What is the Role of Epidemiology in Nursing? A Simple Guide

Introduction of epideiology

• Etymology: From Greek — “epi” (among), “demos” (people), “logos” (study).
• Father of Modern Epidemiology: John Snow, who studied the 1854 cholera outbreak in London.
• Institute Mentioned: National Institute of Epidemiology – Chennai.

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Definition

“Study of the distribution and determinants of disease frequency in man.” — MacMahon (1960)

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Epidemiological Triad

Used to explain infectious disease transmission:

1. Agent – e.g., virus, bacteria (Plasmodium in malaria)
2. Host – the human who gets sick
3. Environment – e.g., stagnant water (mosquito breeding site)

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Objectives of Epidemiology

• Identify disease causes
• Study disease patterns (who, where, when)
• Find risk factors
• Evaluate prevention/control methods
• Provide data for health planning

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Types of Epidemiological Studies

1. Descriptive Study

• Describes “who, where, when”
• Example: Diarrhea in children in a village in July

2. Analytical Study

• Finds cause/reason by comparing groups

A. Case-Control Study

• Type: Observational, retrospective
• Groups: Cases (with disease) vs Controls (without)
• Purpose: To find associations between exposure & disease
• Steps:
  1. Define case
  2. Select controls
  3. Match variables
  4. Assess exposure
  5. Analyze data
  6. Calculate Odds Ratio (OR)

OR Interpretation:

• OR > 1: Risk factor present
• OR < 1: Protective factor
• OR = 1: No association

Advantages:

• Good for rare diseases
• Cost & time efficient

Disadvantages:

• Recall & selection bias
• Can’t calculate incidence
• Temporal ambiguity

Example: Smoking and lung cancer

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B. Cohort Study

• Starts with healthy people only
• Follow exposed vs unexposed groups over time
• Prospective study
• Example: Follow smokers and non-smokers for 10 years

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C. Cross-Sectional Study

• Snapshot at one time
• Checks current disease status and risk factors
• Example: Survey for high BP and diet habits

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3. Experimental (Interventional) Study

• Intervention is applied (e.g., new vaccine vs placebo)
• Often in clinical trials

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