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Incidence and Prevalence Measures of Disease Frequency Ayman Abou Mehrem, MD, CABP Neonatology Academic Day March 24, 2010
Objectives <ul><li>Importance of Measures of Disease Frequency </li></ul><ul><li>Prevalence </li></ul><ul><li>Incidence </...
Importance of Measures of Disease Frequency <ul><li>Prior to any clinical trial: </li></ul><ul><li>How frequently does the...
Prevalence <ul><li>The amount of a disease at one particular point in time </li></ul><ul><li>The  proportion  of people wh...
Prevalence <ul><li>What is the prevalence of anxiety disorder among UM medical student? </li></ul><ul><li>What is the prev...
Prevalence <ul><li>Prevalence measures </li></ul><ul><li>help to describe the  current burden  of a disease in a populatio...
Incidence <ul><li>The number of  new  cases of disease that develop over time </li></ul>
Incidence <ul><li>Two definitions </li></ul><ul><ul><li>Incidence proportion = </li></ul></ul><ul><ul><li>x 100% </li></ul...
Incidence <ul><li>What is the incidence of influenza infection among UM medical students (500 students) during a 3-month p...
Incidence <ul><li>Diagram of individual risk time and disease status </li></ul>
Incidence <ul><li>Incidence measures </li></ul><ul><li>help to provide clues as to the  cause  or  development  of a disea...
Relationship Between Prevalence and Incidence
Stratification <ul><li>Refers to the process of separating analysis by subgroups. </li></ul><ul><li>Stratification can be ...
Reference <ul><li>Epidemiology and Biostatistics: </li></ul><ul><li>An Introduction to Clinical Research </li></ul><ul><li...
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Incidence And Prevalence

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Incidence And Prevalence

  1. 1. Incidence and Prevalence Measures of Disease Frequency Ayman Abou Mehrem, MD, CABP Neonatology Academic Day March 24, 2010
  2. 2. Objectives <ul><li>Importance of Measures of Disease Frequency </li></ul><ul><li>Prevalence </li></ul><ul><li>Incidence </li></ul><ul><li>Relationship Between Prevalence and Incidence </li></ul><ul><li>Stratification of Disease Frequency by Person, Place, and Time </li></ul>
  3. 3. Importance of Measures of Disease Frequency <ul><li>Prior to any clinical trial: </li></ul><ul><li>How frequently does the disease occur? </li></ul><ul><li>Provide big picture information about a disease, framing public health questions and guiding resource allocation. </li></ul><ul><li>Describe the absolute risk of a disease. </li></ul><ul><li>Can be categorized, or stratified to gain insight into the pathogenesis (mechanism) of disease. </li></ul>
  4. 4. Prevalence <ul><li>The amount of a disease at one particular point in time </li></ul><ul><li>The proportion of people who have the disease </li></ul><ul><li>Prevalence (%) = </li></ul><ul><ul><li>×100% </li></ul></ul><ul><ul><li>number of people with disease </li></ul></ul><ul><ul><li>_____________________________ </li></ul></ul><ul><ul><li>number of people in the population </li></ul></ul>
  5. 5. Prevalence <ul><li>What is the prevalence of anxiety disorder among UM medical student? </li></ul><ul><li>What is the prevalence of cognitive disorders among school children born at < 34 wks GA in Manitoba? </li></ul>
  6. 6. Prevalence <ul><li>Prevalence measures </li></ul><ul><li>help to describe the current burden of a disease in a population in order to facilitate planning and resource allocation </li></ul>
  7. 7. Incidence <ul><li>The number of new cases of disease that develop over time </li></ul>
  8. 8. Incidence <ul><li>Two definitions </li></ul><ul><ul><li>Incidence proportion = </li></ul></ul><ul><ul><li>x 100% </li></ul></ul><ul><ul><li>Incidence rate (Incidence density) = </li></ul></ul><ul><ul><li>number of new cases of disease </li></ul></ul><ul><ul><li>_______________________________ </li></ul></ul><ul><ul><li>population without disease at baseline </li></ul></ul><ul><ul><li>number of new cases of disease </li></ul></ul><ul><ul><li>_____________________________ </li></ul></ul><ul><ul><li>person-time at risk </li></ul></ul>
  9. 9. Incidence <ul><li>What is the incidence of influenza infection among UM medical students (500 students) during a 3-month period from January through March 2009? </li></ul><ul><li>Time-at-Risk concept </li></ul>
  10. 10. Incidence <ul><li>Diagram of individual risk time and disease status </li></ul>
  11. 11. Incidence <ul><li>Incidence measures </li></ul><ul><li>help to provide clues as to the cause or development of a disease </li></ul>
  12. 12. Relationship Between Prevalence and Incidence
  13. 13. Stratification <ul><li>Refers to the process of separating analysis by subgroups. </li></ul><ul><li>Stratification can be by: </li></ul><ul><ul><li>Personal Characteristics: age, race/ethnicity, sex </li></ul></ul><ul><ul><li>Geography </li></ul></ul><ul><ul><li>Time periods </li></ul></ul>
  14. 14. Reference <ul><li>Epidemiology and Biostatistics: </li></ul><ul><li>An Introduction to Clinical Research </li></ul><ul><li>Bryan Kestenbaum; editors, K. Adeney, N. Weiss ; contributing author, Abigail B. Shoben </li></ul><ul><li>Springer Science+Business Media, LLC 2009 </li></ul>

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