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Difficulty: MediumStudy Design

An occupational medicine physician working for a national labor union is evaluating the long-term health impacts of a specific synthetic resin used at a single large aerospace manufacturing plant. The resin was utilized continuously from 2000 to 2015 before being phased out. The physician aims to determine if there is an association between handling this resin and the subsequent development of interstitial lung disease.

Using the plant's archived human resources logs, the physician categorizes 800 former employees based on whether their daily job duties involved direct contact with the resin. The physician then cross-references these two groups with state health registries from 2000 to 2026 to calculate and compare the incidence of interstitial lung disease between the exposed and unexposed workers.

Which of the following best describes the design of this investigation?

  1. Retrospective cohort studyAnswer
  2. B
    Case-control study
  3. C
    Prospective cohort study
  4. D
    Cross-sectional study
  5. E
    Ecological study

Answer

Retrospective cohort study
The correct answer is a retrospective cohort study. In this epidemiological design, the investigator establishes the study groups based on historical exposure status (in this scenario, handling the synthetic resin versus not handling it) using archived records. The investigator then evaluates the subsequent incidence of the outcome (interstitial lung disease) up to the present day. Because the subjects are initially grouped by their exposure, it is a cohort study. Because both the exposure and the disease outcome have already occurred before the investigator begins the study, it is designated as retrospective.

Step-by-Step Solution

1
Identify how the study population was initially grouped.
The subjects were categorized based on their exposure status to the synthetic resin (exposed versus unexposed) using historical HR logs.
Grouping subjects by exposure status rather than disease status is the defining characteristic of a cohort study.
2
Determine the temporal relationship between the study initiation, the exposure, and the outcome.
The investigator is conducting the study in 2026. Both the exposure (2000-2015) and the development of the outcome have already occurred in the past.
Because the investigator looks backward in time to establish the cohort based on past exposure and traces the outcomes up to the present day, the cohort study is retrospective.

Key Concept

A retrospective cohort study uses historical data to group subjects by past exposure status and then tracks the subsequent incidence of a disease up to the present.
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Topics

Study Design

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