Introduction to Epidemiology Terms

Question 1

What is epidemiology?

Answer 1

the study of health and illness in human populations

Question 2

What issues do you need to consider when planning a epidemiological research study?

Answer 2

1. Define a question
2. Variables (Exposure, Disease, and Control)
3. Design
4. Frequency
5. Effect
6. Bias
7. Analysis

Question 3

What is a determinant?

Answer 3

A variable that is predictive of a health outcome of interest; synonym for risk factor.

Question 4

What is the health outcome?

Answer 4

The possible health-related states or events of interest; the dependent variable of interest; in epidemiology, usually the disease variable being studied, although the outcome of interest may alternatively be mortality status, recovery from illness, or any health condition other than a disease.

Question 5

What are the control variables?

Answer 5

A variable other than the exposure variable that has a potential effect on the outcome variable and is subject to control in the analysis.

Question 6

Where do we obtain data to measure the variables?

Answer 6

Surveys
Interviews
Samples
Laboratories

Question 7

Clinical Trials

Answer 7

An epidemiologic design that most closely resembles a laboratory experiment; the major objective is to test the efficacy of a therapeutic or preventive intervention.

Question 8

Cross-sectional Study

Answer 8

all variables are studied at a single point or very short period of time

Question 9

Case-Control Study

Answer 9

starts with persons with a health outcome and looks back in time to determine prior exposure status

Question 10

Cohort Study

Answer 10

a group of individuals who share a common attribute are followed over time

Question 11

Rate

Answer 11

A measure of the rapidity with which health events such as new cases of disease or deaths occur; also called hazard and incidence density.

Question 12

Risk

Answer 12

The probability that an individual will experience an event of interest within a specified period of follow up

Question 13

Odds

Answer 13

The odds of an event is defined as P/(1-P) where P is the probability of the event, e.g., if P=1/3, then the odds equals 1/3 divided by 2/3, which equals 1/2, or 1 to 2.

Question 14

Prevalence

Answer 14

The proportion of persons in a defined population who have a particular health outcome, e.g., disease, at a point or during a period of time; existing cases of a disease.

Question 15

Disease frequency

Answer 15

How often a disease/health outcome occurs in a given study.

Question 16

Selection bias

Answer 16

Systematic error that results from the way subjects are selected into the study and/or because there are selective losses of subjects prior to data analysis.

Question 17

Bias

Answer 17

The presence of systematic error; a flaw in the study design, the methods of data collection, or the methods of data analysis that may lead to spurious conclusions about a exposure-disease relationship. Three general sources of bias occur in: the selection of study subjects, incorrect information gathered on study subjects and the failure to adjust for variables other than the exposure, commonly called confounding.

Question 18

Information bias

Answer 18

Systematic error resulting from incorrect information obtained on one or more variables measured or observed in a study. If all study variables of interest are categorical (e.g., dichotomous), then information bias is called misclassification bias.

Question 19

Confounding Bias

Answer 19

Bias resulting from failure to control for other variables in assessing an exposure-disease relationship.