Screen time in kids, teens tied to cardiometabolic and cardiovascular risks

A study using data from two Danish cohorts demonstrates an association between cardiometabolic risk (CMR) and cardiovascular risk (CVR) and screen time (ST) in children and adolescents, be it through phone, television, or gaming.

In this digital age, most people are constantly glued to their screens, the researchers noted. “[Our study shows that] ST was positively associated with CMR and CVR … Sleep duration moderated these associations – shorter sleep amplifies the relationship between ST and CMR in both children and adolescents.”

The investigators evaluated data from participants in the COPSAC*2010 and COPSAC2000 mother-child cohorts. COPSAC2010 included 700 mother-child pairs, while COPSAC2000 comprised 411 children born to mums with asthma. Extensive phenotyping from clinical visits and exposure assessments was conducted from birth up to ages 10 (COPSAC2010) and 18 (COPSAC2000) years. [J Am Heart Assoc 2025;14:e041486]

COPSAC2010: Associations in children

In this cohort, ST was available for 657 kids at age 6 years and 630 kids at age 10 years. Average STs were 2 and 3.2 h at ages 6 and 10 years, respectively, indicating a significant increase over time (p<0.001).

A significant positive association was observed between each additional hour of ST and CMR (0.08; p=0.021) after adjusting for relevant confounders. The association was directionally stronger in boys (0.10; p=0.013) vs girls (0.02; p=0.694), and at age 10 (0.16; p=0.007) vs age 6 years (0.06; p=0.321).

Moreover, each additional hour of ST from age 6 to 10 years was tied to an increase in HOMA-IR** (0.03; p=0.006). In adjusted models, ST showed a positive trend with the NMR*** CVR score at age 10 years (0.06; p=0.15).

COPSAC2000: Associations in adolescents

In COPSAC2000, ST was available for 364 adolescents. Average ST at age 18 years was 6.1 h (p<0.001).

There was also a significant positive association between ST and CMR factors at age 18 years (0.13; p<0.001). The CMR factors include waist circumference (WC; 1.30; p<0.001), systolic blood pressure (SBP; 0.63; p=0.011), HDL-C^# (-0.01; p=0.032), glycoprotein acetyls (0.01; p<0.001), and apolipoprotein B (0.01; p=0.001).

In the sex-stratified analysis, there were stronger associations in boys for CMR (0.14; p=0.001), WC (1.56; p<0.001), and SBP (0.9; p=0.008).

At age 18 years, ST was also associated with increased BMI in girls (0.37; p=0.039) and all^## measured body anthropometrics in boys (p≤0.015), as well as with the NMR CVD score in adjusted models (0.07; p=0.017).

Sleep a mediating factor

In COPSAC2010, there were significant effect moderations between ST and sleep duration (p=0.029), and between ST and sleep onset time (p=0.009).

In COPSAC2000, there was a significant moderation between ST and sleep duration on total CMR (p=0.012) and a directional but nonsignificant interaction between ST and sleep onset time (p=0.22).

According to the researchers, these findings suggest that the positive association between ST and CMR increased as the amount of sleep decreased, and that later sleep onset may worsen the detrimental effects of ST on CMR.

The link between sleep duration and CMR in childhood and adolescence may have been driven by circadian rhythm misalignment, sodium retention secondary to insulin resistance, and increased sympathetic nervous system activity. [Curr Hypertens Rep 2020;22:19; Sleep Med Rev 2016;29:76-100; JAMA Pediatr 2016;170:487-494] Evidence shows that evening screen may disrupt circadian rhythms, delay melatonin production, and decrease sleep duration. [Sleep Med Rev 2015;21:50-58]

“These potential mechanisms may contribute to hormonal dysregulation, increased appetite, and weight gain in children and adolescents,” said the researchers.

On sex-stratified analyses, the interaction between ST and sleep duration was more pronounced among boys in COPSAC2010 (p=0.031), while that between ST and sleep onset time was significant among girls in COPSAC2000 (p=0.005). “[The latter finding implies] that the detrimental moderation on CMR of increased ST is magnified when sleep onset is later in female adolescents,” the researchers explained.

Actionable targets

The results underscore the consistent association between ST and elevated CMR, with sleep duration and time of onset acting as potential contextual factors, the investigators said. “Although our observed effect sizes may appear modest, these reflect consistent shifts across multiple CM domains per additional hour of ST and may indicate early divergence in CM health trajectories.”

“Our findings may suggest actionable targets. For instance, in childhood, where sleep onset time and total sleep duration were closely linked, encouraging earlier bedtimes may increase overall sleep time and thus potentially mitigate adverse CMR factors associated with ST in childhood,” they explained.

Interventions focused on restricting screen exposure pre-bedtime and promoting sleep hygiene practices may help mitigate the potential metabolic impact of ST in vulnerable young individuals. The investigators added that sleep quality may also factor in metabolic health and could thus be an important target for future interventions.

“By juxtaposing the two independent mother-child cohorts … we gain valuable insights into how ST patterns and their potential impact on CMR evolve from childhood through adolescence,” said the researchers. “The findings highlight the importance of jointly considering ST and sleep patterns in the assessment of early-life risk factors for CM and CV health.”