Incidence and prevalence measures provide information about disease frequency and burden in populations. Prevalence describes the proportion of people with a disease at a point in time, while incidence refers to the number of new cases that develop over time. Both measures can be stratified by person, place, and time to gain insights into a disease's pathogenesis and development.

1. Incidence and Prevalence Measures of Disease Frequency Ayman Abou Mehrem, MD, CABP Neonatology Academic Day March 24, 2010

2. Objectives Importance of Measures of Disease Frequency Prevalence Incidence Relationship Between Prevalence and Incidence Stratification of Disease Frequency by Person, Place, and Time

3. Importance of Measures of Disease Frequency Prior to any clinical trial: How frequently does the disease occur? Provide big picture information about a disease, framing public health questions and guiding resource allocation. Describe the absolute risk of a disease. Can be categorized, or stratified to gain insight into the pathogenesis (mechanism) of disease.

4. Prevalence The amount of a disease at one particular point in time The proportion of people who have the disease Prevalence (%) = ×100% number of people with disease _____________________________ number of people in the population

5. Prevalence What is the prevalence of anxiety disorder among UM medical student? What is the prevalence of cognitive disorders among school children born at < 34 wks GA in Manitoba?

6. Prevalence Prevalence measures help to describe the current burden of a disease in a population in order to facilitate planning and resource allocation

7. Incidence The number of new cases of disease that develop over time

8. Incidence Two definitions Incidence proportion = x 100% Incidence rate (Incidence density) = number of new cases of disease _______________________________ population without disease at baseline number of new cases of disease _____________________________ person-time at risk

9. Incidence What is the incidence of influenza infection among UM medical students (500 students) during a 3-month period from January through March 2009? Time-at-Risk concept

10. Incidence Diagram of individual risk time and disease status

11. Incidence Incidence measures help to provide clues as to the cause or development of a disease

12. Relationship Between Prevalence and Incidence

13. Stratification Refers to the process of separating analysis by subgroups. Stratification can be by: Personal Characteristics: age, race/ethnicity, sex Geography Time periods

14. Reference Epidemiology and Biostatistics: An Introduction to Clinical Research Bryan Kestenbaum; editors, K. Adeney, N. Weiss ; contributing author, Abigail B. Shoben Springer Science+Business Media, LLC 2009