What is the study design of a 20-year follow-up study comparing cancer occurrence in 30/500 babies exposed to Di-ethyl-stilbestrol (DES) in utero to 1500 unexposed babies?

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Study Design for DES Exposure and Cancer Risk Research

The study described is a cohort study (Option A).

Characteristics of the Study Design

This research follows the classic structure of a cohort study, which has several defining features evident in the scenario:

  • Exposure-based selection: The study selected participants based on their exposure status (exposed to DES in utero vs. unexposed) rather than disease outcome
  • Temporal sequence: The exposure (DES in utero) clearly preceded the outcome (cancer occurrence)
  • Prospective follow-up: Both groups were followed forward in time for 20 years to observe cancer development
  • Comparison of incidence: The study compared cancer occurrence rates between exposed and unexposed groups

Why This Is Not Other Study Designs

  • Not case-control (B): In a case-control study, participants would be selected based on disease status (having cancer vs. not having cancer) and then their past exposure to DES would be assessed retrospectively
  • Not cross-sectional (C): Cross-sectional studies measure exposure and outcome at the same point in time, whereas this study had a 20-year follow-up period
  • Not correlation study (D): Correlation studies examine relationships between variables at the population level without individual-level data

Key Elements of the Cohort Design in This Study

  1. Defined cohorts:

    • Exposed cohort: 30/500 babies exposed to DES in utero
    • Unexposed cohort: 1500 babies not exposed to DES

  2. Longitudinal follow-up:

    • Both groups were followed for the same 20-year period

  3. Specific outcome measurement:

    • The occurrence of cancer was the primary outcome measured

  4. Comparative analysis:

    • The study design allows for calculation of relative risks and attributable risks

Advantages of This Study Design

  • Establishes temporal relationship between exposure and outcome
  • Allows calculation of incidence rates in both exposed and unexposed groups
  • Suitable for studying rare exposures (like DES in utero)
  • Can examine multiple outcomes from a single exposure

Limitations of This Study Design

  • Requires large sample sizes, especially for rare outcomes
  • Potential for loss to follow-up over the 20-year period
  • May be affected by confounding factors that influence both exposure and outcome
  • Expensive and time-consuming due to long follow-up period

Cohort studies are particularly valuable for studying the long-term effects of prenatal exposures like DES, as they allow researchers to establish clear temporal relationships between the exposure and subsequent health outcomes.

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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