Associations between daily screen time and sleep in a racially and socioeconomically diverse sample of US infants: a prospective cohort study

Abstract

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.

Keywords: paediatrics; public health; sleep medicine.

Figure 1

Predicted, adjusted values of night-time sleep, stratified by infant age, for a range of mean daily screen time (all screen time combined) over the study period; infants were enrolled in a prospective cohort study. Predicted values are the marginal values from a mixed-effects linear regression model adjusted for sociodemographic characteristics (infant age, sex and race; maternal age, marital/cohabitation status and education; and annual household income) and childcare characteristics (hours/week in relative-based or formal childcare, separately). Marital/cohabitation status, annual household income and childcare characteristics were time-varying covariates. Random effects at the infant level and a random slope for age were included in the model. Infant screen time was included as log-transformed and included as two terms to account for the between-infant and within-infant effects. The predicted values in this figure reflect the between-infant differences in night-time sleep for various values of screen time (min/day) among infants, with screen time reflecting the mean daily screen time per day over the study period (ie, the between-infant differences; see table 4, model 4). Data are from 558 dyads with data collected during at least one postpartum follow-up; not all dyads have complete data at each timepoint. The following are the number of infants for each range of average daily screen time over the study period: 0 min/day: n=106; 1–15 min/day: n=66; 16–30 min/day: n=52; 31–45 min/day: n=42; 46–60 min/day: n=39; 61–75 min/day: n=25; 76–90 min/day: n=30; 91–105 min/day: n=22; 106–120 min/day: n=19; 120+ min/day: n=157.

Figure 2

Predicted, adjusted mean values of (A) night-time, (B) daytime and (C) 24-hour sleep at 12 months of age, by average daily television (TV)+DVD screen time over the study period. Values are adjusted for other infant screen time. Predicted values are the marginal values from separate mixed-effects linear regression model (n=555) adjusted for sociodemographic characteristics (infant age, sex and race; maternal age, marital/cohabitation status and education; and annual household income) and childcare characteristics (hours/week in relative-based or formal childcare, separately). Marital/cohabitation status, annual household income and childcare characteristics were time-varying covariates. Random effects at the infant level and a random slope for age were included in the model. TV+DVD time was included as a log-transformed variable in the regression model and was included as two terms to account for the between-infant and within-infant effects; each model was also adjusted for all other (ie, non-TV+DVD) screen time. The predicted values in this figure reflect the mean values for each sleep outcome for various values of TV+DVD screen time (min/day), with TV+DVD screen time being the average over the entire 1-year study period (ie, between-infant effects). Data are from 558 dyads with data collected during at least one postpartum follow-up; not all dyads have complete data at each timepoint. The following are the number of infants per each range of average daily TV+DVD time over the study period: 0 min/day: n=124; 1–15 min/day: n=82; 16–30 min/day: n=52; 31–45 min/day: n=47; 46–60 min/day: n=50; 61–75 min/day: n=26; 76–90 min/day: n=24; 91–105 min/day: n=22; 106–120 min/day: n=12; 120+ min/day: n=119.