Screen time, physical activity affect sleep in teens

Among adolescents, less screen time and more physical activity may help promote more stable sleep, a recent study has found.

Wrist accelerometers were given to 247 teenagers (mean age, 15.8±0.3 years; 144 girls) to measure their sleep and activity patterns over 1 week. Screen time was self-reported through a seven-point Likert scale. At baseline, the mean body mass index (BMI) and body fat percentage were 21.9±3.0 kg/m² and 25.0 percent, respectively.

Participants logged an average of 2,043±471 cpm/day of physical activity, which tended to be higher during school days. The average screen time was 5.6±2.3 hours per day and was higher during non-school days, such as weekends or holidays. Girls tended to have lower overall screen time and higher levels of physical activity than boys.

Screen time had a significantly negative impact on sleep, leading to later bedtime (p=0.03) and shorter rest (p=0.02) and sleep (p=0.047) durations. Each additional hour of screen time pushed bedtime back by 0.12 minutes and cut rest and sleep duration by 2.8 and 2.2 minutes, respectively.

Physical activity likewise reduced sleep and rest durations (p<0.0001 for both) and was linked to an earlier rise time (p=0.0003), while simultaneously decreasing awakenings during the night (p=0.0002).

Adjusted linear regression analysis further showed that screen time was significantly related to night-to-night variations in sleep parameters, particularly total sleep (p=0.001) and rest (p=0.001) time, bedtime (p<0.001), and rise time (p=0.03). Analysis according to sex found that all of these were driven by boys and none of the interactions were significant in girls.

Physical activity also correlated with sleep variability in terms of number of awakenings (p<0.001) and rise time (p=0.013), with such interactions observed in both boys and girls.