Epidemiology Professor Rush Community Nursing

The study of the distribution and determinants of health-related states or events in populations and the application of that study to control health problem

epidemiology

What are the purposes of epidemiology?

• Monitor population health trends

• Identify determinants of health and disease

• Investigate outbreaks

• Evaluate prevention strategies

• Guide public health nursing decisions

How do community/public health nurses use epidemiology?

To assess populations, identify risk groups, plan interventions, evaluate outcomes, and improve population health.

Linked disease to time, place, season, and environment.

Hippocrates

Identified diet as the cause of scurvy through observation and experimentation.

James Lind

Mapped cholera cases and removed the Broad Street pump handle to stop the outbreak.

John Snow

Used mortality statistics to improve sanitation during the Crimean War.

Florence Nightingale

Q: Which contributor would you identify in a question involving disease mapping?

A: John Snow.

Which contributor would you identify in a question involving mortality statistics and sanitation?

A: Florence Nightingale

What are the three parts of the epidemiologic triangle?

• Host

• Agent

• Environment

Susceptible human or animal that can develop disease.

host

Examples of host factors?

• Age

• Immunity

• Disease history

• Demographics

Factor that causes or contributes to disease.

agent

Examples of agents?

• Virus

• Bacteria

• Chemical

• Trauma

External factors that influence exposure and disease development.

environment

Examples of environmental factors?

• Pollution

• Climate

• Psychosocial environment

• Food storage conditions

Q: Potato salad left unrefrigerated at a picnic is what part of the epidemiologic triangle?

Environment

Relationship between a cause and an effect.

causality

A sequence of events leading to disease transmission; breaking any link can prevent disease.

chain of causation

Multiple interconnected factors contribute to disease rather than a single cause.

web of causality

Temporary protection from transferred antibodies.

passive immunity

• Maternal antibodies

• Immune globulin

• Snake antivenom

are all examples of

passive immunity

Protection produced by a person's own immune system after infection or vaccination.

active immunity

Immunity to one organism that provides protection against a related organism.

cross-immunity

Immunity from both prior infection and vaccination

hybrid immunity

Population-level protection that occurs when enough individuals are immune.

herd immunity

Probability that a disease or health condition will occur.

risk

What factors influence risk?

• Biology

• Environment

• Lifestyle

• Health care system

Formula for relative risk?

Incidence in exposed group ÷ incidence in unexposed group.

What does a relative risk > 1 mean?

Greater likelihood of disease in the exposed group.

Events that occur before disease develops, during its course, and through its outcome.

natural history of disease

What concept is closely linked to the natural history of disease?

levels of prevention

Number of NEW cases occurring during a specified time period.

incidence

ALL existing cases in a population at a specific time.

prevalence

Frequency of illness in a population.

morbidity

Frequency of death in a population.

mortality

Which measure shows burden of disease?

morbidity

Which measure shows public health impact and severity?

mortality

What are vital statistics?

Births, deaths, marriages, divorces.

What information comes from census data?

Age, race, sex, income, occupation.

Why are reportable diseases important?

Support rapid public health action.

Examples of registries and surveillance systems?

• Cancer registries

• BRFSS

• YRBSS

Purpose of environmental monitoring?

Assess environmental hazards and exposure risk.

What does descriptive epidemiology study?

Person, Place, and Time.

Goal of descriptive epidemiology?

identify the cause of health problems and develop measures to prevent illness.​

Observe and describe patterns of health-related conditions that occur naturally​

• Data on Measles Immunizations​

• Cases of STDs in past month​

• Automobile crashes near high school​

• Suggest hypothesis for further testing​

descriptive epidemiology

• # of deaths due to specific disease​

• Time delay to gather data

counts - descriptive epidemiology

• Proportion of people with given health problem​

• Total number of people is denominator​

rates - descriptive epidemiology

formula for incidence

number of persons developing a disease / total number at risk per unit of time

• Refers to all new cases of a disease or health condition appearing during a given time​

incidence

All people with a particular health condition in a given population at a given point in time

describes patterns of occurrence

prevalence

the prevalence rate over a defined period of time​

period prevalence rate

formula for period prevalence rate

number of persons with a characteristic during a period of time / total number in population

formula for prevalence rate

number of persons with a characteristic / total number in population

Goal of descriptive epidemiology?

Describe patterns and generate hypotheses.

Starts with people who have a disease and compares with those who lack it

looks backward for exposures. (Retrospective)

A community nurse identifies:

• 100 adults with lung cancer (cases)

• 100 adults without lung cancer (controls)

The nurse reviews their smoking histories from the past 20 years.

case-control study

Starts with exposure and follows people over time to see who develops disease. group of people who share a common experience in a specific time period

ex. elderly, employees of specific industry, environmental hazard exposures

community health nurse follows:

• 500 factory workers exposed to asbestos

• 500 factory workers not exposed

The groups are followed for 20 years to see who develops lung disease.

people are the focus of the study

cohort study

Examines variables at one point in time. (broken window index)

A school nurse surveys 500 high school students during October and records:

• Current vaping status

• Current anxiety levels

cross-sectional study

Looks backward using existing data to find casual relationship

A nurse reviews medical records from 2015-2025 to determine whether childhood obesity was associated with Type 2 Diabetes later in life.

retrospective study

looks forward in time to find casual relationship

cancer prevention study

A public health nurse enrolls 1,000 children today and follows them for 10 years to determine whether physical activity lowers obesity rates.

prospective study

Investigator manipulates a variable and observes outcomes.

used to confirm observational studies

A county health department introduces a new smoking cessation program in one community while another community receives standard education.

experimental study

Which study is considered retrospective and begins with cases?

case-control study

Which study follows exposed groups over time?

cohort study

How does epidemiology support the 10 Essential Public Health Services?

Assessment, policy development, and assurance

What three levels do community/public health nurses use epidemiologic data?

Individual, family, and population levels.

Who is associated with scurvy?

james lind

Who is associated with cholera mapping?

john snow

Who linked disease to environment?

hippocrates

Who used mortality statistics to improve sanitation?

florence nightingale

What are three intervention points in the epidemiologic triangle?

host, agent, environment

What is the purpose of Bradford Hill criteria?

To evaluate whether an exposure is likely related to an outcome.

Health is influenced by biologic, behavioral, social, environmental, policy, cultural, and economic factors

ecologic model

Multiple interacting factors contribute to disease.

web of causality

Prevalence measured over a defined time period

period prevalence

Why are rates useful?

They allow comparison between populations of different sizes.

Controls for differences in age distribution when comparing populations.

age adjustment

What are the three components of descriptive epidemiology?

person, place, time

What is the first step of epidemiologic research?

identify the problem

What are the steps of epidemiologic research?

Identify problem → Literature review → Study design → Data collection → Analysis → Conclusions → Dissemination.

Disease occurrence exceeds expected frequency

epidemic

Epidemic spreads worldwide

pandemic

Constantly present in a population

endemic

Study of distribution and determinants of health in populations

epidemiology