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90110 pp tx_ch03
 

90110 pp tx_ch03

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    90110 pp tx_ch03 90110 pp tx_ch03 Presentation Transcript

    • Epidemiology: The Study of Disease, Injury, and Death in the Community Chapter 3
    • Introduction
      • Epidemiology = population medicine
      • Epidemiologists concerned with course of disease in a population
      • Collect information about disease status of a community
        • How many people are sick? Who is sick? When did they become sick? Where do they live?
      • Data can be used to prevent disease outbreaks or determine effectiveness of prevention effort
    •  
    • Definitions
      • Epidemiology: study of distribution and determinants of health-related states or events in specified populations
      • Epidemic: unexpectedly large number of cases of an illness, specific health-related behavior or event, in a particular population
      • Endemic: disease that occurs regularly in a population as a matter of course
      • Pandemic: outbreak over wide geographic area
    • The Epidemics?
    •  
    • The Importance of Rates
      • Rates allow for comparison of outbreaks at different times or in different places
      • Cases: people afflicted (those who are sick)
      • Rates: number of events in a given population over a given period of time or given point in time
        • Natality (birth), morbidity (sickness), mortality or fatality (death) rates
      • Population at Risk: those susceptible to particular disease or condition
    • Morbidity Rates
      • Incidence rate: number of new health-related events or cases of a disease in a population exposed to that risk during a particular period of time, divided by total # in same population
      • Prevalence rate: number of new and old cases in a given period of time, divided by total # in that population
      • Attack rate: incidence rate calculated for a particular population for a single disease outbreak; expressed as a percentage
    •  
      • Incidence rates important to study of acute diseases
        • Acute disease: lasts three months or less
      • Prevalence rates useful for study of chronic diseases
        • Chronic disease: last longer than three months
      • Incidence and prevalence rates expressed as crude or specific
      Incidence, Prevalence, and Attack Rates
    • Incidence, Prevalence, and Attack Rates
    • Crude and Age-Adjusted Rates
      • Crude rates: denominator includes the total population
        • Crude birth rate: # of live births in given year, divided by midyear population
        • Crude death rate: # of deaths in given year from all causes, divided by midyear population
      • Age-adjusted rates: used to make comparisons of relative risks across groups and over time when groups differ in age structure
    •  
    • Crude and Age-Adjusted Rates
    • Specific Rates
      • Measure morbidity and mortality for particular populations or diseases
      • Case fatality rate: percentage of cases of a particular disease that result in death
      • Proportionate mortality ratio: percentage of overall mortality in a population that is attributable to a particular cause
    • Important Rates in Epidemiology
    • Reporting of Birth, Deaths, and Diseases
      • Physicians, clinics, and hospitals required to report births, deaths, and notifiable diseases
        • Notifiable diseases: infectious diseases in which health officials request or require reporting
          • Can become epidemics
          • Health officials maintain weekly records
      • Various challenges to maintaining accurate data
    • Notifiable Disease Scheme
    • Standardized Measurements of Health Status of Populations
      • Mortality statistics most reliable measure of population health status
        • Easier to track death than illness
      • Life expectancy: average number of years a person from a specific cohort is projected to live from a given point in time
      • Years of potential life lost (YPLL): number of years lost when death occurs before one’s life expectancy
    • Life Expectancy Figures
    • Years of Potential Life Lost
      • Subtract person’s age at death from his or her life expectancy
      • Difficult to determine because life expectancy changes at different ages
      • Weighs death of young person as counting more than death of old
    •  
    • Sources of Standardized Data
      • Various valid sources have specific value and usefulness to those in public health
        • U.S. Census
          • Taken every 10 years
          • Enumeration of the population
          • More complex now
            • Gathers data on race, age, income, employment, education, and other social indicators
        • Statistical Abstract of the United States
          • Book published annually by Bureau of Census
          • Summary of statistics on social, political, and economic organization of the United States
        • Monthly Vital Statistics Report
          • Vital statistics are summaries of records of major life events: birth, death, marriage, divorce
          • Published by National Center for Health Statistics under the CDC
          • Also calculates death rates by race and age
      Sources of Standardized Data (ctd)
        • Morbidity and Mortality Weekly Report (MMWR)
          • Prepared by CDC from state health department reports
          • Reports morbidity and mortality data by state and region of U.S.
          • Reports outbreaks of disease, environmental hazards, unusual cases, or other public health problems
      Sources of Standardized Data (ctd)
    •  
    •  
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    • National Health Surveys
      • National Health Survey Act of 1956 authorized continuing survey of amount, distribution, and effects of illness and disability in the U.S.
      • Three types of surveys
        • Health interviews of people
        • Clinical tests, measurements, and physical examinations
        • Surveys of places where people receive medical care
    • Some National Health Surveys
      • National Health Interview Survey (NHIS)
        • Conducted by NCHS
        • Questions respondents about their health
      • National Health and Nutrition Examination Survey (NHANES)
        • Assesses health and nutrition status through mobile examination center
      • Behavioral Risk Factor Surveillance System (BRFSS); National Health Care Survey (NHCS)
    • Epidemiological Studies
      • Investigations carried out when disease or death occurs in unexpected or unacceptable numbers
      • Descriptive studies
        • Describe epidemics with respect to person, place, and time
      • Analytic studies
        • Aimed at testing hypotheses
    • Descriptive Studies
      • Who?
        • Case count, followed by who is ill (children, men, women, race, etc.)
      • When?
        • Time of onset for each case
        • Epidemic curves created
      • Where?
        • Determine residential address and travel history
    • Epidemic Curves
      • Graphic display of the cases of disease according to the time or date of onset of symptoms
      • Secular, seasonal, and single epidemic curves
      • Single epidemic curves
        • Point source epidemic curve
        • Propagated epidemic curve
    • Secular Epidemic Curve
    • Seasonal Epidemic Curve
    • Point Source Epidemic Curve
    • Propagated Epidemic Curve
    • Analytic Studies
      • Test hypotheses about relationships between health problems and possible risk factors
        • Observational studies: investigator observes natural course of events, noting exposed vs. unexposed and disease development
          • Case/control studies
          • Cohort studies
        • Experimental studies: investigator allocates exposure and follows development of disease
    • Case/Control Studies
      • Case/Control
        • Compares those with disease to those without but with similar background and/or with prior exposure to certain risk factors
          • Aimed at identifying factors more common in case than control group
    • Cohort Studies
      • Cohort is classified by exposure to one or more risk factors and observed to determine rate of disease development
        • Cohort: group of people who share important demographic characteristic
      • Odds ratio
      • Relative risk
    • Experimental Studies
      • Carried out to identify cause of disease or determine effectiveness of vaccine, drug, or procedure
        • Control for variables
          • Control groups
          • Randomization
          • Blinding
        • Placebo: blank treatment
    • Criteria of Causation
      • Questions exposure causing development of disease
      • Criteria
        • Strength
        • Consistency
        • Specificity
        • Temporality
        • Biological plausibility
    •  
    • Discussion Questions
      • How can data collection for notifiable diseases be improved?
      • Why is tracking vital statistics so important?
      • How does calculating Years of Potential Life Lost change the way we think about community health efforts?