More screen time cuts exercise, sleep time in teens

Most children and adolescents use multiple screens at the same time, according to a recent study. In addition, any degree of screen time, rather than the number of screens in concurrent use, is a strong deterrent to physical activity, reduces sleep time, and increases body mass index (BMI).

“Just using a screen is the issue here rather than the fact there are multiple screens used at once,” the researchers said. “For example, a participant using any number of screens at the weekend would have approximately 20 minutes lower moderate-to-vigorous physical activity (MVPA) per day and approximately 8-mg lower mean acceleration per day than a participant using no screens at the weekend.”

A total of 816 adolescent girls (mean age, 12.8±0.8 years) participated in the study and were made to wear an accelerometer for 7 days for the measurement of sleep and physical activity. Screen use, as well as other psychosocial variables, were obtained from self-reports.

Fifty-nine percent of the participants reported using ≥2 screens at the same time after school. This percentage increased to 65 percent in the evening and to 68 percent during weekends. Right before bed, only 36 percent still reported concurrent screen use. [Acta Paediatr 2021;doi:10.1111/apa.15806]

Mobile/smartphones were the most common devices, which 94.3 percent of the adolescents either owned or had access to. This was followed by tablets (77.3 percent) and laptops (71.4 percent).

Screen time of any degree was associated with lowered physical activity. For example, participants who reported one screen during the weekend engaged in 18.4 minutes less daily MVPA than counterparts who had no screen use.

Concurrent use of an increasing number of screens slightly strengthened the effect. Those who used two, three, and ≥4 screens during the weekend saw an MVPA drop of 19.7, 22.1, and 20.9 minutes per day, respectively.

A similar impact on overall PA was observed, with the use one, two, three, and ≥4 screens decreasing PA by 7.57, 8.03, 8.82, and 8.53 mg, respectively. At the same time, weekend use of ≥2 screens was also significantly associated with higher sedentary time.

In turn, screen use correlated with BMI. Those who reported one screen use after school had BMI higher by 0.80 kg/m² than adolescents with no such screen use. Increasing the number of screens in concurrent use to two, three, and ≥4 corresponded to 0.73-, 0.73-, and 0.86-kg/m² increases in BMI.

Screen use also negatively affected adolescent sleep. Adolescents who used one, two, and three screens after school reported sleeping for 0.44, 0.54, and 0.68 hours less on weekdays, respectively.

“We hypothesized that more screens used concurrently would be associated with less favourable levels of psychosocial measures,” the researchers noted. However, “[o]ther than those using four or more screens in bed having lower self-esteem scores, we did not find any associations with self-worth, self-rated body attractiveness, or health-related quality of life.”

“Concurrent screen use may pose an opportunity to target young people with interventions or health-related content through multiple devices. This study adds to the evidence base to inform future screen use guidelines,” they added.