Epidemiology Flashcards
Finals review
What is epidemiology
The study of the distribution and determinants of a disease frequency in human
What is epidemic outbreak?
The occurrence of a disease in a population that exceeds the usual or expected number of cases.
What is a pandemic?
Disease the occurs thought the population of the country, people or the world
What are some purposes of epidemiology?
( QIPM)
- Quantify the magnitude of health problems
- identify the factors that cause disease
- providing quantitative guidance
- monitor the effectiveness of prevention strategies
History = Who is also known as the father of medicine? What did he do?
Hippocrates = 5th century
- > suggested that human diseases might be a result of external and personal environment of an individual
History = What did John Graunt do in 1662?
- First person to quantify patterns of disease
— noted
—– # of men born or dead
—– high infant mortality
—– Mortality rate due to seasonal variation
History = William Far( 2 centuries later), who is he, what did he do?
- 1839
— setup system to regularly track death numbers and causes, comparing mortality rates based on various factors.
History = John snow, what did he do?
- Formulated and testes hypothesis concerning origin of cholera epidemic
Cholera:
—- acute bacterial infection of small intestine
What did John snow found about cholera?
- from the data, he found out that cholera transmitted though contaminated water
- charted frequency and distribution of water
- Identify the causes of cholera
What are the components if epidemiology principles and the methids?
- Distribution ( when? where who?
—— Comparisons between population at a given time /CAUTIONS BCS - allowing to make hypothesis - disease frequency
—— Quantification of the existence of a disease / CAUTIONS BCS - aids for investigations of diseases occurrence - Determinants of disease
——- distribution + disease frequency / CAUTIONS BCS - necessary to test epidemiologic hypothesis - Hypothesis
—– Statement that is done from a theory that predicts teh relationship amount variables - Assumptions
—– Judgments that are not true about t.
Some Key assumption of epidemiology include:
- Majority of human diseases does not occur random
- Casual and preventative factors for diseases can be identified though observing populations
What re some primary units of concern?
- Groups of persons = is not separate individuals
- They must be studied so that they can answer question relating to the ethiology( a study that determined origin of a disease)
What are some key concepts of Epidemiology?
- Quantitative science
# Measured quantities - Count
# number of persons in the group studied who have particular diseases - Ratio
# relationship with 2 numbers - Proportion
# expressed in % and the numerator is a part of denominator - Rate { Prevalence “one specific time”, Incidence}# Prevalence rate = preexisting cases of a condition with a specific time , denominator = everyone in the population# Incidence rate = # of new cases of a particular conditions.
Incidence rate how to calculate?
number of NEW cases of a particular
disease or condition COMMENCING
during a specified period of time
___________________________ x 100
population - pre-existing cases
(this becomes the population at risk)
- population at risk is the population minus the number of people who have already contracted the disease or condition.
This is bacause you want to now the new cases not the old ones.
Prevelance rate how to calculate?
Prevalence Rate =
number of cases of particular disease or condition existing in a population at a specified period of time \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ x 100 population (everyone is included!)
What are the 2 epidemiologic Study designs?
- Descriptive studies
- Analytic studies
What is descriptive study design?
- Study design that asks WHO?, WHERE? WHEN?
- This type of study will ,aid the development of epidemiologic hypothesis.
- Useful for developing and crudely testing initial hypothesis
- include 2 types:
1. x- sectional
2. Ecologic
X-sectional design of descriptive stuides?
- Measure cause and effect at a certain point
Advantages include:
- Looking to individuals rather than groups
- easy control for confounding variables
Limitations:
- Outcome and exposure measured at the same time
- Cannot make statements about cause and effects
- cannot examine longitudinal relationships
Ecological design of descriptive studies?
- Use existing data to compare disease rates based on specific characteristics of a population.
Advantages:
- inexpensive
- relatively easy to complete
limitations:
- analysis on population not individual
- no control over effects of other factors
- Can produce “ spurious” results
What is Analytics study design?
- Focus on testing hypotheses from descriptive studies to find out if a factor causes or prevents a disease
- Include 2 types:
- Cohort studies (Prospective studies)
- Case control studies (retrospective studies)
What is the cohort studies of analytic study design?
A cohort study starts with a group of people who are initially disease-free and follows them over time. It aims to:
--- Determine how exposure to a factor (Y) affects the rate of a disease (X).
--- Establish cause and effect relationships.
--- Account for varying exposure levels among individuals. though different groups of people.
What are the advantages of the cohort study?
- temporal sequence = you know exactly the time between the exposure and the outcome
- Good for rare exposure
- Good for understanding multiple effects of a single exposure
What are some limitation of the cohort study?
- Difficult to do due to Large N
- Costly = due to Large N
- Loss to follow up
Some diseases are rare so it is difficult to get a sufficient number of cases for analyses.
How does the selection for cohorts take place?
- Accessibility
- History of previous exposure
- medical records
What is the Case-Control Studies of analytic study design?
Retrospective studies compare two groups:
- Cases: People with the disorder (X). - Controls: People without the disorder. They analyze differences in past exposure to factor Y.
How do Case-Control studies select cases?
- physicians
- employers
- healthcare providers
- medical records
- Death records
- subjects themselves
- Proxies for the subject
What are the advantages Case control study?
- Result in short period of time
- Efficient for studying rare diseases.
- enable hypothesis testing
- used to aquaire greater detail about the exposure.
What are the limitations for Case control study?
- may be influenced by recall bias –> exposure information is obtained after the disease has been diagnosed
- May result in selection bias —> can be challenging to recruit appropriate control group (can therefore affect the odds ratios)
What are some error in Data collection?
- Clinical observations (diseases presence/ absence)
- disease reporting
- clinical diagnosis
- Death certificated and mortality statistics
- Medical chart review( missing information, illegible notes)
- Laboratory data
- Responses to questionnaire
How to establish causation?
- Temporal sequence
- consistency
- strength of association
- specificity of effect
- biological gradient
- existing data and theory
What are problems of error?
- Bias –> selection, information, confounding
- Random variation:
- chance differences between groups
- Random misclassification:
- subject in the wrong group
What are some ways to control Errors?
- matching
- homogeneous grouping
- Stratified sampling
- post-stratification
