All of the following are the features of cohort studies, EXCEPT:

DSSSB 6 September 2024

Nursing Research & Statistics

Easy

Appeared in: DSSSB 6 September 2024

Explanation

This statement describes a study where both the exposure and the outcome have already happened before the investigation begins.
This is the defining characteristic of a case-control study, which starts with individuals who have the disease (cases) and looks backward in time to find the exposure.
In a standard prospective cohort study, the outcome has not yet occurred at the start of the study; the group is followed forward in time to observe who develops the outcome.

Option A: This is a core feature of a cohort study. These studies are longitudinal, meaning they follow groups over a period to measure the incidence (new cases) of a disease.
Option B: This is the fundamental principle of a cohort study. The design is intended to move forward, from a potential cause (exposure) to a future effect (outcome/disease).
Option C: This is the correct starting point for a cohort study. The investigation begins by selecting a group of individuals who are free of the disease being studied and then classifies them based on their exposure status.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Epidemiological Study Designs: Cohort vs. Case-Control as background academic context rather than a clinical decision trigger.
Understanding different study designs is crucial for nurses to critically appraise research and apply evidence-based practice. Cohort studies provide stronger evidence for causation than case-control studies.
Nurses in public health and research roles often participate in data collection and patient follow-up for cohort studies.
What if? If a nurse wanted to study a very rare disease, a case-control study would be a more efficient and less expensive design. It would be difficult and costly to follow a large cohort for a long time just to observe a few cases of a rare outcome.

How to Approach the Question

First, identify the core concept of the question, which is 'cohort studies'.
Second, recognize the negative keyword 'EXCEPT'. This means you are looking for the one option that is FALSE or does not apply to cohort studies.
Third, recall the key features of a cohort study: it is typically prospective (forward-looking), starts with a disease-free population grouped by exposure, and follows them over time to see who develops the disease (cause to effect).
Fourth, evaluate each option against this definition.
Options A, B, and C all correctly describe fundamental aspects of a cohort study.
Option D describes a study where everything has already happened, which is the classic design of a case-control study (effect to cause). This makes it the correct exception.

Concept Tested & Keywords

Concept Tested: Epidemiological Study Designs: Cohort vs. Case-Control
Stem keywords: cohort studies, features
Lead-in keywords: EXCEPT
Negative lead-in flag: The question asks to identify the statement that is NOT a feature of a cohort study.

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E6 Parks TextBook of Preventive & Social Medicine part 1 — Subpart A (pp 26-201 of 604) pp. 72-74, 68-70