EPIDEMIOLOGY 1

• Epidemiology


  The study of the distribution and determinants of health-related states and events in specified populations, and the application of this study to the prevention and control of health problems
• Epidemiology


  • Epi (among, upon)
  • Demos (people, population)
  • Logos (study)
• Descriptive epidemiology


  • Distribution of health-related states
  • Identifying the pattern of disease as to person, time and place
• Analytic epidemiology


  • Determinants of health-related states
  • Understanding the causes or risk factors (also protective factors) that led to the disease
• Humorism/Humoralism (Hippocrates)


  If the four humors were balanced, then the body was in health
• Miasmic theory (Galen)


  "Bad air" causes the disease when someone breathes it in
• John Graunt


  • First to employ descriptive statistics in summarizing population data
  • Laid the groundwork for both demography and epidemiology
  • His work was used to estimate the London population and to create a warning system on the bubonic plague
  • 1620-1674
• John Snow


  • "shoe-leather epidemiology" - direct, door-to-door inquiry of the affected population
  • Linked cholera cases to water source allocation (natural experiment)
  • Refuted the miasmic theory for cholera (water-borne disease transmission)
  • 1813-1858
• William Farr


  • His classification system was the forerunner of the International Classification of Diseases (ICD)
  • Provided mortality data for Snow's study of cholera in London
  • Life Table Analysis
  • Related disease prevention to life expectancy
  • Captured occupational and residential differences in mortality
  • 1807-1883
• Peter Ludvig Panum


  • "Observations Made During the Epidemic of Measles on Faroe Islands in the Year 1846"
  • Incubation period
  • 1820-1885
• Ignaz Philipp Semmelweis


  • "Etiology, Concept and Prophylaxis of Childbed Fever (1847)"
  • Hygienic prevention
  • 1818-1865
• William Budd


  • "Typhoid Fever, its Nature, Mode of Spreading, and Prevention (1873)"
  • Isolation of infectious diseases
• Robert Koch


  • Put an end to the miasmic theory
• Disease causation


  The process by which diseases occur and progress in the human body
• Cause


  • Something that brings about an effect
  • an event, condition, characteristic or a combination of these factors which has a role in producing the health outcome
• Notes on the causal pie


  • Component causes can act far apart in time
  • Component cause can be the presence of a factor or the absence of a factor
  • A particular disease may result from a variety of different sufficient causes
  • Blocking any single component of any sufficient cause can already prevent disease development through that pathway
• Germ theory of disease


  Microorganisms known as pathogens or "germs" can cause disease
• Epidemiologic triad


  • Disease from the interaction of the 3 factors: agent, host (person) *susceptibility*, environment *conductive*
  • Limited with infectious diseases only
• Web of causation


  All causative factors are interconnected and there rarely is one causative factor for any disease or illness
• Causal pies


  • Aimed to explain the development of chronic diseases
• Component 


  • cause each slice of the pie is a factor contributing to the development of disease
• Sufficient


  • *completion of pie = disease development*
  • cause set of conditions that inevitably results to the outcome
• Necessary cause

  • component cause that is present in every sufficient cause