Define what a cause is in epidemiology.

• A. The disease itself.
• B. A factor that produces a change in the severity or frequency of the outcome.
• C. A random association.
• D. A factor that prevents disease.

Answer: (B)

In epidemiology, a cause is a factor that changes the probability or severity of the outcome occurring. It isn’t the disease itself, and it isn’t just a random association or a factor that helps prevent disease. A true causal factor alters how often the disease happens or how severe it is, and it can be a necessary component, a sufficient component, or part of a set of interacting factors that together produce the outcome.