3. MTB Step 3 - Incidence & Prevalence

Question 1

DEFINITION:

Incidence

Answer 1

The RATE at which New Diseases occur:

Incidence = # of new cases / amt. of unit time.

Examples:

1. 20,000 new diabetic patients per week in the United States (interval data).
2. 750,000 cases of myocardial infarction per year in the U.S. (interval data).
3. There is 1 new case of Creutzfeld-Jakob disease per 1 million people in the population every year (ratio data).
4. There is 1 new case of Multiple Sclerosis (MS) for every 1,000 people in the population every year (ratio data).

Question 2

DEFINITION:

Prevalence

Answer 2

The TOTAL number of All Cases in a population at a specific Point in Time:

Prevalence = # of all cases / specific point in time

Examples:

1. There are 30 million people in the United States living with diabetes.

Question 3

Explain how Incidence and Prevalence are directly related:

Answer 3

The Incidence of 20,000 new diabetes cases per week, or 1 million new cases per year, generates a Prevalence of 30 million cases.

Question 4

Do medical therapies that Lower Mortality change the Incidence of disease?

Answer 4

Nope!

Question 5

Do medical therapies that Lower Mortality change the Prevalence of disease?

Answer 5

YEP!

When there is Less disease Mortality, patients with a disease Live Longer and thus INCREASE its Prevalence.