A researcher collects historical data on a group of subjects and follows them to determine the occurrence of a disease or outcome. Which type of study design does this describe?

Appeared in: NORCET 9 Mains - 2025

Explanation

In a retrospective cohort study, the investigation begins after both the exposure and the outcome have already occurred.
The researcher uses historical records to identify a cohort of individuals based on their past exposure status.
The direction of inquiry is forward, from the past exposure to the subsequent outcome, even though all events are in the past from the researcher's perspective.
This design is efficient for studying outcomes with long latency periods as the time has already passed.

Option A: A prospective cohort study starts in the present with a cohort that is free of the outcome and follows them into the future. The question specifies that the researcher uses 'historical data', which points to a past timeline.
Option C: A case-control study works backward. It starts by identifying individuals who already have the disease (cases) and a comparison group without the disease (controls), and then looks back in time to compare their past exposures. The question describes a forward direction from a cohort to an outcome.
Option D: A cross-sectional study measures both exposure and outcome at a single point in time, providing a 'snapshot' of the population. It does not involve 'following' subjects over any period.

Visual 1: Flowchart - A diagram illustrating the timeline and direction of different study designs. For a retrospective cohort, it would show the researcher standing in the 'present', looking back to define a cohort in the 'past', and then tracing records forward from that past point to a more recent past/present outcome.

Clinical Relevance

Nursing practice connection: Knowing Identification of epidemiological study designs based on methodology helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Understanding study designs is fundamental for evidence-based nursing practice. It allows nurses to critically appraise research articles and determine the strength of evidence for clinical interventions.
Nurses can identify the most reliable studies (like cohort studies for determining risk factors) to inform patient education and care planning.
What if? - If the question stated the researcher identified people with a disease and people without it, and then looked at their past records for exposures, the correct answer would change to 'Case-control study' because the starting point is the outcome, not the exposure.

How to Approach the Question

First, identify the key actions and timing described in the question stem. The crucial phrases are 'collects historical data' and 'follows them'.
Analyze the starting point: 'Historical data' means the study begins by looking at events that already happened in the past.
Analyze the direction of inquiry: 'Follows them to determine the occurrence of a disease' indicates a forward direction, from a cause (exposure) to an effect (outcome).
Combine these two elements: A study that starts in the past and moves forward to an outcome is a retrospective cohort study.
Compare this understanding with the definitions of the options provided to select the best fit.

Concept Tested & Keywords

Concept Tested: Identification of epidemiological study designs based on methodology.
Stem keywords: historical data, follows them, occurrence of a disease, study design
Lead-in keywords: Which type
Negative lead-in flag: false

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