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What is Epidemiology?


Updated July 30, 2012


Epidemiology is the study of how diseases and other health conditions progress throughout a specific population. Using statistical analysis, epidemiologists examine the incidence of a disease or injury, analyze who is affected within a given group of people, and use this information to calculate the rate, and risk, of disease in that population.

According to the US Centers for Disease Control (CDC)–- a federal agency established to monitor health, investigate disease development and make recommendations on prevention – epidemiology is the basic science concerned with public health, and how groups of people (rather than individuals) are affected. It has moved from its early focus on infectious diseases to a much broader perspective involving environmental factors, human behavior, injuries and chronic conditions.

Here are some branches of the current study of epidemiology being employed around the world:

  • Descriptive epidemiology: Health events are examined in terms of what the problem is, who gets it, where they get it, and when they get it, to establish the pattern or spread of the disease or condition.
  • Analytical epidemiology: Identifying which specific factors determine how and why a disease spreads –- to decide who is at greatest risk -- is the focus of analytical epidemiology.
  • Applied epidemiology: Using statistical data to shape public health policy and interventions that will minimize illness and disability is the aim of applied or field epidemiology.

Much of what we have learned about human longevity, and which factors play the greatest role in extending our lifespan and helping us avoid disease, has been gleaned from epidemiological studies and longitudinal research.

Read more about how a longitudinal study gets launched


An Introduction to Epidemiology. US Centers for Disease Control Public Information Sheet. Accessed July 28, 2012.

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