EPI test 1

What is disease frequency?
quantifying how often a disease arises in a population

What is disease distribution?
the analysis of disease patterns according to the characteristics of person, place, and time. Who is getting the disease, where it is occurring. and how it is changing over time.

What is public health?
multidisciplinary field whose goal is to promote the health of the population through organized community efforts.

What is the main goal of public health?
disease prevention

What is basic research?
studies cells, tissues, & animals in a laboratory setting usually focused on disease mechanism/process. Examples: immunology, toxicology

What is clinical research?
focuses on disease diagnosis/prognosis & treatment. Based on people who come to a medical care facility. Examples: pediatrics, internal medicine

What is public health research?
studies populations or communities at large. Example: epidemiology

What is epidemiology?
the study of the distribution and determinants of disease frequency in human populations and the application of this study to control health problems

Key words: population, disease frequency, disease distribution, disease determinants, disease

Who is John Snow?
(1813-1858) Snow used data obtained by Farr to conduct a study for the Broad Street cholera epidemic, proved cholera was transmitted by fecal contamination of drinking water.

What is a population?
Group of people with a common characteristic. Ex. Age, residence, or the occurrence of an event.

What is incidence?
measures occurrence of new disease; captures the transition from health to disease

What is cumulative incidence?
defined as the proportion of a candidate population that becomes diseased over a specified time period. Average risk of getting a disease over a period of time. Numerator (number of new cases of disease) Denominator (population at risk). Proportion can be expressed as a percentage. Usually used in fixed populations.

What is incidence rate?
defined as the occurrence of new cases of disease that arises during person-time of observation. Numerator (number of new cases of disease) /Denominator (person-time of observation in candidate population). Used for dynamic populations.

What is prevalence
Measures the proportion of the total population that is diseased at a point in time
Numerator (number of existing cases) /Denominator (total population)

What is a cohort study?
healthy subjects are defined according to their exposure status and followed over time to determine the incidence of symptoms, disease, or death. The common characteristics for grouping the subjects is their exposure level.

What are observational studies?
Studies causes, preventions, and treatments for diseases; investigator passively observes as nature takes its course. NO INTERVENTION.

What is an experimental study?
Studies in which all of the risk factors are controlled by the investigator. Purpose is to study preventions and treatments for diseases. Investigators manipulates which groups receive the agent under study

What are the four types of observational studies?
Cohort, Case-Control, Cross-Sectional, Ecological

What are the descriptive observational studies?

What is a descriptive study?
investigates the distribution of disease (occurrence)

What is an analytical study?
investigate the determinants of disease

What is the formula for prevalence?
= Incidence rate x Duration of disease

What are the main objectives of epidemiology?
1)study the natural course of disease from onset to resolution
2)determine the extent of disease in a population
3)identify patterns and trends in disease occurrence
4)identify the causes of disease
5)evaluate the effectiveness of measures that prevent and treat disease

What is the domain of descriptive epidemiology? What characteristics are analyzed?
Distribution of disease.
Person, Place, Time.

What are the types of descriptive studies? (4 Cs)
1) Case Reports
2) Case Studies
3) Correlational Studies
4) Cross-sectional studies

What are Case reports/case studies?
Describes experience of single patient or group of patients

What is a disease cluster?
aggregation of relatively uncommon events or disease in space and/or time in amounts that are believed or perceived to be greater than could be expected by chance.

What are the main purposes of descriptive epidemiology?
examine distribution of disease and to generate specific hypothesis about the causal relationships

What is a correlational/ecological study?
Compare disease frequencies from entire populations based on some factor of interest. Different groups over same time period
Same group over different time periods.

What are the strengths of a correlational/ecological study?

What are the limitations?

Quick, inexpensive, can utilize existing data

Provide data on populations not individuals, cannot control for all differences among populations

What is a cross-sectional study?
“Am I like my neighbors?” study compares groups in terms of their current health and exposure status and assesses their similarities.

What is a cohort study?
Typically examines multiple health effects of an exposure; subjects are defined according to their exposure levels and followed for disease occurrence.

What is a case-control study?
the “why me?” study investigates the prior exposure of individuals with a particular health condition and those without it to infer why certain subjects, the “cases,” become ill and others, the “controls,” do not.

What is a ecological study?
examines relationship between exposure and disease with population-level rather than individual-level data.

What are the strengths of a cross-sectional study?


Exposure and disease data from individuals
Provide important data for public health planning
low cost! and generalizability!

No temporal sequence between exposure and disease
Assess prevalence of disease

What are crude rates?
A summary measure calculated by dividing the total number of cases in the population by the total number of individuals in that population at a specified time period
i.e. crude death rates

How do you calculate crude death rate?
total number of deaths / total population

How do you calculate age-adjusted rates?***

What are the Observational Analytic studies?
case-control and cohort

What are the experimental analytic studies?
clinical trials

What are case-control studies?
Study subjects SELECTED based on disease
Then obtain exposure history

Strengthes of case-control studies?


Efficient, inexpensive, Good for rare diseases, multiple exposures

Temporal sequence
Control selection
Information bias

What are cohort studies?
The “What will happen to me?” study follows a group of healthy people with different levels of exposure and assesses what happens to their health over time.
Disease-free subjects selected and classified based on exposure, follow subjects through time.

What is a retrospective cohort?
Historical records
Everything has happened already

What is a prospective cohort?
Nothing has happened yet! Gunna follow them through the future!

Strengths of cohort studies?


Maintain temporal sequence, Direct estimate effect, Good for rare exposures, multiple outcomes

Expensive, Take a long time, Require a large study size, Exposure can change

What are clinical trials?
A controlled study involving human subjects, designed to evaluate prospectively the safety and effectiveness of new drugs or devices or of behavioral interventions.

Strengths of clinical trials?


“Gold standard”

Costly, Time consuming

correlational studies?
population comparisons

strengths of cross-sectional studies?
The main advantage is that the study is a particularly easy study to conduct, as we do not have to wait for the health outcome to occur or estimate what the level of exposure was likely to have been years ago. Its main disadvantage is that a cause can’t be inferred, because only current health and exposure are being studied.