Associations among human milk polyunsaturated fatty acids and infant sleep patterns: a cross-sectional study

Infant sleep is critical for cognitive, emotional, and long-term health outcomes. While diet-sleep relationships are established, limited research has explored how polyunsaturated fatty acids (PUFAs) in human milk (HM) relate to infant sleep. To examine associations between PUFAs in human milk and sleep patterns in 2-month-old infants exclusively fed with HM. This cross-sectional secondary analysis used data from a lactation cookie trial involving 131 parents of healthy, term infants. Participants provided a fasting HM sample and completed sociodemographic and Brief Infant Sleep Questionnaire surveys. Multivariate linear models were adjusted for infant sex assigned at birth, weight-for-length z-scores, maternal pre-pregnancy BMI, and daily feedings. Participants self-identified as 81.7% White, 13.3% Hispanic, with 25.9% reporting an annual income <$45,000 USD. Infants slept an average of 14.67 hours (SD=2.65). PUFAs constituted 20.91% (SD=4.47) of total milk fatty acids, with omega-3 and omega-6 comprising 1.75% (SD=0.53) and 19.16% (SD=4.09), respectively. Significant positive associations were observed between total sleep and omega-3 (B=1.06, SE=0.47, p=.026), omega-6 (B=0.14, SE=0.06, p=.022), alpha-linolenic acid (ALA) (B=1.10, SE=0.53, p=.040), and linoleic acid (LA) (B=0.15, SE=0.06, p=.016). When sleep was partitioned into diurnal or nocturnal, greater omega-3 and omega-6, particularly ALA and LA, were significantly associated with increased diurnal sleep duration: (ALA, B=1.11, SE=0.39, p=.005; LA, B=0.12, SE=0.05, p=.009). No significant associations were observed with nocturnal sleep. Higher HM omega-3 and omega-6 levels, particularly ALA and LA, were associated with greater diurnal sleep in exclusively HM-fed 2-month-olds. Further research is needed to explore underlying mechanisms and long-term developmental impacts. NCT04805008. https://clinicaltrials.gov/study/NCT04805008.