principles of epidemiology

Overview

This discussion board is aligned with the module objective “Demonstrate community assessments and apply the principles of epidemiology.” As part of the discussion you will:

· Review the concepts of epidemiology in disease control and prevention (p. 70-78).

· Apply ecosocial epidemiology paradigm (macro-level) to one of your chosen diagnosis from module 1 written assignment (p.72).

Your initial post must be posted before you can view and respond to colleagues, must contain minimum of two (2) references, in addition to examples from your personal experiences to augment the topic. The goal is to make your post interesting and engaging so others will want to read/respond to it. Synthesize and summarize from your resources in order to avoid the use of direct quotes, which can often be dry and boring. No direct quotes are allowed in the discussion board posts.

Post a thoughtful response to at least two (2) other colleagues’ initial postings. Responses to colleagues should be supportive and helpful (examples of an acceptable comment are: “This is interesting – in my practice, we treated or resolved (diagnosis or issue) with (x, y, z meds, theory, management principle) and according to the literature…” and add supportive reference. Avoid comments such as “I agree” or “good comment.”

Points: 30

Due Dates:

· Initial Post: Fri, Sep 3 by 11:59 p.m. Eastern Standard Time (EST) of the US.

· Response Post: Sun, Sep 5 by 11:59 p.m. Eastern Standard Time (EST) of the US – (the response posts cannot be done on the same day as the initial post).

References:

· Initial Post: Minimum of two (2) total references: one (1) from required course materials and one (1) from peer-reviewed references.

· Response posts: Minimum of one (1) total reference: one (1) from peer-reviewed or course materials reference per response.

Words Limits

· Initial Post: Minimum 200 words excluding references (approximately one (1) page)

· Response posts: Minimum 100 words excluding references.

Chapter 5

Epidemiology

Epidemiology Is …

… the study of the distribution

and determinants of health and

disease in human populations

(Harkness, 1995)

… the principal science of

public health

Historical Perspective

 Investigations of disease pattern in the community; comparing people who had disease or who remained healthy

 Person-Place-Time Model  Person: “Who” factors, such as demographic

characteristics, health, and disease status

 Place: “Where” factors, such as geographic location, climate and environmental conditions, political and social environment

 Time: “When” factors, such as times of day, week, or month and secular trends over months and year

Different Types of Epidemiology

 Descriptive Epidemiology  Study of the amount and distribution of disease

 Used by public health professionals

 Identified patterns frequently indicate possible causes of disease

 Analytic Epidemiology  Examine complex relationships among the many

determinants of disease

 Investigation of the causes of disease, or etiology

Epidemiological Triangle

Figure 5-1

Agent of Disease (Etiologic Factors)

 Nutritive elements

 Excesses, deficiencies

 Chemical agents

 Poisons, allergens

 Physical agents

 Ionizing radiation, mechanical

 Infectious agents

 Metazoa, protozoa, bacteria, fungi, rickettsia,

viruses

Host Factors–Intrinsic Factors (Susceptibility, or Response to Agent)

 Genetic

 Age

 Sex

 Ethnic group

 Physiological state

 Prior immunological experience

 Active/, passive

 Intercurrent or preexisting disease

 Human behavior

Environmental Factors— Extrinsic

Factors…

… influence existence of the agent, exposure,

or susceptibility to agent

 Physical environment

 Biological environment

 Human populations, flora, fauna

 Socioeconomic environment

 Occupation, urbanization and economic

development, disruption

Wheel Model of

Human-Environment Interaction

Figure 5-2

Redrawn from Mausner JS,

Kramer S: Mausner and

Bahn epidemiology: an

introductory text, ed 2,

Philadelphia, 1985,

Saunders.

Web of Causation

Figure 5-3

From Friedman GD:

Primer of epidemiology, ed

4, New York, 1994,

McGraw-Hill.

Ecosocial Approach

 Emphasize the role of evolving macro-level

socioenvironmental factors along with

microbiological process in understanding

health and illness (Smith & Lincoln, 2011)

 Challenges the more individually focused risk

factor approach to understanding disease

origins

Calculation of 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

 Number of health events in a specified period

 Population in same area in same specified period

• Proportion multiplied by a constant (k)

• For example, the rate can be the number of cases of a disease occurring for every 1000, 10,000 or 100,000

people in the population

 Can make meaningful comparisons

Morbidity Rates

 Incidence rates

 New cases or conditions

 Attack rate

• Number of new cases of those

exposed to the disease

 Prevalence rates

 All cases of a specific

disease or condition at

a given time

Prevalence Pot The relationship between incidence

and prevalence

Figure 5-4

Redrawn from Morton RF, Hebel JR,

McCarter RJ: A study guide to epidemiology

and biostatistics, ed 3, Gaithersburg, MD,

1990, Aspen Publishers.

Morbidity Rates (Cont.) Incidence Rate

Prevalence Rate

Number of existing cases

Total Population

_____

Number of new cases

_in given time period

Population at risk in

same time period

___75___

4000–250

× 1000

= 0.02

0.02 × 1,000 = 20 per 1000 per time period

250

4000 = 0.0625

0.0625 × 1000 = 62.5 per 1000

Mortality Rates (routinely collected birth and death rates)

 Other rates

 Crude rates

 Age-specific rates

 Age-adjusted rates or

standardization of rates

 Proportionate mortality

ratio (PMR)

Number of deaths in year

Total population size

_1720_

200,000

× 100,000

= 0.0086

Number of births in year

Total population size

_2900_

200,000

× 100,000

= 0.0145

Concept of Risk

 Risk—probability of an adverse event

 Risk factor

 Refers to the specific exposure factor

 Often external to the individual

 Attributable risk

 Estimate of the disease burden in a population

 Relative risk ratio

 Divide the incidence rate of disease in the

exposed population by the incidence rate of

disease in the nonexposed population.

Use of Epidemiology

 Disease prevention

 Primary prevention

• Health promotion and specific prevention

 Secondary and tertiary prevention

 Establishing causality

 Screening

 Surveillance

Use of Epidemiology (Cont.)

 Health services

 Used to describe the distribution of disease

and its determinants in populations

 Study population health care delivery

 Evaluate use of community health services

 Nurses must apply findings in practice

 Incorporate results into prevention

programs for communities and at-risk

populations

 Extend application into major health policy

decisions

Community health nurses should exercise

“social responsibility” in applying

epidemiological findings, but this will require the

active involvement of the consumer.

Community health nurses collaborating with

community members can combine

epidemiological knowledge and aggregate-level

strategies to affect change on the broadest

scale.

Epidemiological Methods

 Descriptive epidemiology

 Focuses on the amount and distribution of health

and health problems within a population

 Analytic epidemiology

 Investigates the causes of disease by determining

why a disease rate is lower in one population

group than in another

Analytic Epidemiology

 Observational studies

 Descriptive purposes

 Etiology of disease

 No manipulation by investigator

 Cross-sectional studies

 Sometimes called prevalence or correlational

studies

 Examine relationships between potential causal

factors and disease at a specific time

 Impossible to make causal inferences

Analytic Epidemiology (Cont.)

 Retrospective studies

 Compare individuals with a particular condition or

disease with those who do not have the disease

 Data collection extends back in time

 Prospective studies

 Monitor a group of disease-free individuals to

determine if and when disease occurs

 Cohort shares a common experience within a

defined time period

 Monitors cohort for disease development

Analytic Epidemiology (Cont.)

 Experimental design

 Also called a Randomized Clinical Trial (RCT)

• Subjects assigned to experimental or control group

• Apply experimental methods to test treatment and prevention strategies

• Ethical considerations with human subject rights review

 Also useful for investigating chronic disease

prevention

principles of epidemiology