Too much screen time in early childhood a harbinger of unhealthy lifestyle behaviour later in life

Toddlers with a longer screen viewing time were more sedentary and spent less time engaged in physical activity later in life at age 5.5 years, according to the Growing Up in Singapore Towards healthy Outcomes (GUSTO) study — supporting the hypothesis that screen viewing may have a negative influence on health by displacing physical activity.

“The findings suggest that interventions to remove or restrict screen access during early childhood might prevent the displacement of health-enhancing physical activity by sedentary behaviour during the subsequent years,” wrote Dr Dorothea Dumuid from the University of South Australia in Adelaide, Australia in a linked commentary. [Lancet Child Adolesc Health 2020;doi:10.1016/S2352-4642(20)30005-5]

“Early childhood might be a crucial intervention window for preventing future unhealthy behavioural trajectories.”

The current analysis involved 552 children in Singapore whose mothers were enrolled in the ongoing longitudinal birth cohort GUSTO study. Parents reported on their child’s screen viewing time during age 2–3 years and the children’s movement behaviours were recorded over 7 consecutive days using wrist-worn accelerometers at age 5.5 years. Movement behaviours refer to sedentary behaviour, physical activity, and sleep that represent the movement spectrum over 24 hours. [Lancet Child Adolesc Health 2020;doi:10.1016/S2352-4642(19)30424-9]

Total screen viewing time at early life was negatively associated with both light (p<0.0001) and moderate-to-vigorous physical activity (MVPA; p<0.0001) as well as sleep (p=0.008) at age 5.5 years, in relation to sedentary behaviour.

Compared with a total screen time of <1 hour/day, spending ≥3 hours/day on the screen was associated with more time engaged in sedentary behaviour (480.0 vs 439.8 minutes/day) and less time on light physical activity (356.2 vs 384.6 minutes/day) and MVPA (63.4 vs 76.2 minutes per day) at age 5.5 years.

“[We] found a dose-response relationship whereby estimated daily time spent engaging in light physical activity and MVPA decreased while sedentary behaviour time increased. These findings suggest that even small amounts of daily screen viewing could have negative effects on health behaviours,” observed the researchers led by Dr Falk Müller-Riemenschneider from Saw Swee Hock School of Public Health, National University of Singapore, Singapore.

When the analyses were stratified by the type of device, the trends were similar be it for television viewing or handheld device viewing.

There were no significant differences in the sleep duration of those with ≥3 hours/day vs <1 hour/day of screen time (540.4 vs 539.5 minutes/day). 

“Our findings indicate that screen viewing might displace physical activity during early childhood, and suggest that reducing screen viewing time in early childhood might promote healthier behaviours and associated outcomes later in life,” the researchers concluded.

According to recommendations by the WHO, screen time of children aged 2–5 years should be limited to 1 hour per day or less. 

“In the present study, children spent on average more than 2 hours/day watching screen devices at 2–3 years, and only a small proportion of children met [the] WHO recommendations,” noted Müller-Riemenschneider and co-authors.

“Considering the substantial amount of screen viewing time at ages 2–3 years and its negative impact on movement behaviours and health later in life, strategies to reduce screen viewing time during the early years are needed to address this important public health threat,” they added.