Epidemiology Vocabulary Page

Case.  The occurrence of a pre-defined health problem in a person.

Case Control Study.  A study type that uses cases (with the health problem) and compares them with controls (without the health problem) to find out what may have caused the problem.  A type of retrospective study (see below).

Case Definition.  A way to describe who has the health problem by place and time.  For example, researchers defined a case as a baby born in Cameron County between 1986 and 1991 with a diagnosis of anencephaly.   

Cluster.  A group of cases close in time and place.

Diagnosis.   A judgment about the name and type of illness affecting a person.

Epidemiology.   The study of disease and health in human populations.

Experimental study.  A testing study.  The study asks groups of people to try treatments, and then looks at which treatment leads to better health.

Hypothesis.  An educated guess made after information is gathered and viewed.  Research is done to test whether the hypothesis is true or not.

Observational Study.  A study that watches people to see if their health habits or traits relate to diseases.  The researcher does not change a person's habits or give them any treatments as in an experimental study.  There are two types, prospective and retrospective.   

Prospective Study.  A study that starts to watch people over time in the future.  The study looks at the habits of a group of people and then follows them to see who gets a disease and who doesn't. 

Retrospective Study.  A study type that finds people with and without a disease and then goes back to find out if their health habits could have caused the disease. 

Prevalence Rate.   The number of all current cases in a population during a certain time.

Relative Risk. A comparison of the risk of disease in one group compared to the risk of disease in another group.  In one study, the relative risk for anencephaly in a baby whose mother did not take folic acid was three times the risk in a baby whose mother did take folic acid.  

Risk Factor.  Personal behavior or lifestyle, an environmental exposure, or a family trait that might cause or add to a health problem.