What type of study design is represented by a research project that follows football players with and without concussions over time to compare their brain concussion symptoms and neuropsychologic test results?

Study Design Analysis: Wisconsin Football Player Concussion Study

The study described represents a cohort study design, where football players were followed over time to assess concussion outcomes.

Characteristics of This Cohort Study

This research exhibits the classic elements of a cohort study design:

• Defined cohort: 500 football players at 13 high schools in Wisconsin
• Baseline assessment: All subjects underwent preseason standardized testing for brain concussion symptoms and neuropsychologic evaluation
• Follow-up period: Subjects were followed during the football season
• Outcome measurement: 13 players who suffered concussions were assessed with repeat testing
• Comparison group: Results were compared to 6 uninjured players from the same teams

Key Features Supporting Cohort Classification

1. Temporal sequence: The study follows the classic cohort design pattern where subjects are first identified, then followed forward in time to observe outcomes 1

2. Exposure-to-outcome direction: The research tracks from baseline characteristics to subsequent concussion outcomes 2

3. Prospective data collection: The study collected baseline data before injuries occurred and then followed participants to observe who developed concussions 2, 1

4. Comparison of outcomes: The study compares outcomes between those who experienced concussions and those who did not 1

Why This Is Not Other Study Types

• Not a case-control study: Case-control studies work backward from outcome to exposure. This study identified subjects first and then followed them to see who developed concussions 1

• Not a cross-sectional study: Cross-sectional studies measure exposure and outcome at the same time point. This study has distinct time points (preseason baseline and post-injury) 2

• Not a randomized controlled trial: There was no intervention being tested or random assignment to groups 2

• Not a randomized crossover trial: There was no intervention that subjects crossed over to receive 2

Significance in Concussion Research

This cohort design is particularly appropriate for studying concussions in sports, as it allows researchers to:

1. Calculate the incidence of concussions in the population (13 out of 500 players)

2. Compare neuropsychological changes before and after injury

3. Evaluate recovery patterns by conducting multiple post-injury assessments 3

4. Identify potential risk factors for concussion or prolonged recovery 4

Similar cohort designs have been used in larger studies like the NCAA-DoD CARE Consortium, which has helped identify risk factors for persisting post-concussion symptoms 4, 5.

Methodological Considerations

• Control selection: The small number of controls (6 uninjured players) compared to cases (13 concussed players) could introduce bias

• Follow-up completeness: The study would need to ensure all concussions were captured during the season

• Confounding factors: Factors like position played, prior concussion history, and neck strength would ideally be measured and controlled for 6

Cohort studies like this one provide valuable information about the natural history of concussions and can help identify biomarkers associated with injury and recovery 6.