Socioeconomic status and infant nighttime sleep across the second year of life: The moderating role of infant attachment security

This study examined socioeconomic status (SES) and attachment security as predictors of infant nighttime sleep during the second year. Participants included 128 mothers (86% White) with infants (48.4% boys). Data collection took place between April, 2009 and February, 2014. At 12, 18, and 24 months, infant sleep was assessed via actigraphy and daily diaries, and attachment with the Attachment Q-Set. SES indicators included income-to-needs ratios and education. Lower SES predicted greater variability in sleep duration and later sleep timing only for less secure infants. Less secure attachment was associated with poorer sleep at both between- and within-person levels, especially when infants were 12 months of age. Results emphasize the complex interactive effects of environmental and relational factors on infant sleep.