6 epid

• Observational studies


  The epidemiologist simply observes the exposure and disease status of each study participant and is often the first step in an epidemiological investigation
• Types of Observational studies

  • Descriptive Epidemiology
  • Analytic Epidemiology
• Descriptive Epidemiology


  Covers the 5W's: What, Who, Where, When, Why/how
• The 5W's of descriptive epidemiology

  • What = health problem of concern
  • Who = person
  • Where = place
  • When = time
  • Why/how = causes, risk factors, modes of transmission
• Epidemiologists strive for similar comprehensiveness in characterizing an epidemiologic event
• Synonyms for the 5 W's

  • Case definition
  • Person
  • Place
  • Time
  • Causes/risk factors/modes of transmission
• Descriptive epidemiology


  • Covers time, place, and person
• Time


  The occurrence of disease changes over time, some regularly, others unpredictably
• Diseases with seasonal patterns

  • Influenza (winter)
  • West Nile virus infection (August-September)
• Diseases without seasonal patterns

  • Hepatitis B
  • Salmonellosis
• Place


  Describing the occurrence of disease by place provides insight into the geographic extent of the problem and its geographic variation
• Person


  Personal characteristics may affect illness, so data is organized and analyzed by attributes like age, sex, ethnicity, socioeconomic status
• Age


  The single most important "person" attribute, as almost every health-related event varies with age
• Sex


  Males have higher rates of illness and death than females for many diseases, due to genetic, hormonal, anatomic, or other inherent differences
• Ethnic and racial groups

  Differences in racial, ethnic, or other group variables may reflect differences in susceptibility, exposure, or other factors that influence disease risk
• Socioeconomic status


  Difficult to quantify, made up of variables like job, family income, educational achievement, and living conditions
• Cross-sectional study


  A sample of persons from a population is enrolled and their exposures and health outcomes are measured at the same time, assessing the prevalence of the health outcome at that point in time
• Analytic Epidemiology


  Concerned with the search for causes and effects, using quantitative methods to identify associations between exposures and outcomes and test hypotheses about causal relationships
• Types of Analytical studies

  • Cohort study
  • Case-control study
  • Experimental studies
• Cohort study


  The epidemiologist records whether each study participant is exposed or not, and then tracks the participants to see if they develop the disease of interest
• Case-control study


  Investigators enroll a group of people with disease (cases) and a group without disease (controls), then compare previous exposures between the two groups

  
• Experimental studies


  The investigator determines the exposure for each individual or community through a controlled process, and then tracks them over time to detect the effects of the exposure
• Clinical trials


  Research studies performed in people that are aimed at evaluating a medical, surgical, or behavioral intervention
• Community trials


  The treatment groups are communities rather than individuals, appropriate for diseases influenced by social conditions and prevention efforts targeting group behavior
• Observational studies


  The epidemiologist simply observes the exposure and disease status of each study participant and is often the first step in an epidemiological investigation
• Types of Observational studies

  • Descriptive Epidemiology
  • Analytic Epidemiology
• Descriptive Epidemiology


  Covers the 5W's: What, Who, Where, When, Why/how
• The 5W's of descriptive epidemiology

  • What = health problem of concern
  • Who = person
  • Where = place
  • When = time
  • Why/how = causes, risk factors, modes of transmission

  
• Epidemiologists strive for similar comprehensiveness in characterizing an epidemiologic event, whether it be a pandemic of influenza or a local increase in all-terrain vehicle crashes
• Descriptive epidemiology covers time, place, and person
• Time


  The occurrence of disease changes over time. Some changes occur regularly, while others are unpredictable
• Diseases with seasonal patterns

  • Influenza (winter)
  • West Nile virus infection (August– September)
• Diseases without seasonal patterns

  • Hepatitis B
  • Salmonellosis
• Place


  Describing the occurrence of disease by place provides insight into the geographic extent of the problem and its geographic variation

  
• Person


  Personal characteristics may affect illness, so data is organized and analyzed by attributes like age, sex, biologic characteristics, acquired characteristics, activities, or living conditions
• Age


  The single most important "person" attribute, because almost every health-related event varies with age
• Sex


  Males have higher rates of illness and death than females for many diseases, due to genetic, hormonal, anatomic, or other inherent differences
• Ethnic and racial groups


  Analyzing data by biologic, cultural or social grouping may reflect differences in susceptibility, exposure, or other risk factors
• Socioeconomic status


  Difficult to quantify, made up of variables like job, family income, education, and living conditions
• Cross-sectional study


  A sample of persons is enrolled and their exposures and health outcomes are measured at the same time, assessing the prevalence of the health outcome at that point in time