A study conducted among 300 people 100 who are affected by lung cancer and 200 who are smokers not affected by lung cancer, what type of study design is represented here?

Appeared in: NORCET 3 - 2022 (Shift-2)

Explanation

A case-control study is an observational design that starts by identifying individuals with a specific outcome (cases) and a group without that outcome (controls).
It then looks backward in time (retrospectively) to compare the frequency of past exposure to a potential risk factor between the two groups.
In this scenario, the 'cases' are the 100 people with lung cancer, and the 'controls' are the 200 people without lung cancer.
The study's goal is to compare the history of smoking (the exposure) between these two groups to find a statistical association.

Option A: A cohort study starts by identifying groups based on their exposure status (e.g., smokers and non-smokers) and follows them forward in time to observe who develops the disease. The study in the question starts with the disease, not the exposure.
Option B: A field trial is an experimental study, not an observational one. It involves applying a preventive intervention (like a vaccine) to healthy individuals in a community setting to see if it reduces the incidence of a disease.
Option D: A cross-sectional study measures both exposure and disease at a single point in time, providing a 'snapshot' of the population. It is used to determine prevalence. The study described here has a clear temporal direction (looking back from disease to cause).

Visual 1: Flowchart: A diagram comparing the structure of a case-control study (starts with Disease -> looks back to Exposure) versus a cohort study (starts with Exposure -> looks forward to Disease). This visual helps clarify the fundamental difference in directionality.
Visual 2: Infographic: An infographic summarizing the key features, advantages (e.g., good for rare diseases, quick, inexpensive), and disadvantages (e.g., recall bias, selection bias) of case-control studies.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Epidemiological Study Designs as background academic context rather than a clinical decision trigger.
Understanding study designs is crucial for nurses to practice evidence-based care. It allows them to critically appraise research articles and determine the validity and applicability of findings to their patients.
Case-control studies are highly efficient for investigating risk factors for rare diseases or diseases with a long latency period (like many cancers), which would be impractical to study with a cohort design.
Nurses often participate in research by helping to identify 'cases' (patients with a specific condition) from hospital records for such studies.

How to Approach the Question

First, identify the core components of the study described in the question: Who are the subjects and what is being measured?
Determine the starting point of the investigation. Does the study begin with people who already have the disease (outcome) or with people who have a specific behavior (exposure)?
In this question, the study starts by identifying people 'affected by lung cancer' (the outcome). This is the key clue.
Recall the definitions of the main observational study designs: Case-control starts with the outcome and looks back; Cohort starts with the exposure and looks forward; Cross-sectional measures both at the same time.
Since this study starts with the disease (cases) and compares them to those without the disease (controls) to look for a past cause, it matches the definition of a case-control study.

Concept Tested & Keywords

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Practise the full NORCET 3 - 2022 (Shift-2)

Attempt every question from this paper in a timed mock, then review the full solution for each one.