Epidemiology

Core Concepts and Examples

1. Incidence

1. • Definition

     1. The number of new cases of a disease/condition in a period of time

   • Example

     1. There are 30 new diagnoses lung cancer per 100,000 people each year.

2. Prevalence

   • Definition

     1. The number of cases, old and new, of a disease/condition in a period of time

   • Point

     1. Definition

        • The number of cases, old and new, at a specific point in time

     2. Example

        • There were 50 cases of lung cancer per 100,000 people on January 1st, 2018

   • Period

     1. Definition

        • The number of cases, old and new, through a specific period

     2. Example

        • There were 50 cases of lung cancer per 100,000 people through 2017

   • Lifetime

     1. Definition

        • The number cases that will occur over a lifetime

     2. Example

        • 20 out of every 100,000 people will be diagnosed with cancer in their lifetime

3. Mortality

   • Definition

     1. Incidence of death or number of deaths as a result of the condition in question out of the whole population in a specific amount of time.

   • Example

     1. 20 out of every 100,000 people will die of lung cancer this year

4. Case Fatality (aka just Fatality)

   • Definition

     1. The proportion of people with the disease who will die

   • Example

     1. 50% of people with lung cancer will die

5. Survival

   • Definition

     1. The proportion of people with the disease who will not die

   • Example

     1. 50% of people with lung cancer will live