Abstract
BACKGROUND AND OBJECTIVES: The Intervention Nurses Start Infants Growing on Healthy Trajectories (INSIGHT) responsive parenting (RP) intervention for first-time mothers improved firstborn infant sleep compared with controls. The goals of this analysis were to test intervention spillover effects on secondborn siblings and examine birth order differences in infant sleep. METHODS: Secondborns (n = 117) of INSIGHT mothers were enrolled in an observational cohort, SIBSIGHT. The Brief Infant Sleep Questionnaire was collected at 3, 16, and 52 weeks. Generalized linear mixed models assessed differences among secondborns by firstborn randomization, as well as birth order differences at 16 and 52 weeks. RESULTS: The RP group secondborns slept 42 minutes longer at night (95% confidence interval [95% CI]: 19-64) and 53 minutes longer total (95% CI: 17-90) than control secondborns. RP secondborns were more likely to self-soothe to sleep (odds ratio [OR] = 2.0, 95% CI: 1.1-3.7) and less likely to be fed back to sleep after waking (OR = 0.5, 95% CI: 0.3-0.9) than secondborns of control mothers. RP secondborns were more likely to have a bedtime ≤8 pm at 3 (OR = 2.9, 95% CI: 1.1-7.7) and 16 weeks (OR = 4.7, 95% CI: 2.0-11.0). Few differences in sleep parenting practices were observed when comparing siblings within families. Secondborns slept 37 minutes longer than firstborns at 16 weeks (CI: 7-67, P = .03). CONCLUSIONS: The INSIGHT RP intervention for first-time mothers had a spillover effect to secondborns, positively impacting sleep duration and behaviors. Intervening with first-time mothers benefits both firstborns and subsequent children.