reduced to 9.7%. Babies who were exclusively breastfed for the first six months had the lowest risk of sleep deprivation at 1 year of age, at 8.8%. After adjusting for a wide range of maternal, infant, and environmental factors, infants who were exclusively breastfed for six months were 23% less likely to sleep less than infants who were exclusively fed formula. The findings also showed a graded association, with longer breastfeeding periods decreasing the likelihood of shorter sleep duration over time.
”This study provides reassurance to the common perception that breastfed babies sleep less because breast milk is digested more quickly.” says Nakagawa.Our findings suggest that such concerns should not prevent parents from considering breastfeeding and its many well-established benefits.” she added.
The researchers proposed several possible explanations. While the nutritional composition of formula is relatively constant, the nutritional composition of breast milk adapts to the changing needs of the infant. To help establish and regulate your baby’s body clock and sleep-wake cycle, melatonin, a hormone that helps you fall asleep and improve sleep quality, is secreted into your breast milk at night. Newborns produce only small amounts of their own melatonin, so melatonin from breast milk may support the development of healthy sleep rhythms. Additionally, breast milk contains tryptophan, an amino acid used in the production of melatonin. Interestingly, tryptophan concentrations in breast milk have been found to be higher at night.
Additionally, there is growing evidence supporting the gut-brain axis, a communication network linking gut bacteria and brain function. Breastfeeding is known to have a positive impact on the development of the gut microbiota in healthy infants. Differences in the gut microbiota between breastfed and formula-fed infants may also contribute to the development of healthy sleep-wake patterns and sleep quality.
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Reference magazines:
Yuya Nakagawa others. (2026). Breastfeeding and children’s sleep duration at 1 year of age: National Birth Cohort – Japanese Environment and Children Survey. European Journal of Clinical Nutrition. DOI: 10.1038/s41430-026-01718-1. https://www.nature.com/articles/s41430-026-01718-1
