Epidemiology is the study of how health and disease are distributed in populations, and the factors that influence this distribution. It helps us understand patterns, causes, and risks associated with health conditions, guiding public health decisions, policy, and practice. Through research and data analysis, epidemiology plays a vital role in preventing illness, improving health outcomes, and shaping effective healthcare interventions at local, national, and global levels.
What they do: Describe what is happening.
Purpose: To find out who is affected, where, and when.
Examples:
Case Reports / Case Series: Detailed stories about one or a few patients.
Cross-Sectional Studies: A snapshot in time — like a survey showing how many people have asthma in a city today.
What they do: Investigate why something is happening.
Purpose: To explore causes, risks, or links between exposures (like smoking) and outcomes (like lung disease).
Main Types:
Cohort Study
Follows a group over time to see who develops a condition.
e.g. Track smokers and non-smokers for 10 years to see who develops lung cancer.
Case-Control Study
Starts with people who already have a condition and looks back to find what they were exposed to.
e.g. People with lung cancer vs. without — did they smoke?
Cross-Sectional (can be analytical too)
Can also look for associations at one point in time.
Correlational Study
Looks at patterns between variables — like countries with more exercise having less heart disease.
Shows a relationship, but not cause and effect.
What they do: Test an intervention or treatment.
Purpose: To see if something works.
Example:
Randomized Controlled Trial (RCT)
People are randomly put into groups — one gets the treatment, one doesn’t.
e.g. Test if a new vaccine prevents flu better than the old one.