2. Epidemiology Kept Simple Chapter 1 Epidemiology Past & Present

3. Comments re: Text EKS = Epidemiology Kept Simple EKS = Epidemiology Kept Simple 20 chapters 20 chapters We cover about 8We cover about 8 Multiple sections (§) per chapter Multiple sections (§) per chapter We do not cover all sections in chaptersWe do not cover all sections in chapters Chapter outline on first page Chapter outline on first page To help organize thinkingTo help organize thinking

4. §1.1 Epidemiology, Health, and Public Health What is Epidemiology?What is Epidemiology? What is Public Health?What is Public Health? What is Health?What is Health?

5. Epidemiology Defined Greek rootsGreek roots epi = uponepi = upon demos = the peopledemos = the people ology = study ofology = study of Literally - “study of epidemics”Literally - “study of epidemics” Modern definitions include references toModern definitions include references to distributions of health determinant (statistical concept)distributions of health determinant (statistical concept) determinants of disease (pathophysiologic concept)determinants of disease (pathophysiologic concept) application in control of health problems (biological and social concepts)application in control of health problems (biological and social concepts)

6. Comparison of epi annd medicine Main unit of concernMain unit of concern Epi –- populationEpi –- population Medicine -- individualMedicine -- individual But …But … Epi becoming more medical over timeEpi becoming more medical over time Medicine becoming more epidemiologic over timeMedicine becoming more epidemiologic over time

7. Public Health Definitions include reference toDefinitions include reference to organized effort (“activity”)organized effort (“activity”) reduction of morbidity / mortality and improved healthreduction of morbidity / mortality and improved health Composed of dozens of disciplinesComposed of dozens of disciplines e.g., microbiology, psychology, administration, epidemiology, health ed., etc.e.g., microbiology, psychology, administration, epidemiology, health ed., etc. Has been called “undisciplined”Has been called “undisciplined” Comparison of epi and public healthComparison of epi and public health epi = “a study of”epi = “a study of” pub health = “an activity”pub health = “an activity” Follow-up on WebCT discussion board?Follow-up on WebCT discussion board?

8. Health Multiple definitions (cultural specific?)Multiple definitions (cultural specific?) WHO (1948) defined health as “well-being”WHO (1948) defined health as “well-being” Not merely the absence of diseaseNot merely the absence of disease Physical, mental, and social well-beingPhysical, mental, and social well-being Should definitions of health reference quality of life?Should definitions of health reference quality of life? ProsPros ConsCons

9. Additional Terms Morbidity = disease or disabilityMorbidity = disease or disability Mortality = deathMortality = death Occurrence of disease = prevalence or incidence (will distinguish later in course)Occurrence of disease = prevalence or incidence (will distinguish later in course) Endemic = normal occurrenceEndemic = normal occurrence Epidemic = greater than normal occurrenceEpidemic = greater than normal occurrence Pandemic = epidemic on multiple continentsPandemic = epidemic on multiple continents

10. §1.2 Uses of Epi (Morris, 1957) see pp. 3 - 4 1.Historical study 2.Community diagnosis 3.Working of health services 4.Individual chances 5.Complete clinical picture 6.Identify new syndromes 7.Determine cause (ultimate importance)

11. §1.3 Epidemiologic Transition (pp. 4 – 10) This section of the text has section headings:This section of the text has section headings: 20 th century changes in disease patterns20 th century changes in disease patterns Mortality trends since 1950Mortality trends since 1950 Life expectancyLife expectancy Intends to provide additional contextIntends to provide additional context

12. Leading Causes of Death 19001990 1 Pneumonia / influenza Heart disease 2TBNeoplasms 3DiarrheaCerbrovascular 4 Heart disease* COPD 5Cerebrovascular* Pneumonia/ influenza * Large % had infectious component

13. Changes in mortality Epi transitionEpi transition Acute to chronic causeAcute to chronic cause Infectious to “life style” causeInfectious to “life style” cause Decrease mortality overallDecrease mortality overall Death burden shifted to older agesDeath burden shifted to older ages Many causesMany causes Medical technology (antibiotics, anesthesia)Medical technology (antibiotics, anesthesia) Birth controlBirth control NutritionNutrition Sanitation and vector controlSanitation and vector control EducationEducation Improved standard of livingImproved standard of living etc. (don’t over-simplify!)etc. (don’t over-simplify!)

14. Demographic Transition

15. U. S. Mortality 1950 – 1990 Discuss (Fig 1.2, p. 8)

16. Mortality, Selected Cancer, U. S. (Fig. 1.3, p. 9)

17. Life Expectancy at Birth (Fig. 1.4, p. 10)

18. §1.4 Selected Historical Figures and Events “An essential part of the outfit of the investigator in the field” (Major Greenwood)“An essential part of the outfit of the investigator in the field” (Major Greenwood) Headings in this sectionHeadings in this section Before epi was a separate disciplineBefore epi was a separate discipline Emergence of epi in Victorian EnglandEmergence of epi in Victorian England Twentieth century epiTwentieth century epi Smallpox (optional)Smallpox (optional)

19. Before Epi was a Discipline pp. 11 – 12 We must understand the role of culture and western civilizationWe must understand the role of culture and western civilization Selected points:Selected points: Pre-scientific medicine was based on philosophy, religion, and moralityPre-scientific medicine was based on philosophy, religion, and morality Hippocrates symbolizes the shift to observation and the environmentHippocrates symbolizes the shift to observation and the environment The Dark Ages represent a decline in enlightenment and public healthThe Dark Ages represent a decline in enlightenment and public health The Protestant reformation brought with it important cultural changesThe Protestant reformation brought with it important cultural changes

20. Western Civilization and Scientific Revolution (cont.) Western Civilization and Scientific Revolution (cont.) The renaissance brought with it an Age of EnlightenmentThe renaissance brought with it an Age of Enlightenment Science liberates itself from philosophy, morality, and religionScience liberates itself from philosophy, morality, and religion Post-modernism risks decadencePost-modernism risks decadence

21. Demographic Approach John Graunt (1620 – 1674)John Graunt (1620 – 1674) pp. 12 – 14pp. 12 – 14

22. Graunt’s Life Table % surviving to age 664 1640 2625 3616 4610 566 603 761 800

23. Lessons Learned from Graunt (Rothman, 1996) he was briefhe was brief made reasoning clearmade reasoning clear subjected theories to multiple and varied testssubjected theories to multiple and varied tests invited criticisminvited criticism was willing to change ideas when confronted with contradictory evidencewas willing to change ideas when confronted with contradictory evidence avoided mechanical interpretationsavoided mechanical interpretations

24. Germ Theory (p. 14) HighlightsHighlights Self-replicating (i.e., biological) agentSelf-replicating (i.e., biological) agent Theory not accepted until late 1800sTheory not accepted until late 1800s Competing theory (“miasma” = atmospheric pollution) was accepted as late 1880sCompeting theory (“miasma” = atmospheric pollution) was accepted as late 1880s Early contagionistsEarly contagionists Fracastoro (first cogent germ theory, 16 th century)Fracastoro (first cogent germ theory, 16 th century) Jakob Henle & Robert KochJakob Henle & Robert Koch PasteurPasteur Snow (see next section)Snow (see next section) Salmon (vector borne transmission)Salmon (vector borne transmission)

25. John Snow Quintessential epidemiologic heroQuintessential epidemiologic hero Physiologist, anesthesiologist, & epidemiologistPhysiologist, anesthesiologist, & epidemiologist Remembered forRemembered for Insightful theory of diseaseInsightful theory of disease Impressive methods of studiesImpressive methods of studies

26. Snow’s Waterborne Theory Refuted miasma in favor of contagionRefuted miasma in favor of contagion Theory onTheory on Clinical facts: symptoms and treatmentClinical facts: symptoms and treatment Physiologic understanding: death due to fluid loss, smudging of blood, and asphyxiationPhysiologic understanding: death due to fluid loss, smudging of blood, and asphyxiation Epidemiologic observations: epidemics followed routes of commerce, environmental contamination during epidemicsEpidemiologic observations: epidemics followed routes of commerce, environmental contamination during epidemics

27. Components of Snow’s Contagion Theory Free-living agentFree-living agent Fecal-oral transmission (person-to-person)Fecal-oral transmission (person-to-person) Agent multiplies within the hostAgent multiplies within the host Water-borne transmissionWater-borne transmission to age 16

28. Snow’s Methods Snow’s methods are a model for non- experimental epiSnow’s methods are a model for non- experimental epi Three types of studiesThree types of studies Ecological design: compared cholera rates by regionEcological design: compared cholera rates by region Cohort design: compared cholera rates in exposed and non-exposed individualsCohort design: compared cholera rates in exposed and non-exposed individuals Case-control design: compared exposure status in those with and without diseaseCase-control design: compared exposure status in those with and without disease

29. Snow’s Ecological Study Figure 1.13 (p. 24)

30. Ecological Study Key data in Figure 1.13 (p. 24) Example of rate calculationExample of rate calculation Rate St. Saviour = 45 / 19,709 × 100,000 = 227Rate St. Saviour = 45 / 19,709 × 100,000 = 227 Rate Christchurch = 7 / 16,022 × 100,000 = 43Rate Christchurch = 7 / 16,022 × 100,000 = 43 Water sourceWater source St. Saviour – Southwark and Vauxhall Water OnlySt. Saviour – Southwark and Vauxhall Water Only Christchurch – multiple water companies including Vauxhall Christchurch – multiple water companies including Vauxhall

31. Snow’s Cohort Study Key data in Table 1.7 (p. 25) Data by householdData by household Household water sources knownHousehold water sources known Rates per 10,000 households = cases / households × 10,000Rates per 10,000 households = cases / households × 10,000 Main comparison:Main comparison: Rate Southwark & Vauxhall = 1263 / 40,046 × 10,000 = 315Rate Southwark & Vauxhall = 1263 / 40,046 × 10,000 = 315 Rate Lambeth = 98 / 26107 × 10,000 = 37.5Rate Lambeth = 98 / 26107 × 10,000 = 37.5 Conclude: Southwark & Vauxhall households had 8.5 time risk of LambethConclude: Southwark & Vauxhall households had 8.5 time risk of Lambeth

32. Snow’s Case-Control Study Collect data on all casesCollect data on all cases Determine source of water for cases and non-casesDetermine source of water for cases and non-cases See pp. 23 – 26 for examples of interviewsSee pp. 23 – 26 for examples of interviews

33. Snow’s Map of Golden Square Cholera Outbreak (Fig 1.14) Cases more likely to live near Broad St. pumpCases more likely to live near Broad St. pump Exceptions: no cases in Brewery and few cases in WorkhouseExceptions: no cases in Brewery and few cases in Workhouse {Paste section of map here}{Paste section of map here}

34. Exposure to Broad St. Pump Water Case-control studies measure frequency of exposure (not frequency of disease)Case-control studies measure frequency of exposure (not frequency of disease) Consumption (exposure) frequent in casesConsumption (exposure) frequent in cases 61 cases – exposure confirmed61 cases – exposure confirmed 6 cases – non-exposed6 cases – non-exposed 6 cases – equivocal6 cases – equivocal Exposure rare in non-casesExposure rare in non-cases Exposure more frequent in cases than controlsExposure more frequent in cases than controls

35. Removal of Broad Street Pump Handle Snow supported his [good] theory with high quality dataSnow supported his [good] theory with high quality data But how did he convince the Guardians of the Golden Square area to remove the pump handle?But how did he convince the Guardians of the Golden Square area to remove the pump handle?

36. 20 th Century Epidemiology (p. 26) Addressing the chronic disease associated with epidemiologic TransitionAddressing the chronic disease associated with epidemiologic Transition Illustrative examplesIllustrative examples British Doctors Study (Doll & Hills studies of the effects of smoking)British Doctors Study (Doll & Hills studies of the effects of smoking) Framingham Heart Study (risk factors for heart disease, many investigators)Framingham Heart Study (risk factors for heart disease, many investigators)