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Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
Epidemiological studies
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Epidemiological studies

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  • Ask the learners to define Epidemiology
  • Health related states include disease and non-disease states. Example of non-disease states – injury, substance use, suicide
  • Ask learners to explain the uses of epidemioloy
  • Transcript

    • 1. EPIDEMIOLOGICAL STUDIES 1
    • 2. OUTLINE Classification of studies Study Designs and analysis Choice of study design 2
    • 3. CLASSIFICATION 3
    • 4. CLASSIFICATION Various ways BUT, two major classes  Non-Interventional  Interventional 4
    • 5. Non-Intervention studies Researcher do not manipulate situations/objects  Just describes or analyses situations/objects 5
    • 6. Intervention studies Researcher manipulates situations/objects then describes or analyses the outcome 6
    • 7. STUDY DESIGNS AND ANALYSIS 7
    • 8. Non-Intervention studies 8
    • 9. Types of Non- Interventional studies Exploratory Descriptive Analytical 9
    • 10. Exploratory studies Small scale studies Gathers information about unfamiliar phenomenon Results gives insight to a problem before a large scale study is designed 10
    • 11. Descriptive studies Only describe phenomena: e.g. Person, Place, Time No analysis of determinants/association  E.g. Cross-sectional descriptive 11
    • 12. Cross-sectional descriptive Aim at just describing phenomenon Done at one point in time – hence Cross-sectional  E.g. Prevalence studies, KAPB studies 12
    • 13. Analytical studies Describe phenomena  And Analyze relationship between phenomena and other variables (determinants/association).  Examples:  Cross-sectional comparative  Cohort study  Case-control study 13
    • 14. Cross-sectional comparative study Aim at describing phenomenon and compare groups or determine factors influencing the phenomenon Done at one point in time Measurement of exposure and effect are done at the same time 14
    • 15. Advantages and Disadvantagesof Cross-sectional studiesAdvantages Disadvantages Quick and cheap  Not possible to determine Can elucidate various if the exposure preceded exposures, as first the outcome (temporal step in investigating relationship) cause  Bias** Repeated measures can depict trend Data useful in assessing health care needs 15
    • 16. Cohort studies 16
    • 17. Cohort study (“Prospective, “Followup” study) Aim at determining risk factors for diseases/outcome At the start identify two groups  With exposure to a risk factor (exposed)  Without exposure (no-n exposed) Both groups have not developed the disease/outcome at the start Follow over time At the end, analyse disease/outcome occurrence in both groups and compare 17
    • 18. Design of Cohort study - I Time Inquiry Disease Start Exposed No diseasePopulation Non-diseased people Non-exposed Disease No disease 18
    • 19. Design of Cohort study - II Exposed and non-exposed groups must be comparable in all factors that may be related to the disease except for the exposure Need to get complete and accurate information about exposure and outcome for all individuals 19
    • 20. Analysis of Cohort studies Compare incidences of disease among exposed to non-exposed group  Cumulative incidence (Calculate Relative Risk) (commonly)  Incidence rate (Calculate Incidence rate ratio), - when person time of follow up is known 20
    • 21. Advantages & Disadvantages Advantages  Disadvantages  Allows direct  Time consuming, measurement of expensive incidence of disease  Inefficient in  Multiple effects of evaluating rare single exposure can be diseases examined  Loss of follow up affect  Can elucidate temporal validity of results relationship between exposure and disease  Is of value when exposure is rare  Minimize bias in ascertainment of exposure 21
    • 22. Case – control studies 22
    • 23. Case –control study(“Retrospective” study) Aim at determining risk factors for diseases/outcome At the start identify two groups  With disease/outcome (Cases)  Without disease/outcome (Controls) History of exposure to risk factor is inquired At the end, analyse exposures to a risk factor in both groups and compare 23
    • 24. Design of Case-control study - I Time Start Inquiry Exposed Cases Non exposed Population Exposed Controls Non expose 24
    • 25. Design of Case-control study - II Controls should be representative of the population from which the cases are recruited Cases and controls must be comparable in all factors that may be related to the disease except for presence of disease Controls can be chosen to match cases for certain important variables such as age, sex, etc = Matched Case-control design. If matching not done = Un- matched case-control design (more common) Need to get complete and accurate information about exposure for all individuals Control: Case ratio? Consider cost, availability of cases Usually ratio of 1:1 up to 4:1, beyond that no added advantage for power of the study 25
    • 26. Analysis of Case-control studies Compare Exposure of disease among Cases to Controls  Calculate Odds Ratio 26
    • 27. Advantages & Disadvantages Advantages  Disadvantages  Relatively quick  Inefficient in and inexpensive evaluating rare  Suitable for rare exposures diseases  Temporal  Can evaluate relationship effect of multiple between exposure exposures and disease difficult  Is of value for to ascertain diseases with long  Prone to recall bias latent periods 27
    • 28. Intervention studies 28
    • 29. Intervention studiesTwo main types: Experimental (Classical experiment) Quasi-experimental 29
    • 30. Characteristics of Experimental studies  Manipulation  Something is done to one group (experimental group)  Presence of Control group (no manipulation done)  Randomization (assignment of individuals to experimental or control groups is done randomly)  Example: Randomized Controlled Trials (RCT) – “Gold standard” 30
    • 31. Characteristics of Quasi-Experimentalstudies Manipulation Control group or Randomization missing  Example: Community trials 31
    • 32. Design of Randomized controlled trial - I Exp. group Follow up & Study AnalysisGeneral pop Randomization PX Control group 32
    • 33. Design of Randomized controlled trial - II Randomization ensures that chance alone determines which individuals become experimental group and which ones become control group  Thus, making the groups comparable in most aspects that may be related to the outcome Design provide strong evidence of the effect of the intervention – “Gold standard” Study participants are blinded about the intervention (Single blind) Sometimes both Study participants and investigators are blind about the intervention (Double-blind) 33
    • 34. Ethical Considerations in Experimental studies Carried out only if:  Evidence suggest intervention is beneficial, but uncertain of effect  No serious adverse effect to the intervention group  Informed consent to participate 34
    • 35. Analysis of Intervention studies Comparison of outcome of interest in experimental and control groups Comparison of baseline characteristics of experimental and control groups 35
    • 36. Choosing a study designConsiderations: Ethical issues – minimal ethical concerns Resources and administrative issues Validity and reliability of results Nature of topic 36

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