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  1. Epidemiology Nies and Nies and McEwen: Chapter 4: ATI: Chapter 3

  2. Objectives --Epidemiology • Objective 1. Define and discuss the following terms; compare and contrast the following methods and concepts of epidemiology related to community health 1. descriptive epidemiology 2. analytic epidemiology • Objective 2. Define the following epidemiological concepts, including their identifying factors and interconnection in epidemiology and the disease process: • 1. epidemiological triangle • a. agent • b. host • c. environment • Objective 3. Define and differentiate, and be able to calculate, as well as discuss the implication of the following epidemiological rates: • 1. attack rate • 2. incidence rate • 3. prevalence rate • 4. age-adjusted rate • 5. proportionate mortality rate • Objective 4. Define and discuss the concepts of risk and risk factors as the two terms relate to the epidemiological process • Objective 5. Define, discuss, and differentiate the concepts of screening and surveillance as they relate to the epidemiological process • Objective 6. Define, discuss, and differentiate between the concepts of cross-sectional studies and retrospective studies.

  3. Objective 1. Define and discuss the following terms; compare and contrast the following methods and concepts of epidemiology related to community health • descriptive epidemiology uses person, place, and time variables to describe disease patterns. • analytic epidemiology analyzes complex relationships among determinants of diseases. The focus is on disease etiology.

  4. Objective 2: Define the following epidemiological concepts, including their identifying factors and interconnection in epidemiology and the disease process: • 1. the epidemiological triangle • a. agent • b. host • c. environment

  5. Objective 2

  6. Objective 2 Agent Factors • Nutritive elements • Chemical agents • Physical agents • Infectious agents

  7. Objective 2 Host Factors Influence, exposure, susceptibility, or response to agent • Genetics • Age • Sex • Ethnic group • Physiological state • Prior immunological experience • Inter-current or preexisting disease • Human behavior

  8. Objective 2 Environmental Factors • Physical environment • Biological environment • Socioeconomic environment Influence Existence of the Agent, Exposure, or Susceptibility to Agent

  9. Objective 2 The Epidemiological Triangle

  10. Objective 3. Define and differentiate, and be able to calculate, as well as discuss the implication of the following epidemiological rates: • 1. attack rate • 2. incidence rate • 3. prevalence rate • 4. age-adjusted rate • 5. proportionate mortality rate Incidence of Rocky Mountain Spotted Fever In The United States

  11. Objective 3 “Epidemiological Rates” • Rates are arithmetic expressions that help practitioners consider a count of an event relative to the size of the population from which it is extracted Rate: Numerator/Denominator = Number of health events in a specified period/Population in same area in same specified period × k

  12. Objective 3 Attack Rate • An attack rate is a special incidence rate that documents the number of new cases of a disease in those exposed to a disease.

  13. Objective 3 Incidence Rate • Incidence rates • New cases • Number of New Cases in a Given Time Period • Population at Risk During Same Time Period • Example: In a total population of 4000, where 250 individuals already have the disease, 75 new cases are reported. • 75 75 4000 – 250 3750 X 1000 = = 0.02 x 1000 = 20 per 1000 per time period

  14. Objective 3 Prevalence Rate • Prevalence rates • All cases • Number of Existing Cases • Total Population • Example: In a population of 4000 , 250 individuals have a particular disease. • 250 • 4000 X 1000 = 0.0625 X 1000 = 62.5 per 1000

  15. Objective 3 Age-Adjusted Rate • Age-adjustment or standardized ratesreduce bias due to unequivalent age distribution of the populations being compared.

  16. Objective 3 Proportionate Mortality rate • The proportionate mortality rate (PMR) represents the percentage of deaths resulting from a specific cause relative to deaths from all causes.

  17. Objective 3 Comparing Rates • The occupational health nurse notes that during the past year 4 of 628 factory employees have developed asbestososis. He checks with MMWR, and notes that the incidence rate of asbestososis in the general population is 5 per 1000. • Is the rate for the factory higher or lower than for the general population? Incidence in General Population Incidence in Factory 5 / 1000 = 0.005 4 / 628 = 0.0064 0.005 X 1000 = 5 per 1000 0.0064 X 1000 = 6.4 per 1000

  18. Objective 4. Define and discuss the concepts of risk and risk factors as the two terms relate to the epidemiological process

  19. Objective 4

  20. Objective 4 RISK FACTORS • a. Identification of risk factors is closely associated with chronic disease reduction. • b. Risk factors are variables that have been shown to increase the rate of disease in persons who have them or have been exposed to them. • c. Identification of risk factors is critical to development of prevention interventions. • d. Risk is the likelihood that healthy persons exposed to a factor will acquire a specific disease. •  e. Risk factor refers to the specific exposure factor. Risk factors may be fixed characteristics –non-modifiable-- (i.e., age, sex, genetics), or modifiable--lifestyle factors (dietary habits, exercise regimens), or external to the individual (i.e., cigarette smoking, stress, noise).

  21. Objective 5. Define, discuss, and differentiate the concepts of screening and surveillance as they relate to the epidemiological process

  22. Objective 5 Screening • The purpose of screening programs is to identify risk factors and diseases in their earliest stages. Screening is usually classified as a secondary prevention activity because disease is discovered after a pathological change has occurred. • Guidelines for screening programs include: • 1. Adequate and appropriate follow-up should be planned for those who test positive. • 2. Early diagnosis of the disease should be beneficial. • 3. Acceptable and medically sound treatment should be available. • 4. Procedures for ensuring confidentiality should be in place. • 5. Tests must be cost effective and acceptable to the client. • 6. Costs of program, follow-up, and resulting medical care should have a bearing on the decision to screen. • 7. Screening tests should ideally have high sensitivity (the ability of a test to detect those with the disease) and specificity (the extent to which a test can identify those without the disease)

  23. Objective 5 Surveillance • Surveillance allows ongoing collection of information by monitoring changes in disease frequency and trends in occurrence of risk factors. • The nurse evaluates trends in morbidity by identifying new cases and calculating incidence rates.

  24. Objective 6. Define, discuss, and differentiate between the concepts of cross-sectional studies and retrospective studies.

  25. Objective 6 Cross-Sectional Studies • Cross-sectional studies (also known as prevalence or correlational studies) examine relationships between potential causal factors and disease at a point in time.

  26. Objective 6 Retrospective Studies • Retrospective (case control) studies compare a group of individuals known to have a disease with a similar group of individuals who do not have the disease to determine whether the diseased group differs from the non-diseased group in its exposure to a specific factor or characteristic. Data collection extends back in time to determine previous exposure or risk factors.

  27. Objectives ~ Epidemiology • Objective 1. Define and discuss the following terms; compare and contrast the following methods and concepts of epidemiology related to community health 1. descriptive epidemiology 2. analytic epidemiology • Objective 2. Define the following epidemiological concepts, including their identifying factors and interconnection in epidemiology and the disease process: • 1. epidemiological triangle • a. agent • b. host • c. environment • Objective 3. Define and differentiate, and be able to calculate, as well as discuss the implication of the following epidemiological rates: • 1. attack rate • 2. incidence rate • 3. prevalence rate • 4. age-adjusted rate • 5. proportionate mortality rate • Objective 4. Define and discuss the concepts of risk and risk factors as the two terms relate to the epidemiological process • Objective 5. Define, discuss, and differentiate the concepts of screening and surveillance as they relate to the epidemiological process • Objective 6. Define, discuss, and differentiate between the concepts of cross-sectional studies and retrospective studies.