Transcript Nies and McEwen: Chapter 4: Epidemiology ATI: Chapter 3

Epidemiology
Nies and
Nies and McEwen: Chapter 4:
ATI: Chapter 3
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.
2.
3.
4.
5.
attack rate
incidence rate
prevalence rate
age-adjusted rate
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 their
identifying factors and interconnection in
epidemiology and the disease process:
•
1. the epidemiological triangle
•
a. agent
•
b. host
•
c. environment
Objective 2
Objective 2
Agent Factors
•
•
•
•
Nutritive elements
Chemical agents
Physical agents
Infectious agents
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
Objective 2
Environmental Factors
Influence Existence of the Agent, Exposure, or Susceptibility to Agent
• Physical environment
• Biological environment
• Socioeconomic environment
Objective 2
The Epidemiological Triangle
• 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.
3.
4.
5.
incidence rate
prevalence rate
age-adjusted rate
proportionate mortality rate
Incidence of
Rocky Mountain Spotted Fever
In The United States
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
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
X 1000
– 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
= 3750 =0.02 x 1000 = 20 per 1000 per time period
4000 – 250
Objective 3
Prevalence Rate
• Prevalence rates
– All cases
– Number of Existing Cases X 1000
–
Total Population
– Example: In a population of 4000 , 250 individuals have a particular
disease.
– 250
= 0.0625 X 1000 = 62.5 per 1000
– 4000
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 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
5 / 1000 = 0.005
0.005 X 1000 = 5 per 1000
Incidence in Factory
4 / 628 = 0.0064
0.0064 X 1000 = 6.4 per 1000
• Objective 4. Define and discuss the concepts
of risk and risk factors as the two terms relate
to the epidemiological process
Objective 4
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 5. Define, discuss, and differentiate
the concepts of screening and surveillance as
they relate to the epidemiological process
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)
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 6. Define, discuss, and differentiate
between the concepts of cross-sectional
studies and retrospective studies.
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.
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.
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.