Relations between infant sleep quality, physiological reactivity, and emotional reactivity to stress at 3 and 6 months.

The study examines the association between infant sleep, physiological, and emotional reactivity at 3 and 6 months of age in 89 African American infants and their caregivers. Infant sleep was objectively measured at 3 and 6months using actigraphy for 7 days and nights. At 6 months of age, dyads participated in the Still-Face Paradigm (SFP) (Tronick et al., 1978) to assess infants' physiological reactivity (via respiratory sinus arrhythmia (RSA)) and emotional reactivity. Findings revealed that infant night wakings at 3 months was positively correlated with baseline RSA at 6 months (β = .35, p < .001). Night wakings at 3 months marginally predicted negative affect during the recovery episode of SFP (β = -.26, p = .057). Further, night wakings at 6-months-old predicted more positive affect during the recovery episode of SFP (β = .34, p = .007). We discuss potential explanations for these findings such as an exuberant temperament style, parenting behavior, and lack of sleep consolidation at this early age to be the focus of future studies in this area. The current study adds to the limited research examining the relationship between sleep and reactivity in the earliest months of development. Findings reveal that it is critical to take developmental timing into account as all results were unexpected in relation to the childhood literature. Moreover, this is the first study of its kind to focus on an African American sample.