A research group including Graduate Student Yuri Nakagawa of the Medical Life Sciences Program of Graduate School of Medicine and Pharmaceutical Sciences at the University of Toyama, and Professor Emeritus Hidekuni Inadera of the Toyama Regional Center for Japan Environment and Children's Study (JECS), University of Toyama, has revealed that children who were breastfed up to 6 months of age tend to be less prone to sleep deprivation at 1 year of age compared to those raised exclusively on infant formula. The finding was made by investigating the association between infant nutrition methods and sleep duration at age 1 using data from JECS. The result scientifically backs the importance of breastfeeding and was published in the European Journal of Clinical Nutrition on March 31.
Provided by the University of Toyama
Short sleep duration during infancy has been reported to be associated with future obesity, behavioral issues, and diminished learning capabilities. Securing sufficient sleep during this period is considered crucial for subsequent physical and mental development.
Breastmilk is known to offer various benefits, including the prevention of infectious diseases and positive impacts on long-term health. The World Health Organization (WHO) also recommends exclusive breastfeeding for the first 6 months of life. However, the connection between infant nutrition methods and subsequent sleep remained poorly understood.
Therefore, the research group examined the association between infant nutrition methods (combinations of breastmilk and formula, and their durations) and sleep duration at 1 year of age. Targeting 82,918 children participating in JECS, the researchers categorized nutrition methods up to 6 months after birth into four groups (exclusive formula feeding for 6 months, breastfeeding for less than 6 months, breastfeeding for 6 months + formula, and exclusive breastfeeding for 6 months). Sleep duration at age 1 was calculated based on parental responses, with less than 11 hours defined as sleep deprivation.
Multiple logistic regression analysis was utilized for the evaluation of the aforementioned association, adjusting for maternal age, socioeconomic status, and other confounding factors.
The results revealed that, compared to the exclusive formula feeding group, children raised exclusively on breastmilk had the lowest risk of sleep deprivation at 0.77 times. The group with breastfeeding for 6 months + formula stood at 0.79 times, and the group with breastfeeding for less than 6 months stood at 0.84 times.
Components contained in breastmilk, such as melatonin and tryptophan, along with differences in gut microbiota, may be influencing these outcomes. Melatonin is a hormone involved in regulating the body's internal clock and is thought to improve sleep quality and facilitate falling asleep. Tryptophan is a precursor to melatonin whose concentration increases at night. These components potentially participate in the development of an infant's circadian rhythm.
Newborns cannot secrete sufficient melatonin on their own for some time after birth. Furthermore, because the formation process of gut microbiota differs between breastfeeding and formula feeding, gut bacteria could also be involved in neurological development and sleep regulation.
Moving forward, the team notes the need to track how this connects to long-term development and clarify the underlying mechanism in greater detail.
Inadera stated: "We conducted this study because it had been reported that infant nutrition methods might relate to the formation of sleep rhythms. Since the WHO recommends exclusive breastfeeding for up to 6 months of age, we investigated the association between nutritional status up to 6 months after birth and sleep at the 1-year mark. In the future, we plan to examine longer-term impacts, such as from ages 2 to 3 and beyond. Within this cohort, the group with exclusive breastfeeding up to 6 months accounted for 35.9%, exclusive formula feeding for 2.7%, and the remainder fell into the mixed feeding group. Because some mothers face difficulties continuing breastfeeding due to various reasons, we believe a stance of continuing breastfeeding as much as possible is appropriate."
Journal Information
Publication: European Journal of Clinical Nutrition
Title: Breastfeeding and children's sleep duration at 1 year of age: A nationwide birth cohort - The Japan Environment and Children's Study
DOI: 10.1038/s41430-026-01718-1
This article has been translated by JST with permission from The Science News Ltd. (https://sci-news.co.jp/). Unauthorized reproduction of the article and photographs is prohibited.