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Backpacks and Back Pain

Backpacks and Back Pain. Is there an association between the hypothesized cause and the disease?. Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain. Hypotheses. 1 How is this disease distributed?. 2

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Backpacks and Back Pain

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  1. Backpacks and Back Pain Is there an association between the hypothesized cause and the disease? Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  2. Hypotheses 1 How is this disease distributed? 2 Is there an association? Did the exposure and the disease turn up together? 3 Is the association causal? 4 What should be done to prevent the disease? 5 Did the prevention strategy work? Where are we and where are we going? What’s my hypothesis? Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  3. Review Under what circumstances is it appropriate to experiment with human beings? How can we test a hypothesis that something causes harm in a human experiment? How can we test the hypothesis that carrying a heavy backpack causes back pain in a way that follows the principles you developed in the previous investigation? Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  4. Carrying Heavy Backpacks Causes Back Pain. Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  5. Epi Talk Epi Talk Natural Experiment Naturally occurring circumstances in which groups of people within a population have been exposed to different levels of the hypothesized cause of an outcome. Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  6. Epi Talk Epi Talk Observational Studies Epidemiologic studies of natural experiments in which the investigator is not involved in the intervention other than to record, classify, count, and statistically analyze results. Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  7. Epi Talk Epi Talk Trial An epidemiologic experiment in which subjects are assigned into groups to receive or not receive a hypothesized beneficial intervention. Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  8. Epi Talk Epi Talk Experimental Group Subjects selected for a trial who are assigned to a group to receive a hypothesized beneficial intervention. Detectives in the Classroom - Investigation 2-4: Backpacks And Back Pain Investigation 2-4

  9. Smoke Do Not Smoke Trial Hypothesis: Cigarette smoking causes lung cancer. Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  10. Smoke Do Not Smoke Trial Hypothesis: Cigarette smoking causes lung cancer. Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  11. Testing Hypotheses Ache! Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  12. Testing Hypotheses Control Group Relative Risk Inferences 2 X 2 Table Risks Belmont Report Carrying heavy backpacks causes back pain. Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  13. Trial No Acne Acne Total AcneMed 100 a b c d No AcneMed 100 Carrying heavy backpacks causes back pain. Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  14. No Back Pain Back Pain Heavy Backpacks a b c d No Heavy Backpacks Observational Study Total Carrying heavy backpacks causes back pain. Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  15. ? 100 ? 100 There are no 100’s in the “Total” column. Testing Hypotheses No Back Pain No Acne Back Pain Total Acne Total Heavy Backpack AcneMed 100 a b a b c d c d No Heavy Backpack No AcneMed 100 Observational Study Trial What is the difference? Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  16. “Heavy” Carry No More Than 15% of Your Body Weight Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  17. 120 lbs 15 % What is 15% of someone’s body weight? What is 15% of 120 lbs? 18 lbs 120 X .15 = Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  18. 20 lbs Heavy 15% of Maria’s body weight = 18 lbs Is Maria’s backpack heavy? Yes Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  19. Epi Log Worksheet Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  20. 1 Exposure Check one. Heavy Backpack No Heavy Backpack Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  21. Outcome What is back pain? Any memorable pain in the past two weeks. Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  22. 2 Outcome Check one. Back Pain No Back Pain Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  23. No Back Pain Back Pain Heavy Backpacks No Heavy Backpacks 2 x 2 Table Total a b c d Can you think of someone, anyone, anywhere in the whole wide world, who could not “fit” into cell a, b, c, or d? Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  24. Investigation 2-4 Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  25. Epi Talk Epi Talk Informed Consent Voluntary consent given by a person for participation in a study. Participants must know and understand the study, give consent without coercion, and know that they can withdraw at any time. Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  26. Investigation 2-4 Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  27. No Back Pain Back Pain Heavy Backpacks No Heavy Backpacks 2 x 2 Table Total      a b c d     Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  28. 3 2x2 Table No Back Pain Back Pain Total Heavy Backpacks a b c d No Heavy Backpacks Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  29. 4 Risk No Back Pain Back Pain Risks Back Pain Total Heavy Backpacks % or a b c d No Heavy Backpacks % or Numerator is the number of people who have back pain and denominator is the number of people in the population. Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  30. 5 Relative Risk No Back Pain Back Pain Risks Relative Risk Back Pain Total Heavy Backpacks % or a b c d No Heavy Backpacks % or Divide the risk of the outcome in the exposed group by the risk of the outcome in the unexposed group. Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  31. 6 Relative Risk No Back Pain Back Pain Risks Relative Risk Back Pain Total Heavy Backpacks % or a b c d No Heavy Backpacks % or Students who carried heavy backpacks were ______ times as likely to have back pain as students who did not carry heavy backpacks. Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  32. 7 Inference No Back Pain Back Pain Risks Relative Risk Back Pain Total Heavy Backpacks % or a b c d No Heavy Backpacks % or Predict from what is observed to what is not observed. Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  33. Carrying Heavy Backpacks Causes Back Pain. Trial Heavy Backpacks No Heavy Backpacks Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  34. Carrying Heavy Backpacks Causes Back Pain. Observational Study Heavy Backpacks No Heavy Backpacks Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  35. Carrying Heavy Backpacks Causes Back Pain. How could the hypothesis be tested in a trial? What “principles” would be broken in a trial? Was the same “principle” broken in the observational study? Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  36. 8 Review Were you involved in assigning exposures? Epi Talk Observational Studies Epidemiologic studies of natural experiments in which the investigator is not involved in the intervention other than to record, classify, count, and statistically analyze results. Did you observe what others had done to themselves? Did you record, classify, count and statistically analyze the results? Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  37. Carrying Heavy Backpacks Causes Back Pain. Trial Heavy Backpacks No Heavy Backpacks Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  38. Carrying Heavy Backpacks Causes Back Pain. Observational Study Heavy Backpacks No Heavy Backpacks Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  39. Trial Carrying Heavy Backpacks Causes Back Pain. Heavy Backpacks No Heavy Backpacks Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  40. Carrying Heavy Backpacks Causes Back Pain. We are all carrying out “natural experiments” on ourselves each day of our lives, as we decide what to do, where to go, and to what to expose ourselves. Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

  41. CDC Backpacks and Back Pain Investigation 2-4 has ended. Detectives in the Classroom - Investigation 2-4: Backpacks and Back Pain Investigation 2-4

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