A major Japanese study has found that infants who are exclusively breastfed for their first six months sleep longer than their formula-fed counterparts. The research, analyzing data from over 83,000 mother-infant pairs, directly challenges the widespread belief that breastfed babies sleep less.
Lead author Yuri Nakagawa from the University of Toyama stated the goal was to provide solid evidence against this persistent misconception. The findings show a clear gradient: babies exclusively breastfed had an 8.8% risk of short sleep (less than 11 hours daily at age one), compared to 12.2% for those exclusively formula-fed. Even those who received a mix of breast milk and formula showed improved sleep duration.
The biological rationale centers on breast milk's dynamic composition. It contains melatonin and tryptophan, key for regulating sleep-wake cycles, and fosters a gut microbiome linked to better sleep quality. Formula, by contrast, has a constant composition.
Researchers caution that these concerns should not discourage breastfeeding, which the World Health Organization promotes for its many established health benefits. Adequate infant sleep is critical, as short duration has been linked to later health issues.