1 / 78

WARM-UP

WARM-UP. Cohort Study. Kaijuan Wang 2008.11 . Cohort Study. Wenjie Yang ywjie@zzu.edu.cn 2004.12. Hypothesis. Analytical Epidemiology. Judging Causality. Prevention Strategies. Concept Map. Descriptive Epidemiology. Cross-Sectional Survey. Cohort Study. Case-control study.

millie
Download Presentation

WARM-UP

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. WARM-UP

  2. Cohort Study Kaijuan Wang 2008.11

  3. Cohort Study Wenjie Yang ywjie@zzu.edu.cn 2004.12

  4. Hypothesis Analytical Epidemiology Judging Causality Prevention Strategies Concept Map Descriptive Epidemiology Cross-Sectional Survey Cohort Study Case-control study Experimental Epidemiology

  5. Cohort Study ★Postulate of Cohort Study ★Designing of Cohort Study ★Analysis of Cohort Study

  6. ★Postulate of Cohort study Definition of cohort Cohort: A group of people who share a common experience or condition. e.g. A cohort of smoker; A cohort of drug addict A cohort of A type behavior

  7. Cohort study:people who are free of disease are classified into two (or more) groups according to whether they are expose to a suspected factor or not(or different levels of the exposure) , and are followed over a period of time, the association between exposure and disease is evaluated by the difference of incidence rates of the two(or more) groups.

  8. smokers Lung cancer diseased Ie= exposed Follow-up diseased I0= Unexposed

  9. Types of cohort studyProspective Cohort Study Retrospective Cohort Study Ambispective Cohort Study

  10. Prospective Cohort Study diseased exposed nondiseased Initiation of study d unexposed nd now future

  11. Retrospective Cohort Study diseased exposed nondiseased Initiation of Study last d now unexposed nd

  12. Ambispective Cohort Study diseased exposed nondiseased Initiation of Study d now unexposed future nd Last

  13. Comparison Prospective cohort study Retrospective cohort study surveyed personally collected from historical records higher authenticity lower authenticity time-consuming time-saving expensive economic .

  14. ★ Design of cohort study 1 Ascertain the research goal 2 Define the exposure and fix on the measure method 3 Ascertain the research type 4 Ascertaina proper sample size

  15. A cohort study is to conducted to reveal the association between X-ray and leukaemia.We have know that: 1. the incidence rate of leukaemia in general population is 1 per 10 thousand approximately; 2. the incidence rate of leukaemia in X-ray exposed population is10 per 10 thousand approximately; Required:α=0.05 β=0.10 (Zα =1.96 Z β=1.28) An example

  16. P1 =0.0001, Q1=1-0.0001=0.9999 P2 =0.001, Q2=1-0.001=0.999 N=14247

  17. 5 Select research subject 5.1 Select the exposed group (1) From particular group A population that have a high level of exposure.

  18. ionic radiation leukemia radiologist uranium miner Atomic-bomb survivor

  19. 1) exposure is rare in general population,but relates to particular occupations , locations,life styles or experiences. 2) less time and less expense needed

  20. (2) From general population: 1) Exposure is relatively common . E.g. Smoking Tea drinking 2) Interested in the effect of moderate or low level of exposure

  21. 5.2 Selection of the comparison group Principle: Comparison group do not have exposure and should be as similar as possible with the exposed group except for the exposure .

  22. (1) internal comparison exposed inhomogeneous unexposed

  23. (2)external comparison exposed exposed Sampling inhomogeneous unexposed

  24. 6 Screen the subjects and collect the baseline data Screening of the subjects: exclude the subjects who have had the disease of interest collection of the baseline data: The exposure status Other risk factor status

  25. (1) Beginning of follow-up Latency period: the period between the initiation of exposure and the ascertainment of outcome (disease of interest) 7 Follow-up

  26. (2) Period of follow-up Depend on Strength of the association between exposure and disease

  27. (3)interval of follow-up Depend on stability of exposure status and the span of minimum latency period and maximum latency period

  28. (4) Task of follow-up exposure status outcome other risk factor exposure status

  29. (5) Main Methods of follow-up : ① Utilize varied routine record ② family interview ③ telephone or correspond inquiry

  30. ★Analysis of Cohort Study • 1 Measures of disease frequency (1) In fixed cohort(the status of participants is changeless) CI(cumulative incidence): The proportion of individuals who become diseased during a specified time period.

  31. number of new cases of a disease during the follow-up period CI= number of participants at the initiation of follow-up

  32. In a study of oral contraceptive use and bacteriauria, a total of 2400 women aged from 16 to 49 years were identified who were free from bacteriauria. Of these, 400 were OC users at the initiation. 3 years later,20 of the OC users had developed bacteriauria. • 3-year period CI=20/400=5.0%

  33. (2) in dynamic population(the status of participants is protean) ID(incidence density) :when the denominator is sum of person-time at risk, the incidence rate is called as ~.

  34. number of new cases of a disease during the follow-up period ID= total person-time of observation

  35. Jan, July, Jan, July Jan, July, Jan, July person 1998 1998 1999 1999 2000 2000 2001 2001 time A 2 B 2.5 C 2 D 3.5 Total person-time 10

  36. Exposed population General population Unexposed population

  37. Measures of association 1 RR (Relative Risk) ratio of the risk (i.e., incidence rate) in an exposed population to the risk in an unexposed, but otherwise similar, population. Incidence（exposed） RR= Incidence（unexposed）

  38. indicator of the strength (biological significance) of an association between an expose and disease.

  39. RR>1 Research factor is a risk factor (Positive association) RR<1 Research factor is a protective factor (Negative association ) RR=1 No association between the factor and the disease. Incidence（exposed） RR= Incidence（unexposed）

  40. strength no low middle high More higher

  41. For example, a relative risk of 2 associated with a risk factor means that persons with that risk factor have a doubled risk of having a specified outcome compared to persons without that risk factor.

  42. BreastNo Breast Cancer Cancer Total Alcohol 702,930 3,000 No alcohol 502,950 3,000 50 / 3,000 RR using Cumulative Incidence (CI): 70 / 3,000 RR = 1.4 =

  43. Smoking population Infinite population samples Non-smoking population

  44. Statistics: p-value indicates the likelihood that a study’s findings are due to chance in data analysis, RR =2.6, p=0.001 0.1% probability that the observed RR was a chance finding

More Related