Infant Temperament, Breastfeeding, and Sleep at 6 and 14 Months

Background/Objectives: Sufficient sleep quantity/quality in infancy is crucial for healthy development, so it is important to identify early associated predictive factors. Research findings highlight salient endogenous (infant temperament) and exogenous (breastfeeding) influences, though no known studies have examined nuanced and interactive relations among these variables from early to late infancy/toddlerhood. Thus, the current study examined the main and interaction effects of these variables on infant sleep at 6 and 14 months while controlling for prenatal cortisol exposure. Methods: Data from a subsample (n = 79) of the Infant Development and Healthy Outcomes in Mothers Study were used, including prenatal maternal saliva samples assayed for cortisol and maternal questionnaires that included retrospective reporting of infant temperament, sleep quality and quantity, and breastfeeding frequency. Results: Multiple linear regression results include a statistically significant negative relation between prenatal maternal cortisol area under the curve and 6-month infant sleep quantity. A greater breastfeeding frequency at 6 months was associated with decreased 6-month sleep quality via conditional but not interaction effects. Greater 6-month infant Surgency was associated with better sleep quality at 14 months. There were no statistically significant interaction effects. Conclusions: The findings suggest that maternal psychophysiological stress has a significant influence on infant sleep duration, while research should further investigate the role of infant temperament and breastfeeding in shaping infant sleep quality. Significant conditional effects highlight patterns that should be re-examined with a larger sample to determine whether infant temperament may buffer against negative associations between breastfeeding frequency and infant sleep quality in early and late infancy in a developmental stage-consistent manner. Future replication studies should include a multi-method, longitudinal assessment of all key study variables, as well as a larger, more sociodemographically diverse sample of maternal-infant dyads.