Question

a hypothetical cohort study was undertaken among 600 adhd - free children in south carolina. the purpose of the study was to examine the effects of increased screen time during childhood on the subsequent diagnosis of adhd by young adulthood. the childrens screen time was assessed by a questionnaire, and the children were followed for 10 years. the following data were obtained from the study.
what is the distinguishing feature of a cohort study design such as this? (1 point)
(a) exposure status is assessed, and then the participants are followed up over time to see who develops the outcome.
(b) exposure and outcome are measured at the same time, so temporality cannot be established.
(c) the investigator randomizes participants into exposure groups and then follows them to see who develops the outcome.
(d) participants are selected based on disease status, and then exposure status is assessed from the past.

Explanation:

In a cohort study, researchers first assess the exposure status (here, screen - time) of participants (ADHD - free children). Then, they follow these participants over time (10 years in this case) to observe the development of the outcome (ADHD diagnosis).

• Option B describes a cross - sectional study where exposure and outcome are measured simultaneously.
• Option C describes a randomized controlled trial.
• Option D describes a case - control study.

Answer:

A. Exposure status is assessed, and then the participants are followed up over time to see who develops the outcome.