Epidemiology Kept Simple Chapter 1 Epidemiology Past & Present.

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  • Epidemiology Kept SimpleChapter 1Epidemiology Past & Present

  • Comments re: Text EKS = Epidemiology Kept Simple 20 chapters We cover about 8Multiple sections () per chapterWe do not cover all sections in chaptersChapter outline on first pageTo help organize thinking

  • 1.1 Epidemiology, Health, and Public HealthWhat is Epidemiology?What is Public Health?What is Health?

  • Epidemiology DefinedGreek rootsepi = upondemos = the peopleology = study of Literally - study of epidemicsModern definitions include references to distributions of health determinant (statistical concept)determinants of disease (pathophysiologic concept)application in control of health problems (biological and social concepts)

  • Comparison of epi annd medicineMain unit of concernEpi - populationMedicine -- individualBut Epi becoming more medical over timeMedicine becoming more epidemiologic over time

  • Public HealthDefinitions include reference to organized effort (activity)reduction of morbidity / mortality and improved healthComposed of dozens of disciplinese.g., microbiology, psychology, administration, epidemiology, health ed., etc. Has been called undisciplined Comparison of epi and public healthepi = a study ofpub health = an activityFollow-up on WebCT discussion board?

  • HealthMultiple definitions (cultural specific?)WHO (1948) defined health as well-being Not merely the absence of diseasePhysical, mental, and social well-beingShould definitions of health reference quality of life?ProsCons

  • Additional TermsMorbidity = disease or disabilityMortality = death Occurrence of disease = prevalence or incidence (will distinguish later in course)Endemic = normal occurrenceEpidemic = greater than normal occurrencePandemic = epidemic on multiple continents

  • 1.2 Uses of Epi (Morris, 1957)see pp. 3 - 4Historical studyCommunity diagnosisWorking of health servicesIndividual chancesComplete clinical pictureIdentify new syndromesDetermine cause (ultimate importance)

  • 1.3 Epidemiologic Transition(pp. 4 10)This section of the text has section headings:20th century changes in disease patternsMortality trends since 1950 Life expectancyIntends to provide additional context

  • Leading Causes of Death * Large % had infectious component

    190019901Pneumonia / influenzaHeart disease2TBNeoplasms3DiarrheaCerbrovascular4Heart disease* COPD5Cerebrovascular*Pneumonia/ influenza

  • Changes in mortalityEpi transitionAcute to chronic causeInfectious to life style causeDecrease mortality overall Death burden shifted to older agesMany causes Medical technology (antibiotics, anesthesia)Birth controlNutritionSanitation and vector controlEducation Improved standard of livingetc. (dont over-simplify!)

  • Demographic Transition

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

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

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

  • 1.4 Selected Historical Figures and EventsAn essential part of the outfit of the investigator in the field (Major Greenwood)Headings in this sectionBefore epi was a separate disciplineEmergence of epi in Victorian EnglandTwentieth century epiSmallpox (optional)

  • Before Epi was a Discipline pp. 11 12 We must understand the role of culture and western civilizationSelected points:Pre-scientific medicine was based on philosophy, religion, and moralityHippocrates symbolizes the shift to observation and the environmentThe Dark Ages represent a decline in enlightenment and public healthThe Protestant reformation brought with it important cultural changes

  • Western Civilization and Scientific Revolution (cont.)The renaissance brought with it an Age of Enlightenment Science liberates itself from philosophy, morality, and religionPost-modernism risks decadence

  • Demographic ApproachJohn Graunt (1620 1674)pp. 12 14

  • Graunts Life Table% surviving to age

    6641640262536164610566603761800

  • Lessons Learned from Graunt (Rothman, 1996)he was briefmade reasoning clearsubjected theories to multiple and varied testsinvited criticismwas willing to change ideas when confronted with contradictory evidenceavoided mechanical interpretations

  • Germ Theory(p. 14)HighlightsSelf-replicating (i.e., biological) agent Theory not accepted until late 1800sCompeting theory (miasma = atmospheric pollution) was accepted as late 1880sEarly contagionists Fracastoro (first cogent germ theory, 16th century)Jakob Henle & Robert Koch Pasteur Snow (see next section)Salmon (vector borne transmission)

  • John SnowQuintessential epidemiologic heroPhysiologist, anesthesiologist, & epidemiologistRemembered for Insightful theory of diseaseImpressive methods of studies

  • Snows Waterborne TheoryRefuted miasma in favor of contagion Theory on Clinical facts: symptoms and treatmentPhysiologic understanding: death due to fluid loss, smudging of blood, and asphyxiationEpidemiologic observations: epidemics followed routes of commerce, environmental contamination during epidemics

  • Components of Snows Contagion TheoryFree-living agentFecal-oral transmission (person-to-person)Agent multiplies within the hostWater-borne transmissionto age 16

  • Snows MethodsSnows methods are a model for non-experimental epiThree types of studiesEcological design: compared cholera rates by regionCohort design: compared cholera rates in exposed and non-exposed individualsCase-control design: compared exposure status in those with and without disease

  • Snows Ecological StudyFigure 1.13 (p. 24)

  • Ecological StudyKey data in Figure 1.13 (p. 24)Example of rate calculationRate St. Saviour = 45 / 19,709 100,000 = 227Rate Christchurch = 7 / 16,022 100,000 = 43Water sourceSt. Saviour Southwark and Vauxhall Water Only Christchurch multiple water companies including Vauxhall

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

  • Snows Case-Control StudyCollect data on all casesDetermine source of water for cases and non-cases See pp. 23 26 for examples of interviews

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

  • Exposure to Broad St. Pump WaterCase-control studies measure frequency of exposure (not frequency of disease)Consumption (exposure) frequent in cases61 cases exposure confirmed6 cases non-exposed6 cases equivocalExposure rare in non-casesExposure more frequent in cases than controls

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

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

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