Epidemiological Studies Overview

Definition of a Study

• A study is a scientific process to answer a question using data from a population.
• Examples of questions include:
  • Does smoking cause cancer?
  • Is there more disease in one area compared to another?
  • What food is causing an outbreak?
• Steps in conducting a study:
  1. Formulate a study question.
  2. Determine the best study type to answer the question.
  3. Conduct the study, collect, and analyze data using statistical methods.
  4. Interpret results.
  5. Report results ethically.

Types of Epidemiological Studies

Ecological Studies

• Measurements are on groups rather than individuals.
• Useful for comparing population health across different regions or times.
• Advantages:
  • Highlight issues for future studies.
• Disadvantages:
  • Results apply only to groups, not individuals.

Case Series

• Describes characteristics of a group with the same disease/exposure.
• Used to understand demographics, clinical presentation, and prognosis.
• Example: Identification of HIV through unusual pneumonia cases in the 1980s.

Cross-Sectional Studies

• Measures health information from a population at a single point in time.
• Also known as prevalent studies.
• Advantages:
  • Inexpensive and easy to conduct.
  • Provide information on multiple exposures and outcomes.
• Disadvantages:
  • Cannot determine causality.

Case-Control Studies

• Compares people with a disease (cases) to those without (controls).
• Investigates previous exposures to risk factors.
• Uses odds ratio to determine possible causes.
• Advantages:
  • Quick and inexpensive.
  • Suitable for uncommon diseases.
• Disadvantages:
  • Not good for studying rare exposures.
  • Recall bias in exposure history.

Cohort Studies

• Follows a group over time to see outcomes based on exposures.
• Uses relative risk to compare disease risk between exposed and unexposed groups.
• Advantages:
  • Determine time sequence of events.
  • Collect information on multiple outcomes and risk factors.
• Disadvantages:
  • High cost and long duration.
  • Dropouts can affect results.

Interventional Studies

• Intervention is applied to a group, and outcomes are studied.
• Randomized controlled trials are ideal.
• Advantages:
  • Strong evidence for causality.
  • Randomization minimizes bias.
• Disadvantages:
  • Expensive and may require many participants.
  • Ethical concerns in some situations.

Systematic Reviews and Meta-Analyses

• Systematic Review: Identifies and synthesizes all relevant studies on a topic.
• Meta-Analysis: Combines statistical data from similar studies to provide a summary result.

Conclusion

• Overview of epidemiological study types, their processes, advantages, and disadvantages.