Epidemiology Ch 4-1

8/11/2019 Epidemiology Ch 4-1

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Nies and

Nies and McEwen: Chapter 4:

ATI: Chapter 3

Epidemiology



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.



• 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.



• Objective 2: Define the following

epidemiological concepts, including theiridentifying factors and interconnection in

epidemiology and the disease process:

• 1. the epidemiological triangle• a. agent

• b. host

• c. environment



Objective 2



Agent Factors

• Nutritive elements

• Chemical agents

•

Physical agents• Infectious agents

Objective 2



Host Factors

• Genetics

• Age

• Sex

• Ethnic group• Physiological state

• Prior immunological experience

• Inter-current or preexisting disease

• Human behavior

Influence, exposure, susceptibility, or response to agent

Objective 2



Environmental Factors

•

Physical environment• Biological environment

• Socioeconomic environment

Influence Existence of the Agent, Exposure, or Susceptibility to Agent

Objective 2



The Epidemiological Triangle

Objective 2



• Objective 3. Define and differentiate, and beable to calculate, as well as discuss the

implication of the following epidemiologicalrates:

• 1. attack rate


• 3. prevalence rate• 4. age-adjusted rate


Incidence of

Rocky Mountain Spotted Fever

In The United States



“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

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.

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

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

Objective 3



Age-Adjusted Rate

• Age-adjustment or standardized rates reduce

bias due to unequivalent age distribution of

the populations being compared.

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.

Objective 3



Comparing Rates• The occupational health nurse notes that

during the past year 4 of 628 factoryemployees 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?

5 / 1000 = 0.005 4 / 628 = 0.0064

0.005 X 1000 = 5 per 1000 0.0064 X 1000 = 6.4 per 1000

Incidence in General Population Incidence in Factory

Objective 3



• Objective 4. Define and discuss the concepts

of risk and risk factors as the two terms relateto the epidemiological process



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).

Objective 4





Screening

• The purpose of screening programs is to identify risk factors and diseases

in their earliest stages. Screening is usually classified as a secondaryprevention 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)

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.

Objective 5



• Objective 6. Define, discuss, and differentiate

between the concepts of cross-sectional

studies and retrospective studies.



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.

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 thediseased group differs from the non-diseased

group in its exposure to a specific factor or

characteristic. Data collection extends back intime to determine previous exposure or risk

factors.

Objective 6



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


• 3. prevalence rate

• 4. age-adjusted 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.

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Epidemiology Ch 4-1