HOSA EPIDEMIOLOGY EVERYTHING

Descriptive Epidemiology

deals with the frequency and the distribution of risk factors in populations and enables to assess the extent of a disease. It can thus provide hypotheses of etiologic research

Analytical Epidemiology

aims to research and study risk and protector factors of diseases.

Pandemic

An epidemic occurring worldwide, or over a very wide area, crossing international boundaries, and usually affecting a large number of people.
Ex.. 1918 influenza (Spanish flu)

Distribution

The occurrence of diseases and other health outcomes varies in populations, with some subgroups of the populations more frequently affected than others.

Epidemic

sudden increase in occurrence of disease in a population
usually within a specific geographic region or population

Exposures

Related to determinants,which pertain either to contact with a disease-causing factor or to the amount of the factor that impinges upon a group or individuals.

Determinants

determinants Any factor that brings about change in a health condition or other defined characteristic.

Morbidity

illness due to a specific disease or health condition

Mortality

Death, usually on a large scale

Quanification

Refers to counting the cases of illness or other health outcomes. Denotes the use of statistics to describe the occurrence of health outcomes and measure their association with exposures

Hippocrates

departed from superstitious reasons for disease outbreaks Wrote On Airs, Waters, and Places in 400 BC
Suggested disease might be associated with environmental factors

John Snow

(1813-1858)An English anesthesiologist who innovated several of the key epidemiologic methods that remain valid and in use today
Believed that cholera was transmitted by contaminated water and was able to demonstrate this association.

Paracelsus

(1493-1541) was one of the founders of the field of toxicology.
The dose-response relationship
The notion of target organ specificity of chemicals

John Graunt

is considered by many historians to have founded the science of demography, the statistical study of human populations. He analyzed the vital statistics of the citizens of London and wrote a book regarding those figures that greatly influenced the demographers of his day.

Ramazzini

(1633-1714) is regarded as the founder of the field of occupational medicine.
He authored De Morbis Artificum Diatriba (Diseases of Workers), published in 1700.

Edward Jenner

(1749-1823) developed a method for smallpox vaccination in 1796.

William Farr

(1807-1883)Appointed "Compiler of Abstracts" in England, 1839
Developed a more sophisticated system for codifying medical conditions
Examined possible linkage between mortality rates and population density (defined as number of persons per square mile)

Robert Koch

(1843-1910), a German physician
Published Die Aetiologie der Tuberkulose in 1882
Koch's postulates demonstrated the association between a microorganism and a disease.

Alexander Flemming

(1881-1955) discovered the anti-microbial properties of the mold Penicillium notatum in 1928.
Antibiotic became available toward the end of World War II

carrier

individual - potential source of infection for others

can be infected or transferring from infected person to another

etiologic agent

etiologic agent pathogen responsible for diseas

reservoir

primary habitat which the agent is normally found and from which infection may result

vector

living transmitters of pathogen

vehicle

non-living transmitters

sporadic

disease occurs at irregular intervals and in unpredictable locations

endemic

maintained at steady frequency over long period in a particular population or geographic location

direct horizontal transmission

person to person (shaking hands, kissing)
self to self (direct fecal-oral- not washing hands)

direct vertical transmission

parent to child (sperm, egg, across placenta, breast feeding, birth canal)

waterborne vehicle

generally do not grow, but can survive in contaminated or inadequately treated or untreated water

airborne

pathogen travels through air

fomite

non-living object
harbors and transmits an infectious agent

Pathology

Study of diseases

Bias

A flaw in either the study, design, or data analysis that leads to an erroneous result.

Case Fatality Rate (CFR)

A mathematical quantity that describes the severity of a disease; usually applied to acute diseases. It is the proportion of persons diagnosed with a disease who actually die from the disease during the period of observation.

CFR Formula

# dying from disease Y in population P
--------------------------------
# with disease Y in population P

Comparison of Rates

A measure of incidence or occurrence of a disease in a population.

Rate Difference Formula

(rate of disease Y among those exposed to X) - (rate of disease Y among those NOT exposed to X)

Relative Risk Formula

Rate of Y among those exposed to X
----------------------------------
Rate of Y among those NOT exposed to X

Incidence Formula

# develop disease Y in pop. P in time T
--------------------------------
# in pop. P

Precision

Refers to the degree to which there is variation in a measurement.

Accuracy

Refers to the degree to which the measurement is, on average, correct.

Population Controls

Serve as the references against which cases are compared.

Mortality

Refers to death; death rates.

Morbidity

used to refer to illness; rates of illness.

Exposure

Generic term for the effective presence of any agent or factor that is thought to cause a disease.
Ex: toxic chemical, dietary habits, activity levels, microorganisms.

Endemic

Baseline incidence rate in a pop; at ay point in time, people are acquiring a given disease in the pop.
Ex: flu rate

Epidemic

A greater incidence of the disease in a pop. than would normally have been expected; greater than endemic or baseline incidence.

Disease Transmission

Describes the process of the spreading of a disease through a population;
"Who got it & how did it spread?"

Contingency Table

Often used to show the relationship between disease and exposure; used to divide persons into the categories of diseased & exposed (A), diseased & NOT exposed (B), NOT diseased & exposed (C), NOT disease & NOT exposed (D).

Contingency Table Example

Exposure
| | YES | NO |
Disease| YES | A | B |
| NO | C | D |

Confounding

A "mixing of effects;" When a factor (X) causes disease (Y), that relationship could be confounded by a factor (C), that is associated with both X & Y.
C could also be an alternative explanation for the relationship between X & Y.

Conditional Probability

The probability of an event given the occurrence of another event; the probability of disease (Y) given exposure to factor (X).

Prevalence

A mathematical quantity that describes the presence of a disease (Y) in a population (P); proportion of persons in the population (P) with disease (Y).

Prevalence Formula

# with Y in P
------------
# in P

Incidence

A mathematical quantity that describes the occurrence of a disease (Y) in a population (P); proportion of persons in the pop. (P) who newly develop the disease (Y) within a given time period (t).

Incidence Formula

# who develop Y in P at a given time (t)
---------------------------------
# in P

Racial & Ethnic Health Disparities

Used to describe differences in disease rates by rates or ethnicity.
Ex: sickle cell anemia in African Americans

Relative Risk

aka (MA): Common Measures of Association; any mathematical measure that is used to quantify the association between two or more variables.

Attributable Risk (AR)

a group of measures which describe the amount of disease risk that can be attributed to a given factor (X).
Ex: Attributable Fraction

Attributable Fraction (AF)

the proportion of disease (Y) in the population (P) that can be attributed to factor (X).

AF Formula

[(incidence in P)-(incidence in unexposed)]
-----------------------------------
(incidence in P)

Screening

the process of early diagnosis of a disease; identification of disease or risk factors for the disease in its pre-symptomatic or pre-clinical stage.
Ex: cervical cancer screening.

Incidence

The number of new cases per person per unit of time

Prevalence

The proportion of the population at a given time that has a case

Case Fatality Rate

Ratio of fatal cases to total cases

Risk factor

A definable element of exposure that captures at least one part of the pathway by which the cause increases the risk that a member of the population will meet the criteria of a case.

Observational Study

Study in which events occur without the scientist having controlled starting conditions. Resembles the studies of geology and astronomy.

Epidemiology

The study of the distribution and determinants of health-related states or events in specified populations, and the application of this study is the control of health problems.

5 Ws of Descriptive Epidemiology

Diagnosis or health event (what), Person (who), Place (where), Time (when) and Modes of Transmission (why/how)

Frequency

Not only the number of health events, but also the relationship of that number to the size of the population.

Pattern

The occurrence of health-related events by time, place and person.

Descriptive Epidemiology

Characterizing health events by time, place, and person.

Determinants

The causes and other factors that influence the occurrence of disease and other health-related events.

Analytic Epidemiology

Provides the "why" and "how" disease and other health events spread/occur.

Public Health Surveillance

The ongoing, systematic collection, analysis, interpretation, and dissemination of health data to help guide public health decision making and action.

Field Investigation

Characterizes the extent of the epidemic and attempts to identify its cause.

Shoe Leather Epidemiology

Slang; the objective is to learn more about the natural history, clinical spectrum, descriptive epidemiology, and risk factors of the disease before determining what disease intervention methods might be appropriate.

Analytic Studies

A study with the purpose of identifying and quantifying the relationship between an exposure and an outcome and to test hypotheses about causal relationships by comparing case-patients and those in an appropriate comparison group (control).

Design

Includes determining the appropriate research strategy and study design, writing justifications and protocols, calculating sample sizes, deciding on criteria for subject selection (e.g., developing case definitions), choosing an appropriate comparison group, and designing questionnaires.

Conduct

Involves securing appropriate clearances and approvals, adhering to appropriate ethical principles, abstracting records, tracking down and interviewing subjects, collecting and handling specimens, and managing the data.

Analysis

Begins with describing the characteristics of the subjects. It progresses to calculation of rates, creation of comparative tables (e.g. two-by-two tables), and computations of measures of association (e.g., chi-square test), confidence intervals, and the like.

Interpretation

Involves putting the study findings into perspective, identifying the key take-home messages, and making sound recommendations. Doing so requires the epidemiologist be knowledgeable about the subject matter and the strengths and weaknesses of the study.

Evaluation

The process of determining, as systematically and objectively as possible, the relevance, effectiveness, efficiency, and impact of activities with respect to establish goals.

Effectiveness

Refers to the ability of a program to produce the intended or expected results in the field.

Efficacy

The ability to produce results under ideal conditions.

Efficiency

Refers to the ability of the program to produce the intended results with a minimum expenditure of time and resources.

Formative Evaluation

Evaluation that focuses on plans.

Process Evaluation

Evaluation that focuses on operations.

Summative Evaluation

Evaluation that focuses on impact.

Linkages

Working in conjunction with members of other disciplines.

Case Definition

A set of standard criteria for classifying whether a person has a particular disease, syndrome, or other health condition.

Rate

The number of cases divided by the size of the population per unit of time.

Secular trends

Long term trends; Assess the prevailing direction of disease occurrence (increasing, decreasing, or essentially flat).

Epidemic Curve

A graph used to show the time course for a disease outbreak or epidemic.

Experimental Study

In this type of study, the investigator determines through a controlled process the exposure for each individual (clinical trial) or community (community trial), and then tracks the the individual or communities over time to detect the effects of the exposure.

Cohort Study

In this type of study, and epidemiologist records whether each study participant is exposed or not, and then tracks the participants to see if they develop the disease of interest. Similar to an experimental study, but observes rather than determines the exposure status.

Prospective Cohort Study

A kind of cohort study that observes the exposure status, and tracks the participants to see if they develop the disease in question; Also called a follow-up study

Retrospective Cohort Study

In this type of study, both the exposure and the outcomes have already occurred.

Case-Control Study

In this type of study, epidemiologists start by enrolling a group of people with a disease and a group of people with out that disease (controls). Investigators then compare previous exposures between the two groups.

Case-Patient

A person with the disease of interest. Not called a case because case refers to occurrence of disease rather than a person.