Terminology

1. Terminology Scientific Epidemiological Statistical

2. Scientific terminology • Empirical Fact • Obvious observation from experiment • Empirical observation – a process of gathering information by direct observation • Evidence is said to be empirical if it is based on observations and measurements of reality Evidence-based Chiropractic

3. Terminology (cont.) • Empirical research is: • Research which is based on observed and measured phenomena and • Is research that derives knowledge from actual experience rather than from theory or belief Evidence-based Chiropractic

4. Terminology (cont.) • Assumption • A fact or statement taken for granted • Accepted as true based on logic, without proof • Hypothesis • An educated prediction of the outcome of an experiment Evidence-based Chiropractic

5. Terminology (cont.) • Law • Principles that are taken to be universally applicable • Newton’s laws of motion • Boyle’s law • A statement of fact detailing a sequence or relation of phenomena that is invariable under given conditions (Stedman’s Medical Dictionary) Evidence-based Chiropractic

6. Terminology (cont.) • Theory • An explanation for some phenomenon which is based on observation, experimentation, and reasoning • Hypothesis that is well confirmed or established • Cause • Something that makes an event happen • Science is often interested in looking at cause-effect relationships Evidence-based Chiropractic

7. Theory vs. hypothesis • A theory is an explanation • The validity of a theory depends on its ability to explain phenomena • Theories may be supported, rejected, or modified based on new evidence • A hypothesis is a testable idea • Scientists do not set out to “prove” hypotheses, but to test them • Often multiple hypotheses are posed to explain phenomena; the goal of research is to eliminate those that are incorrect Evidence-based Chiropractic

8. Terminology (cont.) • Objectivity • Scientists are responsible for putting aside their biases and beliefs and seeing the world as it “really is” • No one is ever perfectly objective • Some scientists are less objective than others, which is one reason we have to critically evaluate research Evidence-based Chiropractic

9. Scientific method • The principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation . . . The American Heritage dictionary of the English language. 4th ed. 2000, Boston: Houghton Mifflin. xxxvii, 2074 p. Evidence-based Chiropractic

10. Scientific method cont. • Generally involving: • The observation of phenomena • The formulation of a hypothesis concerning the phenomena • Experimentation to demonstrate the truth or falseness of the hypothesis • A conclusion that validates or modifies the hypothesis Evidence-based Chiropractic

11. Cause as risk factor • A cause is a factor (or member of a set of factors) which results in a sequence of events that eventually result in an outcome Exposure  Outcome Cause  Effect Evidence-based Chiropractic

12. Causation • Causation is investigated by determining an association between exposure and outcome • e.g., Smoking and lung cancer or Chiropractic care and optimal health • Study of causation leads to inference • From statistical sample data to generalizations (to a target population) usually with calculated degrees of certainty (95%) Evidence-based Chiropractic

13. Establishing cause Temporal Precedence then Cause Effect Time Why this is important Cyclical Functions Pain levels Time Evidence-based Chiropractic

14. Theory • A reasoned explanation of known facts or phenomena that serves as a basis of investigation by which to seek the truthStedman’s Evidence-based Chiropractic

15. The building blocks of Theory • Concepts • Conceptual definitionsare abstract • Ideas for research • Operational definitions • Operational definitions are concrete • Deduced from conceptual definitions • Propositions • Statements of relationships among concepts Evidence-based Chiropractic

16. Concepts • Abstractions that allow classification of observations • When scalar values can be assigned, they may become variables • Variables must be operationallydefined Evidence-based Chiropractic

17. Operational definitions • Description and explanation of the exact procedures for measuring or observing the phenomenon, event, or behavior Evidence-based Chiropractic

18. Propositions • Propositions state the nature of the relationship between variables (concepts) • Hypotheses are derived from propositions • An hypothesis is a statement about the expected relationship between two or more concepts that is based on a theory and that can be tested Evidence-based Chiropractic

19. Chiropractic Concepts • Variables: • Adjustment • Subluxation • Health Evidence-based Chiropractic

20. Chiropractic Propositions • Between subluxation and health Subluxation Health • Between adjustment andsubluxation Adjustment Subluxation • Between adjustment and health Adjustment Health Evidence-based Chiropractic

21. Epidemiology • Epidemiology • The science concerned with the patterns of disease frequency in human populations • Distribution of disease by person, place, time • Assumptions: • Disease does not occur randomly • Disease has identifiable causes which can be altered and thus prevent it from developing Evidence-based Chiropractic

22. DefinitionofEpidemiology • The study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to control health problems. Dictionary of Epidemiology Evidence-based Chiropractic

23. Dr. John Snow the father of epidemiology • Dr. Snow lived in London during a severe cholera epidemic • The medical establishment thought cholera was spread by miasmas (bad air from decayed organic matter) • But Dr. Snow theorized that it was spread by contaminated water Evidence-based Chiropractic

24. The father of epidemiology (cont.) • He surveyed the houses near a certain public water pump and discovered that nearly all persons who died had consumed water from that pump • He presented his data to the local authorities who immediately had the pump handle removed • The outbreak quickly subsided as a result Evidence-based Chiropractic

25. The father of epidemiology (cont.) • His theory continued to be rejected by his peers until Vibrio cholerae was eventually identified as the cause of the disease • However, the statistical and mapping methods used during the investigation formed the foundation of epidemiology Evidence-based Chiropractic

26. Dr. Snow’s map Evidence-based Chiropractic

27. Close-up of Dr. Snow’s map Broad street pump Deaths Evidence-based Chiropractic

28. Measurement of disease frequency and occurrence • Incidence • The probability of a person being diagnosed with a disease during a specific period of time (typically one year) • The number of newly diagnosed cases of a disease during a specified time period Evidence-based Chiropractic

29. Incidence (cont.) • For example, a study of 1,000 bus drivers found 50 new cases of low back pain in one year • The incidence is 50/1,000 = 0.05 or 5,000 per 100,000 • Some workers may have had more than 1 episode of low back pain during the year, but only the first occurrence is usually counted Evidence-based Chiropractic

30. Risk • An estimate of the proportion of unaffected persons in a population who will develop the disease of interest over a specified period of time • Estimated by observing a population that is at risk over a defined period of time to determine the number of new cases as compared with the total number of persons Evidence-based Chiropractic

31. Prevalence • The proportion of persons in a given population that have a disease at a certain point in time • The total number of cases of the disease in that population • It does not matter when they were diagnosed with the condition Evidence-based Chiropractic

32. Prevalence (cont.) • For example, a study of community with a population of 30,000 which found 1,000 persons with migraine headaches • The prevalence is 1,000/30,000 = 0.033 or 3,300 per 100,000 persons • It doesn’t matter that 200 of the cases were newly diagnosed and 800 already had migraine headaches when the study began Evidence-based Chiropractic

33. Point prevalence • The proportion of a population with a disease at a given point in time • May underestimate the frequency of certain conditions Evidence-based Chiropractic

34. Period prevalence • The proportion of a population that has a disease within a defined period of time • Involves repeated monitoring of a population • Thus is a better depiction of the overall frequency of a disease Evidence-based Chiropractic

35. Incidence and prevalence • Sometimes reported as a percentage • For example • Manchikanti et al studied 500 consecutive chronic spine pain patients and reported the prevalence of facet joint pain as 55% in the cervical, 42% in the thoracic, and 31% in the lumbar spine Evidence-based Chiropractic

36. Incidence and prevalence (cont.) • Prevalence is usually much lower than incidence in short duration diseases (e.g., the common cold) • Many people contract colds each year, but relatively few people have a cold at one time because the duration is so short Evidence-based Chiropractic

37. Incidence and prevalence (cont.) • Prevalence in chronic conditions is higher than its incidence (e.g., diabetes) • There are 1.2 million new cases of diabetes each year, but once diagnosed, the condition remains and each year’s incidence is added to the overall prevalence, minus those who die having the condition = 18.2 million Evidence-based Chiropractic

38. Prevalence and incidence illustrated Evidence-based Chiropractic

39. Case begins Case ends Evidence-based Chiropractic

40. Causation in epidemiology • In order to determine whether exposure to a specific risk factor actually caused a particular disease within a population, three key criteria should be met • Temporality • Consistency • Dose-response Evidence-based Chiropractic

41. Temporalitya.k.a., temporal precedence • The exposure must occur prior to the onset of a disease • However, just because a given exposure precedes a given disease, does not necessarily mean there is a cause-and-effect relationship • Alternate explanations are possible Evidence-based Chiropractic

42. Temporality (cont.) • Four possible interpretations of temporal relationships • Event A caused event B • Event B caused event A • Both events A and B were caused by a third related event • Neither A or B are related to each other or a third event, but the temporal relationship was merely by chance Evidence-based Chiropractic

43. Consistency • Studies on the relationship carried out by other researchers using different populations get similar results • A large number of good quality observational studies reporting consistent results are required in order to conclude that A caused B Evidence-based Chiropractic

44. Dose-response • When greater exposure to a risk factor results in a greater effect on health • For example, the more cigarettes a person smokes per day (the dose), the more likely they are to develop lung cancer (the response) Evidence-based Chiropractic

45. Bradford Hill’s criteria for causation • Six additional criteria used to identify cause-and-effect relationships • Keep in mind, none of these criteria can bring indisputable evidence for or against a cause and effect relationship Evidence-based Chiropractic

46. Bradford Hill’s Criteria of Causation • Strength of association – The stronger the relation between the risk and the outcome is, the less likely it was caused by other factors • Consistency – The replication of study results by different researchers in a different setting • Specificity in the cause – The exposure should be associated with a single specific disease • Temporality – The exposure must precede the disease • Dose response relationship – Increased exposures should correspond to increased risk of disease • Plausibility – There should be a rational scientific basis for the association risk of disease • Coherence – The association must be consistent with other knowledge on the topic • Experimental evidence – Research that is based on experiments reinforces a causal inference • Analogy – The association is analogous to a known causal relationship Evidence-based Chiropractic

47. Bradford Hill Criteria (cont.) • Were developed for use in the field of occupational medicine, but  have been widely applied in other fields • Criteria serve as a general guide, and are not meant to be an inflexible list • Findings of experimental research is preferred, but oftentimes research questions and variables do not lend themselves to rigorous investigation Evidence-based Chiropractic

48. Cagnie B, et al. Changes In Cerebellar Blood Flow After Manipulation of The Cervical Spine Using Technetium 99m–Ethyl Cysteinate Dimer. J Manipulative Physiol Ther 2005;28:103- 107. Evidence-based Chiropractic

49. Bradford Hill (cont.) • When using them, don’t forget Hill’s advice: • “None of these nine viewpoints can bring indisputable evidence for or against a cause and effect hypothesis …. What they can do, with greater or less strength, is to help answer the fundamental question—is there any other way of explaining the set of facts before us, is there any other answer equally, or more likely, than cause and effect?” (Cited in Doll, 1991) Evidence-based Chiropractic

50. Smoking causes lung cancer • Where is the RCT that gave evidence to this? • Decades of observational research • Observing the same thing in a wide variety of settings • Some free of some types of bias, others free of other types of bias Evidence-based Chiropractic