1. Causal relationships, bias, and research designs Professor Anthony DiGirolamo

2. Causal Relationships

3. Sufficient Cause

4. Causal Relationships Sufficient Cause Precedes diseases, factor always present with disease

5. Causal Relationships Sufficient Cause Precedes diseases, factor always present with disease Necessary Cause

6. Causal Relationships Sufficient Cause Precedes diseases, factor always present with disease Necessary Cause Factor must be present for disease, but factor can be present without developing disease

7. Causal Relationships Sufficient Cause Precedes diseases, factor always present with disease Necessary Cause Factor must be present for disease, but factor can be present without developing disease Risk Factor

8. Causal Relationships Sufficient Cause Precedes diseases, factor always present with disease Necessary Cause Factor must be present for disease, but factor can be present without developing disease Risk Factor An exposure, behavior, or attribute that, if present, clearly influences the probability of disease

9. Determining Cause and Effect

10. Mill’s Cannons

11. Determining Cause and Effect Mill’s Cannons Strength Association shows a large difference

12. Determining Cause and Effect Mill’s Cannons Strength Association shows a large difference Consistency Association is always present with the disease

13. Determining Cause and Effect Mill’s Cannons Strength Association shows a large difference Consistency Association is always present with the disease Specificity No disease if the factor isn’t present

14. Determining Cause and Effect Mill’s Cannons Strength Association shows a large difference Consistency Association is always present with the disease Specificity No disease if the factor isn’t present Biological Plausibility Fits the natural history of the disease

15. Common Pitfalls What is bias?

16. Common Pitfalls What is bias? An event that produces deviations that shift data in a particular direction (skew your data)

17. Common Pitfalls What is bias? An event that produces deviations that shift data in a particular direction (skew your data) Common Types

18. Common Pitfalls What is bias? An event that produces deviations that shift data in a particular direction (skew your data) Common Types Assembly bias – characteristics of a group are not evenly distributed

19. Common Pitfalls What is bias? An event that produces deviations that shift data in a particular direction (skew your data) Common Types Assembly bias – characteristics of a group are not evenly distributed Selection bias – participants allowed to select which part of the study they are in

20. Common Pitfalls What is bias? An event that produces deviations that shift data in a particular direction (skew your data) Common Types Assembly bias – characteristics of a group are not evenly distributed Selection bias – participants allowed to select which part of the study they are in Detection bias – failure to detect true cause of disease

21. Common Pitfalls What is bias? An event that produces deviations that shift data in a particular direction (skew your data) Common Types Assembly bias – characteristics of a group are not evenly distributed Selection bias – participants allowed to select which part of the study they are in Detection bias – failure to detect true cause of disease Measurement bias –variations due to instrumentation or user error

22. Common Pitfalls Additional concerns when doing research…?

23. Common Pitfalls Additional concerns when doing research…? Random error

24. Common Pitfalls Additional concerns when doing research…? Random error Confounding

25. Common Pitfalls Additional concerns when doing research…? Random error Confounding Synergism

26. Research Design All research is descriptive, and results are directly related to the data assembled

27. Research Design All research is descriptive, and results are directly related to the data assembled What is a hypothesis ?

28. Research Design All research is descriptive, and results are directly related to the data assembled What is a hypothesis ? An “educated guess” about the relationship that exists in an observed phenomenon

29. Research Design All research is descriptive, and results are directly related to the data assembled What is a hypothesis ? An “educated guess” about the relationship that exists in an observed phenomenon Not always right; often need to re-test to truly discern relationship

30. Research Design All research is descriptive, and results are directly related to the data assembled What is a hypothesis ? An “educated guess” about the relationship that exists in an observed phenomenon Not always right; often need to re-test to truly discern relationship It’s called RE-SEARCH for a reason ! : )

31. Research Design 4 Key Factors of Research Designs

32. Research Design 4 Key Factors of Research Designs Enable comparison of a variable for two or more groups at a specified time

33. Research Design 4 Key Factors of Research Designs Enable comparison of a variable for two or more groups at a specified time Comparison must be quantified in absolute or relative terms

34. Research Design 4 Key Factors of Research Designs Enable comparison of a variable for two or more groups at a specified time Comparison must be quantified in absolute or relative terms Allow determination of the temporal sequence (when and how the factor and disease occur)

35. Research Design 4 Key Factors of Research Designs Enable comparison of a variable for two or more groups at a specified time Comparison must be quantified in absolute or relative terms Allow determination of the temporal sequence (when and how the factor and disease occur) Minimize bias, confounding, and other outside elements that may skew from true results

36. Research Designs Designs for Generating Hypotheses

37. Research Designs Designs for Generating Hypotheses Cross-Sectional Surveys

38. Research Designs Designs for Generating Hypotheses Cross-Sectional Surveys Quick, cost-effective studies done of a population at a certain point in time (calls, interviews, appointments, etc)

39. Research Designs Designs for Generating Hypotheses Cross-Sectional Surveys Quick, cost-effective studies done of a population at a certain point in time (calls, interviews, appointments, etc) Useful in determining prevalent risk factors in a population

40. Research Designs Designs for Generating Hypotheses Cross-Sectional Surveys Quick, cost-effective studies done of a population at a certain point in time (calls, interviews, appointments, etc) Useful in determining prevalent risk factors in a population Surveys sometimes have low response rates

41. Research Designs Designs for Generating Hypotheses Cross-Sectional Ecological Studies

42. Research Designs Designs for Generating Hypotheses Cross-Sectional Ecological Studies Relate the frequency of one characteristic (smoking) and an outcome (lung cancer) occurring in a geographical area

43. Research Designs Designs for Generating Hypotheses Cross-Sectional Ecological Studies Relate the frequency of one characteristic (smoking) and an outcome (lung cancer) occurring in a geographical area Downside is too many other factors and temporal issues may be overlooked or incorrectly identified

44. Research Designs Designs for Generating Hypotheses Cross-Sectional Ecological Studies Relate the frequency of one characteristic (smoking) and an outcome (lung cancer) occurring in a geographical area Downside is too many other factors and temporal issues may be overlooked or incorrectly identified Longitudinal Ecological Studies

45. Research Designs Designs for Generating Hypotheses Cross-Sectional Ecological Studies Relate the frequency of one characteristic (smoking) and an outcome (lung cancer) occurring in a geographical area Downside is too many other factors and temporal issues may be overlooked or incorrectly identified Longitudinal Ecological Studies Long-term surveillance or frequent cross-sectional surveys to measure trends in disease rates over many years

46. Research Designs Designs for Generating or Testing Hypotheses

47. Research Designs Designs for Generating or Testing Hypotheses Cohort Studies

48. Research Designs Designs for Generating or Testing Hypotheses Cohort Studies Compares two groups of clearly defined individuals, randomly selected

49. Research Designs Designs for Generating or Testing Hypotheses Cohort Studies Compares two groups of clearly defined individuals, randomly selected Observations made to examine if one group develops a condition with a risk factor, the other without

50. Research Designs Designs for Generating or Testing Hypotheses Prospective vs. Retrospective Cohort Studies

51. Research Designs Designs for Generating or Testing Hypotheses Prospective vs. Retrospective Cohort Studies Prospective cohorts are done at present time, baseline data recorded and then observed over time

52. Research Designs Designs for Generating or Testing Hypotheses Prospective vs. Retrospective Cohort Studies Prospective cohorts are done at present time, baseline data recorded and then observed over time Retrospective cohorts look back in time to a risk group and follow members in a current day scenario to see what conditions are now prevalent

53. Research Designs Designs for Generating or Testing Hypotheses Prospective vs. Retrospective Cohort Studies Prospective cohorts are done at present time, baseline data recorded and then observed over time Advantages are control of standardized procedures and diagnosis, estimates of risk generated are true, many different disease outcomes may be studied at once Disadvantages are high costs, loss of follow-up, long wait for final results Retrospective cohorts look back in time to a risk group and follow members in a current day scenario to see what conditions are now prevalent

54. Research Designs Designs for Generating or Testing Hypotheses Prospective vs. Retrospective Cohort Studies Prospective cohorts are done at present time, baseline data recorded and then observed over time Advantages are control of standardized procedures and diagnosis, estimates of risk generated are true, many different disease outcomes may be studied at once Disadvantages are high costs, loss of follow-up, long wait for final results Retrospective cohorts look back in time to a risk group and follow members in a current day scenario to see what conditions are now prevalent Good to estimate absolute risk, but lacks ability to control data collection and standardization

55. Research Designs Designs for Testing Hypotheses

56. Research Designs Designs for Testing Hypotheses Randomized Controlled Clinical Trials (RCCT)

57. Research Designs Designs for Testing Hypotheses Randomized Controlled Clinical Trials (RCCT) Patients placed into two groups, one receiving a treatment the other a placebo (usually a therapeutic treatment) Use of “blinding” in trials ?

58. Research Designs Designs for Testing Hypotheses Randomized Controlled Clinical Trials (RCCT) Patients placed into two groups, one receiving a treatment the other a placebo (usually a therapeutic treatment) Use of “blinding” in trials ? Patients are unaware of which group they are in (single), those dosing the patients also do not know (double) Key is that both groups must be treated equally

59. Research Designs Designs for Testing Hypotheses Randomized Controlled Clinical Trials (RCCT) Patients placed into two groups, one receiving a treatment the other a placebo (usually a therapeutic treatment) Use of “blinding” in trials ? Patients are unaware of which group they are in (single), those dosing the patients also do not know (double) Key is that both groups must be treated equally Randomized Controlled Field Trials (RCFT)

60. Research Designs Designs for Testing Hypotheses Randomized Controlled Clinical Trials (RCCT) Patients placed into two groups, one receiving a treatment the other a placebo (usually a therapeutic treatment) Use of “blinding” in trials ? Patients are unaware of which group they are in (single), those dosing the patients also do not know (double) Key is that both groups must be treated equally Randomized Controlled Field Trials (RCFT) Focuses on using a preventative measure, rather than a therapeutical one (RCCT)

61. Well Done!!