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Evaluating Risk of Disease

Evaluating Risk of Disease. Bioterrorism Epidemiology Module 8 Missouri Department of Health And Senior Services. What Is Risk. A probability (likelihood) Comparing risk or likelihood of disease in exposure groups or likelihood of exposure in disease groups

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Evaluating Risk of Disease

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  1. Evaluating Risk of Disease Bioterrorism Epidemiology Module 8 Missouri Department of Health And Senior Services

  2. What Is Risk • A probability (likelihood) • Comparing risk or likelihood of disease in exposure groups or likelihood of exposure in disease groups • Relative risk and odds ratio are the most common measures of risk

  3. Relative Risk Incidence in the Exposed Group Incidence in the Non Exposed Group

  4. Relative Risk Disease + - a b + _ a + b Exposure c d c + d a/a+b c/c+d Incidence in Exposed RR = Incidence in Non Exposed

  5. Calculation of Person Years No. Years Of Observation 3 8 10 9 6 4 1 2 43 Person 1 2 3 4 5 6 7 8 Disease Status d nd nd d d nd nd nd Person Years

  6. Calculation of Person Years Person 1 2 3 4 5 6 7 8 No. Years Of Observation 3 8 10 9 6 4 1 2 43 Person Years

  7. Calculation of Person Years Person 1 2 3 4 5 6 7 8 No. Years Of Observation 3 8 10 9 6 4 1 2 43 Person Years

  8. Calculation of Person Years Person 1 2 3 4 5 6 7 8 No. Years Of Observation 3 8 10 9 6 4 1 2 43 Person Years

  9. Calculation of Person Years Person 1 2 3 4 5 6 7 8 No. Years Of Observation 3 8 10 9 6 4 1 2 43 Person Years

  10. Relative Risk Using Incidence Density Number Diseased Persons Person Years a b Exposed Not Exposed c d a/b c/d RR =

  11. Relative Risk Using Incidence Density Number Diseased Persons Person Years a b Exposed Not Exposed c d a/b c/d RR =

  12. Relative Risk Using Incidence Density Number Diseased Persons Person Years a b Exposed Not Exposed c d a/b c/d RR =

  13. Relative Risk Using Incidence Density Number Diseased Persons Person Years a b Exposed Not Exposed c d a/b c/d RR =

  14. Relative Risk Using Incidence Density Number Diseased Persons Person Years a b Exposed Not Exposed c d a/b c/d RR =

  15. Relative Risk Using Incidence Density Calculate the Relative Risk for this Data Diseased Persons Person Years 10 2000 Exposed 5 6000 Not Exposed

  16. Relative Risk Using Incidence Density Diseased Persons Person Years 10 2000 Exposed 5 6000 Not Exposed 10 / 2000 5 / 6000 RR = = 6.00

  17. Odds Ratios Can Estimate Relative Risk • Can be used in case control studies to evaluate the likelihood of exposure in two disease groups. • Can be used in cross-sectional studies to evaluate the likelihood of disease in two exposure groups when incidence data is not available.

  18. Odds Ratio (Case Control) Odds of Exposure in the Cases Odds of Exposure in the Controls

  19. Odds Ratio Case Control Study Exposed Non Exposed a b Cases c Controls d a / b c / d Odds of exposure in diseased OR = Odds of disease in non diseased

  20. Odds Ratio (Cross-Sectional Study) Odds of Disease in the Exposed Group Odds of Disease in the Non Exposed Group

  21. Odds Ratio Cross-Sectional Study Diseased Non-Diseased a b Exposed Non-Exposed c d a / b c / d Odds of disease in Exposed OR = Odds of disease in Non Exposed

  22. Relative Risk Cohort Study Calculate the relative risk for this data The Entire Population Diseased Non-Diseased Exposed 10,000 990,000 1,000,000 3,000,000 5,000 2,995,000 Non-Exposed 15,000 3,985,000 4,000,000

  23. Relative Risk Cohort Study Iexp = 10,000 / 1,000,000 X 100,000 =1,000 per 100,000 Inexp = 5,000 / 3,000,000 X 100,000 = 167 per 100,000 RR = Iexp / Inexp = 1,000 / 167 = 6.00 Diseased Non Diseased Exposed 10,000 990,000 Non-Exposed 5,000 2,995,000

  24. Odds Ratio Cross-Sectional Study Calculate the odds ratio for this data Diseased Non-Diseased Exposed 10,000 990,000 5,000 2,995,000 Non-Exposed

  25. Odds Ratio Cross-Sectional Study ODDS OF DISEASEexp = 10,000 / 990,000 = 0.01010 ODDS OF DISEASEnexp = 5,000 / 2,995,000 = 0.00167 OR = ODDSexp / ODDSnexp = 0.0101 / 0.0017 = 5.94 Diseased Non Diseased Exposed 10,000 990,000 Non-Exposed 5,000 2,995,000

  26. Relative Risk Cohort Study Calculate the RR for this data Diseased Non Diseased 750,000 1,000,000 Exposed 250,000 125,000 2,875,000 Non-Exposed 3,000,000 15,000 3,985,000 4,000,000

  27. Relative Risk Cohort Study Iexp = 250,000 / 1,000,000 X 100,000 = 25,000 per 100,000 Inexp = 125,000 / 3,000,000 X 100,000 = 4,167 per 100,000 RR = Iexp/Inexp = 25,000/4,167 = 6.00 Diseased Non-Diseased Exposed 250,000 750,000 Non-Exposed 125,000 2,875,000

  28. Relative Risk Cohort Study Calculate the OR for this data Diseased NonDiseased Exposed 750,000 250,000 125,000 2,875,000 Non-Exposed

  29. Relative Risk Cohort Study ODDS OF DISEASEexp = 250,000 / 750,000 = 0.3333 ODDS OF DISEASEnexp = 125,000 / 2,875,000 = 0.0435 OR = ORexp / ORnexp = 0.3333/0.0435 = 7.66 Diseased Non-Diseased 250,000 Exposed 750,000 Non-Exposed 125,000 2,875,000

  30. Odds Ratio Case Control Study Cases Controls a c Exposed b d Non-Exposed a / b c / d Odds of Exposure in Cases OR = Odds of Exposure in Controls

  31. Odds Ratio Case Control Study Calculate the Odds Ratio for this data Cases Controls Exposed 100 100 50 350 Non-Exposed

  32. Odds Ratios Case Control Study ODDS OF EXPOSUREcases = 100 / 50 = 2.0 ODDS OF EXPOSUREcontrols = 100 / 350 = 0.29 OR = ODDScases / ODDScontrols = 2 / 0.29 = 6.90 Cases Controls 100 100 Exposed Non-Exposed 50 350

  33. Dose Response Calculate the Odds Ratios using no exposure as your reference category Cases Controls 24 No Exposure 4 22 < One Year 28 12 1 - 10 Years 20 2 10 > 10 Years

  34. Dose Response Cases Controls OR No Exposure 4 100 24 --- 22 < One Year 28 7.6 1 - 10 Years 20 12 10.0 10 2 > 10 Years 30.0

  35. Dose Response (28/4) / (22/24) = 7.6 (20/4) / (12/24) = 10.0 (10/4) / (2/24) = 30.0 Cases Controls OR No Exposure 4 100 24 --- < One Year 22 28 7.6 1 - 10 Years 20 10.0 12 2 10 > 10 Years 30.0

  36. Attributable Risk (Risk Difference) Incidence in the Exposed – Incidence in the Non Exposed

  37. Attributable Risk As a Percentage Incidence in the Exposed – Incidence in the Non Exposed Incidence in the Exposed * 100 = %

  38. Comparison of Relative Risk and Attributable Risk Disease per 100,000 population Exposure Category Heavy Smokers Nonsmokers Lung Cancer 166 7 Coronary Heart Disease 599 422 Calculate the Relative Risk, the Attributable Risk, and the Percent Attributable Risk for this data.

  39. Comparison of Relative Risk and Attributable Risk Exposure Category Heavy Smokers Nonsmokers Lung Cancer 166 7 Coronary Heart Disease 599 422 Measure of Excess Risk Relative risk: Attributable risk Percent Attributable risk 599 422 166 7 = 23.7 = 1.4 166 – 7 = 159 599 – 422 = 177 159 166 177 599 = 30% = 96%

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