Chapter 2

Prospective

________- collect data as the group is followed forward in time.

ENVIRONMENT

________- allows the agent to move to the host. Ex. Air, water, soil, and fomite (inanimate object)

Temporality

________- Cause always occurs before effect.

Snow

________- determined cholera was more likely obtained from water downstream. He removed the water pump handle to stop the outbreak.

Biological Gradient

________- A dose- response relationship exists, greater dose= greater response.

Strength

________ strong associations support casual Relationships. Ex. Heavy smokers are 30 times more likely to die from lung CA than non-smokers.

Cohort study

An identified group/population at risk is followed over a period of time to determine the exposure that causes disease.

Environmental epidemiology

________- The study of diseases and health conditions occurring in the population that are linked to environmental factors.

Incidence

________- occurrence of new diseases or mortality in a defined period of observation in a specific population.

An example of an ecological study of perchlorate.

________ studied with drinking water exposed to perchlorate vrs drinking water without exposure= No greater outcome of ADHA /Autism.

Prevalence

________- total number of existing cases of a disease, health condition or deaths in a population at some designated time.

Point prevalence formula

________- # of people ill divided by the total number in the group. Answer divided by 100 to get the %.

Point Prevalence

Prevalence measured at a particular point in time.

Hippocrates

Stated water quality and air quality had a role in causing disease.

Percival Pott

Observed that chimney sweeps had a high incidence of scrotal cancer and advised to be the weekly.

How epidemiology aids environmental health.

Studies concerns with population, uses observational data, uses methodology for study designs, and uses descriptive and analytic studies.

What is the purpose of an epidemiological study?

Using observational science which naturally occurs in situations to study the occurrence of disease

How is prevalence measure used?

All numbers of existing cases of a disease, health condition, or death in a population at some designated time.

Incidence formula

A period of time X A multiplier (ex. 100,000) DIVIDED BY The total population at risk

Population at risk definition

Members of the population who are capable of developing the disease or condition being studied.

Case fatality rate

A measure of lethality of a disease.

Case fatality rate formula

# of deaths due to the disease DIVIDED BY The number of cases of the disease X The period of time X 100 =

What is a cross-sectional study

Examines the relationship between disease or other health related characteristics and other variables of interest as they exist in a defined population at one particular time.

How is data gathered for a cross-sectional study?

A questionnaire is used to collect data.

Why does a cross-sectional study not prove a casual relationship?

Because it identifies exposure and effect at the same time. But it justifies further studies to be done.

Case control study

Study in which subjects who participate are defined on the basis of (presence) cases or absence (controls) of outcomes of interest.

What does the odds ratio measure?

A measure of association for case control studies.

Interpretation Odds ratio if > 1.0

Exposure is more likely associated with cases then controls, so exposure is most likely associated with disease.

Interpretation Odds ratio < 1.0

Disease is not likely associated with the exposure.

Retrospective

If data has been collected on the group in the past.

What is the best measure of association for a cohort study?

Risk ratio or relative risk.

How is SMR are used?

It’s used to observe deaths in the study group to expect and deaths in the general population.

Standardized mortality ratio formula

Deaths observed DIVIDED BY deaths expected X 100 =

What is perchlorate?

A chemical salt.

What are the hazards associated with perchlorate?

It is found in the production of rocket propellant, fireworks, matches, and explosives.

What is the epidemiologic triangle model of causality?

Used for describing the causality of infection diseases with the host environment an agent.

AGENT

Could be biological, ex bacteria, protozoan,fungi, or virus. Chemical ex. Toxic, radiation, or radioactive particle.

HOST

Must be susceptible to the agent.

7 criteria of causality.

Strength, consistency, specificity, temporality, biological gradient, biological possibility, and coherence.

Consistency

Association is observed repeatedly. An example is a study of smokers versus cancer has been found repeatedly.

Specificity

Specific Association is one that has a specific exposure that causes a specific disease.

Biological plausibility

Agrees with the current understanding of pathological processes.

Coherence

Compatible and does not seriously conflict with current scientific knowledge.

Ecological study

The incidence Of a disease and one geographical area is compared to that of another area. An example is cancer mortality in areas with hazardous waste sites versus areas without hazardous waste sites.

Risk ratio interpretation > 1.0

If risk ratio is greater than 1.0, then the risk of disease is greater in the exposed group than the non-expose group. The greater the risk ratio the greater the risk the disease is associated with exposure.

Risk ratio interpretation if 1.0

The risk is the same for exposed and unexposed.

Risk ratio interpretation if < 1.0

The exposure is protective of health.

Risk ratio formula

How do you Cohart studies in case control study is different in regard to knowing the population at risk?

A cohort study is a group of individuals with exposure and a group without exposure followed over time to compare disease occurrence and a case control study is individuals with a disease compared with similar individuals with the disease to determine association of disease with prior exposure.

2x2 risk ratio table formula

Horizontal: exposure
No exposure

Across: Disease | no disease | total