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Nested case control study

Nested case control study. 分析流行病學方法的詳細分類. Cohort study. 過去. 現在. 未來. Case control study. 過去. 現在. 未來. Nested case control study. 過去. 現在. 未來. Disease risk in exposed. Risk exposure. Disease risk in nonexposed. Risk nonexposure. Relative Risk ( FOR COHORT). Definition:

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Nested case control study

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  1. Nested case control study

  2. 分析流行病學方法的詳細分類

  3. Cohort study 過去 現在 未來

  4. Case control study 過去 現在 未來

  5. Nested case control study 過去 現在 未來

  6. Disease risk in exposed Risk exposure Disease risk in nonexposed Risk nonexposure Relative Risk ( FOR COHORT) • Definition: • The ratio of the risk of disease in persons exposed compared to the risk of disease in persons unexposed • Common formula of relative risk (RR) RR= = • Diseased risk: cumulate rate(incidence), rate(incidence) density • relative risk; rate ratio; risk ratio…

  7. Incidenceexposed No Disease Relative Risk = Disease Incidenceunexposed A B a + b =N1 Exposed Unexposed C D C + D =N0 Incidence Densityexposed A + C B + D N Rate Ratio = Cumulative Incidenceexposed Incidence Densityunexposed A/N1 Risk Ratio = Risk Ratio = Cumulative Incidenceunexposed C/N0 Ex Dx Ex.

  8. Interpretation of Relative Risk • RR > 1 - the risk of disease in the exposed group is greater than the risk in the unexposed group • RR = 1 - the risk of disease is the same in the exposed and unexposed • RR < 1 - the risk of disease in the exposed group is less than the risk in the unexposed

  9. No Disease Disease A B N1 Exposed Unexposed C D N0 A + C B + D N For Fixed Cohort Equal follow-up time: 不考慮time • Cumulate incidence • 研究對象發病的機率(risk) • CI1 = A/N1 • CI0 = C/N0 • RRCI = CI1/CI0 • = (A/N1)/(C/N0) • RDCI = CI1- CI0 • = (A/N1) - (C/N0) ORCI = CI1(1-CI1) / CI0 (1-CI0) = AD/BC

  10. Observed Person-years Disease A L1 N1 Exposed Unexposed C L0 N0 A + C = m1 L1 + L0 = L N For Dynamic Cohort Unequal follow-up time: 考慮 time • Incidence density • 單位人時的發病狀況(rate) • ID1 = A/L1 • ID0 = C/L0 • RRID = ID1/ID0 • = (A/L1)/(C/L0) • RDID = ID1- ID0 • = (A/L1) - (C/L0) No odds

  11. Dx/non-Dx in exposured Exposure/unexposure in Dx Dx ratioexposed Ex ratiodisease Dx/non-Dx in unexposured Dx ratiounexposed Exposure/unexposure in nonDx Ex rationon-Dx Odds Ratio (FOR CSCN) • Definition: • The ratio of the ratio of exposure in diseased persons compared to the ratio of exposure in non-diseased persons • Common formula of odds ratio (OR) OR.cohort = = = OR.cs-cn=

  12. No Disease Disease a b a + b Exposed c d c + d Unexposed a+c b + d a+b+c+d case-control study Dx Ex Odds(Dx)=(a/a+c)/(c/a+c) Odds(nonEx)=(b/b+d)/(d/b+d) Odds Ratio = odds(Dx)/odds(nonDx) = a*d/b*c ~ A*D/B*C

  13. Interpretation of Odds Ratio • OR > 1 - the odds of exposure in the diseased group is greater than the risk in the non-diseased group • OR = 1 - the odds of exposure is the same in the diseased and non-diseased • OR < 1 - the odds of exposure in the diseased group is less than the risk in the non-diseased group

  14. In case-control study of 74 Endometrial Cancer patients & their 664 controls, 56 cases and 274 controls received estrogen therapy ever. • OR=? EX-3

  15. No Cancer Cancer 56 330 274 Estrogens No Estrogens 18 390 408 664 74 738 Odds ratio = 56*390/18*274 = 4.42 Estrogens and Endometrial Cancer EX-3

  16. Why does Odds Ratio represent Relative Risk ? Relative Risks and Odds RatiosWhen are They Similar?

  17. Random sample; case-control study No Disease No Disease Disease Disease A a b B A + B=N1 a + b Exposed Exposed C c d D C + D=N0 c + d Unexposed Unexposed a+c A + C b + d B + D N a+b+c+d Population; Cohort study Odds(Ex)=(A/N1)/(1-A/N1) Odds(nonEx)=(C/N0)/(1-C/N0) Odds Ratio = odds(Ex)/odds(nonEx) = A*D/B*C Odds(Dx)=(a/a+c)/(c/a+c) Odds(nonEx)=(b/b+d)/(d/b+d) Odds Ratio = odds(Dx)/odds(nonDx) = a*d/b*c ~ A*D/B*C Dx Ex

  18. If case & control from fixed cohort • Assumption: • Case and control are random sample from diseased & non-diseased population (representative) • Probability (ex CI) is very small (rare disease)

  19. Persons- Years Disease A L1=N1*t1 Exposed C L0 = N0*t0 Unexposed A + C L1 + L0 = L If case & control from dynamic cohort • Assumption: • Case and control are random sample from diseased & non-diseased population (representative) • Density sampling (time-matching) If t0=t1, Odds(Ex)=(A/N1) Odds(nonEx)=(C/N0) Odds Ratio = (A/N1)/ (C/N0) = (A/L1)/ (C/L0) = RRID

  20. OR 的估計在 case 及control都具 population的representative 的時候，可以用來估計RR。 • Cscn study 的control選擇，用incident case 比用 prevalent case好

  21. Example: Tissue plasminogen activator antigen and D-dimer as markers for atherosclerobotic risk among healthy postmenopausal women Circulation. 2004

  22. Cohort – WHI-OS • Bw 1994~1998, 93724 women aged 50 to 79 y/o from 40 clinical centers throughout USA. • Participants: • having no prior history of CVD or cancer. • Monitoring over an average follow-up of 2.9 years.

  23. Design of this nested cs-cn study Fw-up time= 2.9y CHD event, CHD death 315 Case Cohort were recruited Match criterion: Age, smoking, ethnicity, follow-up time Baseline: Qns, blood, dx history, HRT history,…. 315 Control from cohort

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