WEEK THREE Flashcards

1
Q

What is epidemiology

A

-the study of disease patterns and transmission

Epidemiology is concerned w/ the distribution and determinants of health and diseases, morbidity, injuries, disability and mortality in populations

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2
Q

Fields in which epidemiologists have some knowledge of ?

A
  • public health (disease prevention)
  • clinical medicine (disease classification and diagnosis)
  • pathophysiology (understand basic biological mechanisms)
  • biostatistics (quantify disease frequency)
  • social sciences (understand social context in which disease occurs )
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3
Q

Who is Barry Marshall

A
  • internist who together w/ collaboration w/ Robin Warren, discovered H. Pylori was consistently present in biopsies from ulcer patients
  • started successfully treating patients w/ antibiotics
  • won Nobel prize
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4
Q

What is a classic case example of epidemiology?

A
  • cholera
  • cause: vibrio cholera bacterium
  • mid 19th c. Outbreak in London
  • John Snow believed outbreak was spread by contaminated water
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5
Q

Who was john snow

A

1813-1858
English anesthesiologist who innovated several key epidemiological methods that remain today

“Father of epidemiology”

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6
Q

1900 main causes of death in US

A

Influenza and pneumonia
Tuberculosis
GI infections
Heart disease
Cerebrovascular disease

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7
Q

1950 main causes of death in US

A

Heart disease
Cancer
Cerebrovascular
Disease of early infancy

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8
Q

2010 main causes of death in USA

A

Heart disease
Cancer
Chronic airway disease

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9
Q

What is epidemiological transition

A

Describes a shift in the patterns of morbidity and mortality from causes related primarily to infectious and communicable diseases to causes associated w/ chronic, degenerative diseases

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10
Q

What is demographic transition

A

Shift from high birth rates and death rates found in agrarian societies to much lower birth and death rates in developed countries

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11
Q

Define distribution

A

Distribution implies that diseases do not occur randomly

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12
Q

What are determinants

A

Factors that can cause a change in a health condition or outcome

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13
Q

What is morbidity

A

Illness due to a specific disease or cause

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14
Q

What is mortality

A

Death due to a specific disease or cause

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15
Q

Define endemic

A

The habitual presence of a disease within a given geographical area

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16
Q

What is an epidemic

A

The occurrence of an infectious disease in excess of normal expectancy and generated from a common or propagated source

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17
Q

Examples of endemics

A

Plague among rodents in AZ
Rabies in several animal species in US
Valley fever (coccidioidomycosis) is an endemic in AZ

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18
Q

Examples of epidemics

A

Upper respiratory infections
Human rabies
Outbreak of vibrio infections following hurricane Katrina

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19
Q

Examples of pandemics

A

COVID19
1918 influenza
HIV/AIDS

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20
Q

What is a sporadic disease, examples?

A

Disease occurring singly, widely scattered, not an epidemic or endemic

Human rabies
CJD (creutzfeldt-Jakob disease)

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21
Q

What are the phases of natural history of disease

A

Preclinical phase
Clinical phase

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22
Q

Exposure to pathogen and biological onset of disease occurs during what phase of disease

A

Prior to preclinical phase

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23
Q

The preclinical phase begins with the _______ and ends with ?

A

Preclinical phase begins w/ biological onset of disease and ends when symptoms appear

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24
Q

What occurs during the clinical phase

A

Diagnosis and therapy begins

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25
Q

Who was Robert Koch?

A

1843-1910 German physician
- Koch’s postulates demonstrated the association b/w a microorganisms and a disease

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26
Q

What are Koch’s postulates?

A
  1. Organism must be observed in every case of the disease
  2. Must be isolated and grown in pure culture
  3. Pure culture must, when inoculated into a susceptible animal, reproduce the disease
  4. The organism must be observed in, and recovered from, the experimental animal
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27
Q

Who was Sir Austin Bradford Hill and what is he known for?

A

English epidemiologist
Developed Hill’s criteria for causation in 1965

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28
Q

What are Hill’s 9 criteria for causation

A
  1. Strength
  2. Consistency
  3. Specificity
  4. Temporality
  5. Biological gradient
  6. Plausibility
  7. Coherence
  8. Experiment
  9. Analogy
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29
Q

What is temporality in Hill’s criteria for causation

A

The cause (exposure) must be observed before the effect

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30
Q

What is biological gradient in Hill’s criteria for causation

A
  • AKA dose-response, shows a linear trend in the association b/w exposure and disease
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31
Q

what is plausibility in Hill’s criteria for causation

A

The association must be biologically plausible from the standpoint of contemporary biological knowledge

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32
Q

What is the epidemiological triangle

A

A model used to describe the etiology of infectious diseases

3 major factors: agent, host, environment

Affected by: time, transmission types, vectors of vomîtes

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33
Q

What is a dose response curve

A

Type of correlative association b/w an exposure and effect

Threshold refers to the lowest dose at which a particular response occurs

Ex: dose-response relationship b/w the # of cigs smoked daily and mortality from lung cancer

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34
Q

What is an epidemic curve

A

Graphic plotting of the distribution of cases by time of onset

Helps in identifying the cause of a disease outbreak

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35
Q

What is internal validity

A

The degree to which a study has used methodologically sound procedures

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36
Q

what is external validity

A

One’s ability to to generalize the results of the study

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37
Q

what is the definition of error

A

Difference b/w the value obtained and the true value for the population

Two categories: sampling error and non-sampling error

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38
Q

What is sampling error

A

Variation that occurs because we are studying a sample rather than an entire population

Even if samples are chosen properly and are representative of the population, there will always be natural variation b/w diff samples

Can be quantified

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39
Q

What are measurements to express sampling error

A
  • confidence intervals
  • standard error
  • margin of error
  • coefficient of variance
40
Q

What is non-sampling error

A

Errors that are a result of factors other than using a sample

Result in bias

41
Q

What types of bias may impact epidemiological studies

A

Bias = systematic deviation of results or interferences form truth

Recall bias
Selection bias
Observer bias
Confounding bias

42
Q

Can bias be measured

A

No

43
Q

How to control for recall bias

A

Be aware of limitation when selected study method

44
Q

How to control for observer bias

A

Blind or double blind
Script
Multiple observers

45
Q

How to control for selection bias

A

Randomization

46
Q

How to control for confounding bias

A

Design phase: think through professional con founders
Analysis phase: some types of analysis can control for confounders

47
Q

The field of descriptive epidemiology classifies the occurrence of disease according to what variables

A

Person (who is affected)
Place (where condition occurs)
Time (when and over what time period condition has occurred)

48
Q

What is a case report

A

In depth study of one case
No comparison group

49
Q

what is a case series

A

Three or more cases involving patients given similar treatment
No comparison group

50
Q

What is a cross-sectional study

A
  • Looks at data at a single point in time
  • Participants are not selected based on outcome or exposure, just based on inclusion/exclusion criteria
51
Q

what is an ecological study

A

A special kind of cross-sectional study

  • units of analysis are populations or group of people rather than individuals
52
Q

What are some examples of ecological studies

A
  • incidence of disease post vaccination programs
  • how tobacco taxes affect tobacco use
  • certain occupations and hearing loss
  • cancer rates and dietary practices
53
Q

What is ecological fallacy

A

Associations observed at group level do not necessarily hold true at the individual level

54
Q

“ there are both high levels of toxic pollution and cancer in norther NJ, therefore toxins are causing cancer”

Is an example of…?

A

Ecological fallacy

55
Q

What does COUNT refer to as an epidemiological measure

A

Refers to the number of cases of a disease or other health phenomenon being studied

56
Q

What is a proportion

A

Comparison of a part to the whole

Type of ratio in which the numerator is part of the denominator

Application: proportion of deaths among men, proportion of lung cancer due to smoking

Ex: arrack rate, point prevalence

57
Q

What is a rate

A

Compares two numbers

-measure of frequency where event occurs in a defined population over a specific period of time

  • way of standardizing in order to make a fair comparison
58
Q

What is population at risk

A

Members (human or animal) of the overall population who are capable of developing the disease of condition being studies

Usually identified as the denominator in rate calculation

59
Q

What are the 3 types of rates

A

Crude rate
Specific rate
Adjusted rate

60
Q

What is crude rate

A

Summary rate based on the actual number of events in a population over a given time period

*incidence, prevalence, morbidity, mortality

61
Q

What is specific rate

A

Based on a particular subgroup of the population defined

*cause, age, proportional mortality rate

62
Q

What is adjusted rate

A

Measures where statistical procedures have been applied to remove the effect of differences in population distributions

  • standardized mortality rate
63
Q

What does prevalence measure

A

The number of affected persons
Number of persons w/ disease of interest
Number of cases/number of people in the population

64
Q

What is incidence

A

Number of new cases of disease during a specified time period

Number of new cases/number of persons in population

65
Q

What are factors that cause prevalence to increase

A
  • increases in incidence
  • longer duration of the case
  • in migration of cases
  • prolongation of life patients w/out a cure
66
Q

What are factors that cause prevalence to decrease

A
  • decreases in incidence
  • shorter duration of disease
  • influx of healthy people into population
  • improved cure rate
67
Q

What is the numerator and denominator of morbidity rate

A

Numerator = total # of illnesses in a population over a specialized period of time

Denominator = average population at risk over same time period

68
Q

What is the numerator and denominator of mortality rate

A

Numerator = total # of deaths in population over a specified time

Denominator = average population at risk over same time period

69
Q

What is the direct method of adjusted rates

A

Used when you know the age-specific rates of mortality or morbidity in all the population under study

70
Q

What is the indirect method of adjusted rates

A

Only need to know the total number of deaths or cases and the age structure of the study population

Preferable when there are small numbers in particular age groups

71
Q

What are limitations associated w/ adjusted rates

A

Adjusted rates are artificially created so they can
- lead to misinterpretation
- based on assumptions
- should only be compared to another rate that was computed the same way

72
Q

What is descriptive analytical epidemiology

A
  • used when little is known about the disease
  • relies on preexisting data
  • who, when, where
  • illustrates potential associations
73
Q

What is analytical epidemiology

A
  • used when insight about various aspects of disease is available
  • rely on development of new data
  • why
  • evaluates the causality of associations
74
Q

What is the Odds Ratio

A

Measure of the association b/w exposure and outcome in CASE CONTROL STUDIES

provides a rough estimate of relative risk

75
Q

what is relative risk

A

used when comparing outcomes of those who were exposed to something vs those who were not exposed

used in cohort studies and randomized clinical trials

76
Q

what is a cross over study

A

groups get switched, reduces variation b/w groups

77
Q

what is a community trial

A

looks at how intervention affects the population in the community

–> behavioral change at the population level

ex: water fluorination
smoking cessation campaigns

78
Q

what does an Odds Ratio (OR) = 1 mean

A

exposure doesn’t affect odds of outcome

79
Q

what does OR >1 mean

A

exposure is associated w/ higher odds of outcomes

80
Q

what does OR < 1 mean

A

exposure is associated w/ lower odds of outcome

81
Q

what is sensitivity

A

% truly positive (a/a+c)

82
Q

what is high sensitivity?

A

high confidence that an animal w/ a negative test does NOT have the condition

can trust that negative test result b/c false negatives are low

83
Q

what is specificity

A

% truly negative (d / b+d)

84
Q

what is high specificity?

A

high confidence that an animal w/ a positive test result actually has the condition

85
Q

how can sensitivity be improved?

A

parallel testing = running different tests simultaneously

(+) if either or both tests are positive
( - ) if both tests -

proves you DONT have the disease

86
Q

how can specificity be improved?

A

serial testing: running one test after another
- run screening tests then a confirmation test

if confirmation test is +, disease present
if confirmation test is -, test is negative

proves you DO have the disease

87
Q

what is positive predictive value

A

what are the chances a positive result is truly +

as disease prevalence decreases, positive predictive value also decreases

88
Q

Likelihood ratio

A

incorporates the probability that the test is positive in patients w/ and w/out the disease

89
Q

what is a positive likelihood ratio

A

probability that the test is (+) in patients w/ disease / prob. that test is (+) in patients w/out diseasse

90
Q

what are the 2 models for multifactorial causality?

A
  1. epidemiologic triangle
  2. web of causation
91
Q

when assessing disease association and causality, how can chance be ruled out

A

statistical procedures may be used to employ the degree to which chance may have accounted for association

but chance can never be completely ruled out

92
Q

what plot type is this

A

dose response curve

93
Q

what plot type is this

A

epidemic curve
aids in identifying the cause of outbreak

94
Q

what type of error results in bias

A

non-sampling errors

95
Q

is bias typically more prevalent in analytical or descriptive studies

A

analytical