| Summary: | Objective To determine the associations between screen media use and sleep throughout infancy (3–12 months).Design Prospective Nurture birth cohort.Setting North Carolina, USA, 2013–2015.Participants Women enrolled in their second to third trimester, completed a phone interview after birth, and completed home visits at 3, 6, 9 and 12 months post partum.Primary and secondary outcome measures Women reported the usual hours their infants slept during the day and night and their infants’ usual use of five screen media activities at 3, 6, 9 and 12 months post partum. Adjusted mixed-effects regression analyses modelled the associations between infant screen time and sleep outcomes while disaggregating the between-infant and within-infant effects.Results Among 558 mother–infant dyads, 374 (67.0%) infants were black and 304 (54.5%) households earned <$20 000 per year. Half (254, 50.2%) of the infants engaged with screens at 3 months of age, while 326 (72.9%) engaged at 12 months. The median value of the average daily screen time over the study period was 50 (IQR: 10–141) min. Infant screen time was inversely associated with night-time sleep duration only when considering between-infant effects (adjusted beta: −2.9; 95% CI −5.9 to 0.0; p=0.054 for log-transformed screen time). Effects were stronger for television+DVD viewing specifically (adjusted beta: −5.2; 95% CI −9.1 to −1.4; p<0.01 for log-transformed television+DVD time). For example, an infant who averaged 1 hour of television+DVD viewing over the study period slept, on average, 9.20 (95% CI 9.02 to 9.37) hours per night by 12 months compared with 9.60 (95% CI 9.41 to 9.80) hours per night for an infant with no screen time over the study period. There were no significant within-infant effects between screen time and night-time sleep, and screen time was not associated with daytime sleep or night-time awakenings.Conclusions Screen time during infancy was inversely associated with night-time sleep duration; however, causal associations remain uncertain.Trial registration number NCT01788644.
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