Study Design Classification
This is a cohort study (Answer A). The scenario describes two groups of children being followed based on their exposure status (TV watching vs. no TV watching) to assess potential health outcomes over time, which is the hallmark of a cohort study design 1.
Key Features That Define This as a Cohort Study
Exposure-based grouping: Children are divided into groups based on their exposure status (2 hours daily TV viewing vs. no TV viewing) at the start of the study 1.
Prospective follow-up: The design implies following these groups forward in time to observe outcomes, which is characteristic of cohort methodology 1.
Temporal sequence: Exposure (TV watching) precedes outcome measurement, allowing for assessment of causal relationships between screen time and health outcomes such as BMI changes, psychological difficulties, and developmental outcomes 2, 3, 4.
Why Other Study Designs Don't Fit
Not case-control (B): A case-control study would start with children who already have an outcome (e.g., obesity) and look backward to assess TV exposure history 1.
Not cross-sectional (C): Cross-sectional studies measure exposure and outcome simultaneously at a single time point, without follow-up 1.
Not randomized controlled trial (D): There is no mention of random assignment to TV watching groups. The children are simply observed based on their existing TV viewing patterns 1.
Clinical Context
This cohort design is commonly used in pediatric screen time research to evaluate associations between TV viewing and outcomes like overweight status, BMI trajectory, and psychological difficulties 2, 3, 4. Studies using this methodology have demonstrated that children watching ≥2 hours of TV daily have 1.48-1.52 times higher odds of being overweight compared to those watching none 2, and that early viewing patterns established in infancy persist into school age 5.