Type-specific screen time associations with cardiovascular risk markers in children

Background: There is evidence that TV time may have stronger associations with cardiovascular risk markers than other types of screen time, but most studies focus on TV, or total screen time.

Purpose: To examine associations between types of screen time and cardiovascular risk markers in school-age children.

Methods: Cross-sectional study of 2515 school children in Portugal (aged 2-12 years, data collected in 2009 and 2010). Three types of screen time (TV, electronic games, and PC time) were collected through a questionnaire, and data on three cardiovascular risk markers (resting heart rate; diastolic blood pressure [DBP]; and systolic blood pressure [SBP]) were collected by a trained fieldworker. Complex-samples generalized linear models were run for each combination of screen time predictor and cardiovascular risk outcome, and a clustered cardiovascular risk score, adjusting for potential confounders (including physical activity). Analyses were conducted in 2011 and 2012.

Results: TV viewing, but not PC or electronic games time, was associated positively with clustered cardiovascular risk score, DBP, and SBP after adjustment for all covariates. Watching TV for >2 hours/day (compared to <1 hour/day) was associated with higher DBP (coefficient, logged and back-transformed 0.02, 95% CI=0.00, 0.04, linear trend p=0.003); SBP (logged and back-transformed 0.02, 95% CI= -0.01, 0.05, p=0.009), and clustered cardiovascular risk score (0.13, 95% CI=0.02, 0.24, p<0.001).

Conclusions: TV viewing, but no other type of screen time, was associated positively with cardiovascular risk markers independently of physical activity. Studies using a single marker of screen time or sedentary behavior may conceal screen time type-specific associations.