Lecture 10 - Epidemiologic Principles And Methods Flashcards
(119 cards)
1
Q
Epidemiology is defined as the ___ and ____ of disease frequency in human populations
A
distribution and determinants
2
Q
The epidemiologist must….
A
define the disease in a clear way
3
Q
Why must the epidemiologist define the disease in a clear way?
A
so that there is no doubt about whether an individual case should be counted
4
Q
Is hepatitis easy to identify? why or why not?
A
not easy to identify because the symptoms are fairly nonspecific
5
Q
if a patient comes into the ER with vomiting and diarrhea, how do the drs determine if it’s hepatitis?
A
a blood test for liver function is conducted
6
Q
How is “disease frequency” measured?
A
-count the # of cases
-relate that # to the size of the population, yielding a RATE
7
Q
What are the 2 kinds of frequency measures used in epidemiology?
A
incidence rates
prevalence rates
8
Q
What is incidence rate?
A
the rate of new cases of a disease in a DEFINED population over a DEFINED period of time
9
Q
Incidence measures the probability that….
A
probability that a healthy person in that population will develop the disease during that time
10
Q
incidence rates help to identify the…
A
cause of disease
11
Q
give an example of how incidence rates help to identify the cause of disease
A
incidence of birth defects in europe rose dramatically after the indroduction of thalidomide - a drug used as a sleeping pill
12
Q
What is the prevalence rate?
A
the total number of cases existing in a defined population at a SINGLE POINT IN TIME
13
Q
How is prevalence generally measured?
A
by doing a survey
14
Q
How are incidence and prevalence related to each other?
A
relationship depends on how long people live with the disease
15
Q
Give an example of when the PREVALENCE would be much higher than the INCIDENCE
A
in chronic diseases that are not lethal.
ex: arthritis
16
Q
which are more useful in epidemiologic studies - incidence rates or prevalence rates? why?
A
incidence rates because prevalence rates change slowly
17
Q
What rate is often used as a measure of frequency for diseases that are usually fatal?
A
death rates
18
Q
for most lethal diseases such as pancreatic cancer, death rates are close or far from incidence rates?
A
close
19
Q
since death rates and incidence rates are close, what does this mean?
A
almost all people who get the disease die
20
Q
For diseases in which many people survive, what can you say about the relationship between the MORTALITY(death) RATE and the INCIDENCE RATE?
A
mortality rate will be much smaller than the incidence rate
21
Q
When are death/mortality rates valuable?
A
when death due to a disease/event IS POSSIBLE
22
Q
Give a specific example of when a death rate would be not useful
A
death rates for arthritis
23
Q
Give a specific example of when a death rate WOULD be useful
A
comparing death rates in high-speed accidents vs low speed accidents
24
Q
the ______ of a disease is the answer to the WHO, WHERE, AND WHEN of the illness
A
distribution
25
"WHO" characterizes....
the disease victims by factors such as age, sex, race, and economic status
26
Give an example of the WHO
cancer and heart disease is more common in older people
measles and chicken pox in younger and unvaccinated
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"WHEN" looks for.....
TRENDS in disease frequency over time or during a specific time period or event
28
the ________ of lung cancer has been increasing in the US since the 1930s
INCIDENCE
29
Epidemiologist construct______
epidemic curves
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What do epidemic curves show?
the number of cases over a defined period of time
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epidemic curves answer the ____ question
WHEN
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The WHERE question looks at.....
comparisons of disease frequency in different countries, states, counties, or other geographic divisions. comparison btwn URBAN and RURAL populations
33
Give an example of a hypothesis that arose because of WHERE question
observation that dental cavities were less common in children who lived in parts of the country that had high concentrations of fluoride in the water
34
Statistics on cause of death in different countries can help to.....
generate hypotheses as to causes of disease
35
What did people hypothesize were some potential causes of death from heart disease due to the death statistics on heart disease?
heart disease was due to...
-the pressure of urban life
-diet
36
Give an example of how information on the distribution of a disease leads to clues to determinants of that diseae
international comparisons of cancer mortality have lead to hypotheses about the various kinds of cancer--
-cancer of the colon and rectum is more common in industrialized countries than developing countries
-Maybe diet is involved
-americans eat meals rich in fat, meat and dairy
-chinese diets are high in fiber and vegetables
-people who move from low rate countries to high rate countries - they have higher rates of disease because they acquire habits of the host
-Japan rates of colorectal cancer have more than doubled since the 50s - at this time theyve adopted western style diets
37
Which 2 questions helped to determine that smoking is a cause of lung cancer?
The WHO and WHEN questions
38
Demonstrate how the WHO and WHEN questions helped to determine that smoking is a cause of lung cancer
MEN started smoking in the early 1900s - cancer started rising around 20 years later
WOMEN started smoking in the 40’s/50’s - lung cancer rates for women did not begin to rise until the 60s
39
The WHO could include which 2 factors?
Gender and age
40
Give an example of gender and age being an answer to the WHO question
Broken bones in YOUNG PEOPLE are more common in males - the result of accidents stemming from reckless behavior
Broken bones in the ELDERLY are more common in women - osteoporosis is more common in women
41
Epidemiologists study within human ______
Human populations
42
POPULATION refers to…..
People living within a specific area (population of the US, population of a school, population of a factory, etc)
43
Do epidemiologists use observational methods or experimental methods?
OBSERVATIONAL
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The biomedical sciences approach, in contrast, is a _____ method
Animal models of disease - experimental
45
Are there any uncertainties on the relevance of animal studies to humans?
Yes
46
Incidence rate is…..
The amount of cases over a specified period of time - related to tracking epidemics or SPIKES in cases
47
Prevalence rate is….
The total amount of cases that exist AT THAT MOMENT
48
How is death(mortality) rate involved in incidence rate and prevalence rate?
Comparing the amt of people that died of the disease being tracked
TO
The total population being analyzed
49
If death rate is HIGH, it is possible that incidence rate is ______ than prevalence rate
Higher
50
Explain why when the death rate is high the incidence is higher than the prevalence
Because most people have died of the disease during the specified time period
51
If death rate is low, the prevalence rate is _____ than the incidence rate
Higher
52
Explain why that when the death rate is low the prevalence is higher than the incidence
Because those people SURVIVE and are added to the people that already had the disease before the epidemic started
53
Explain when the death rate would be low
In the case of a chronic, non lethal disease
54
DISTRIBUTION is evaluating these rates based on _____,_____,and______
Different groups of people, different locations, and different times
55
DISTRIBUTION over DIFFERENT TIMES is simply….
Incidence rate (when)
56
DISTRIBUTION among DIFFERENT GROUPS is…
WHO
57
DISTRIBUTION among DIFFERENT LOCATIONS is ____
WHERE
58
What is a cohort?
A group/category of individuals for the purpose of looking at different outcomes of a study based on different variables
59
List 4 different examples of cohorts
1. Experimental cohort vs control cohort
2. Age related cohorts (toddler cohort, adolescent, adult, etc)
3. Dose related cohorts (high dose cohort, medium dose cohort, etc)
4. Gender related cohorts (male, female)
60
Answers to the WHO, WHEN, and WHERE questions provide clues to….
The causes of disease or the source of the outbreak
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“Answers to the who, when, and where questions provide clues to the causes of disease or source of the outbreak”
What kind of epidemiology is this?
Descriptive epidemiology
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The hypotheses generated by descriptive epidemiology are tested by…..
Formal epidemiologic studies that are designed to confirm or disprove a hypothesis
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Epidemiological studies are sometimes referred to as _____ or _____
Prospective or retrospective
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What is a prospective study?
Starts in the PRESENT and monitors groups of people in the FUTURE.
OR
They may start at a point in time in the past and look forward from their
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What are retrospective studies?
Looks into the PAST for causes of disease that people CURRENTLY SUFFER FROM
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In both retrospective and prospective studies, investigators are looking for…..
Associations between exposure to the suspected causative factor and the disease
67
Give an example of a prospective study
The Framingham Heart Study
68
When a group of people get sick over time during a prospective study, what questions will the investigators ask themselves about these sick people?
What may they have been exposed to?
Are there any similarities among the group that got sick?
69
Restrospective studies look at those who are ALREADY SICK. What 3 similarities might investigators look for?
-related
-common exposures
-work
70
Give an example of a GENERAL retrospective study
Mesothelioma patients - questioning reveals that they were all exposed to asbestos fibers
71
Intervention studies are conducted in very much the same way as….
Laboratory experiments on animals
72
Intervention studies are usually conducted to test which 2 things?
-treatment for a disease
-a preventative measure (such as a vaccine)
73
DRUG DEVELOPMENT is part of which core function of public health
??????
74
Give 3 reasons as to why only a limited number of possible interventions actually end up in clinical trials??
-Pre clinical trials show that they are not safe and effective
-ethical issues arise during development
-not cost effective
75
In testing treatments for SERIOUS diseases, what 2 things related to the intervention must exist for the testing to be ethical?
-there must be some doubt about the effectiveness of the intervention to JUSTIFY withholding it from some people (control group)
-there must be enough evidence that it will NOT HARM the people on whom it is tested (variable group)
76
The control group may be given a PLACEBO. What is a placebo?
An inactive substance similar in appearance to the drug or vaccine being tested
77
When a treatment for a disease is already known to exist, the trial may…..
Compare the new treatment with the existing treatment
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What is the purpose of the placebo?
To prevent subjects from knowing whether they are receiving the intervention
79
A placebo rules out…..
????
80
Many trials have found what interesting thing about placebos?
Up to a third of patients respond to a placebo as if it were an intervention (placebo effect)
81
In order for the tested intervention to be considered effective…..
It must have a higher response rate than the placebo
82
the most convincing clinical trials are conducted in a ————-manner?
Randomized, double blind manner
83
What does “randomized” mean?
Each subject is assigned to the control group or treatment group AT RANDOM
84
What does double blind mean???
Both the PATIENT and DOCTOR are blind as to whether the patient is receiving a drug or a placebo
85
Why should doctors also be blinded?
Studies have shown that patients respond more favorably to a treatment that the DOCTOR believes will work
ALSO
To prevent the possibility that doctors may interpret the patient’s conditions differently if they knew how the patient is being treated
86
In a THERAPEUTIC CLINICAL TRIAL…..
Both the experimental and control group are patients who have the disease for which a therapy is being tested
87
Therapeutic clinical trials are being conducted all the time by ———-
Pharmaceutical companies testing new drugs
88
What is the purpose of the FDA in relation to therapeutic clinical trials?
Requires that the safety and effectiveness of a new drug be demonstrated in a clinical trial before that drug can be approved for marketing
89
Give an example of a randomized double blind clinical trial of a preventative intervention
Polio vaccine (JONAS SALK) in 1954
90
The Salk vaccine reduced the ___ of polio
Incidence
91
Give another example of a randomized, controlled intervention (not polio)
The physicians health study
92
The physicians health study tested 2 hypotheses:
1. Does aspirin reduce mortality from heart disease?
2. Does beta-carotene reduce the risk of cancer
93
The physicians were divided into 4 groups:
1. Those who took aspirin and beta-carotene
2. Those who took aspirin and a placebo
3. Those who took beta-carotene and a placebo
4. Those who took 2 placebos
94
Why was the aspirin part of the trial halted midway through?
Because it was clear that the physicians taking aspirin were 50% less likely to have a heart attack than the groups taking the placebo
95
The beta-carotene part of the study found that……
There was no significant difference in the incidence of cancer between beta-carotene group and the placebo group
96
Give another example of an intervention study (not physicians health or polio)
Kingston-Newburgh study of fluoride for the prevention of tooth decay
97
Describe the Kingston-Newburgh study
Fluoride was added to the water supply of newburgh while Kingston’s was not.
10 years later, dental examinations were conducted on the school children in both cities
The children of newburgh had half as many decayed, missing, or filled teeth as Kingston
STRONGLY SUPPORTIVE OF THE VALUE OF FLUORIDATION IN PREVENTING TOOTH DECAY
98
Epidemiologists sometimes use cohort studies to link ___ to _____
Observations to possible exposures
99
The Framingham Heart Study, the Doll-Hill study, and the Hammond-Horn Smoking study are all….
Cohort studies
100
What is a well known cohort study that is still underway?
The Nurses Health Study
101
What did the Nurses Health Study find?
Nurses CURRENTLY taking oral contraceptives had a 50% higher risk of breast cancer, but the risk fell back to normal after they stopped taking them.
ALSO
Regular consumption of alcohol increases breast cancer risk by 10-40%
102
Epidemiologic studies are designed to not only determine an association between an exposure to a disease but also the _____ of that association
Strength
103
What is used to measure the strength of an association between an exposure and a disease?
RELATIVE RISK
104
A RELATIVE RISK OF 1.0 MEANS……
There is NO association between the exposure and the disease
105
A relative risk GREATER THAN 1 means….
There is an increased risk from exposure
106
A relative risk LESS THAN 1 means…
There is decreased risk from exposure
107
In the doll and hill study, the relative risk of smoking to lung cancer was…
23.7 - MAJOR EFFECT
108
In the nurses health study, the relative risk of breast cancer to contraceptive use was…
1.5
109
In the Physicians Health study, the relative risk of a heart attack in men taking aspirin is….
0.56 (less than 1) (not as convincing as smoking to lung cancer)
110
What is the difference between a COHORT STUDY and a CASE CONTROL study?
Cohort study - start by measuring exposure and then watching out for the development of the disease
Case control study - start with people who are ALREADY ILL and look back to determine their exposure
111
Why are CASE CONTROL STUDIES somewhat more efficient than cohort studies?
-they focus on a smaller number of people
-can be completed relatively quickly
112
In case control studies, _____ are compared to _____
Cases are compared to controls
Cases = people who have the disease
Controls = healthy individuals chosen to match the case as much as possible (age, sex, etc)
113
Small case control studies are commonly done to follow up on a hypothesis generated by ____ epidemiology. GIVE AN EXAMPLE
“Shoe leather” epidemiology
Example: lead poisoning in Michigan and L-tryptophan study
114
What was an important case control study in the mid 80s?
Sought the case of Reye’s syndrome- rare, deadly disease of children that occurred a few weeks after a child had recovered from a viral infection (such as chicken pox)
115
What was the hypothesis regarding Reye’s syndrome? What were the CASES and the CONTROLS associated with this case control study
That is was linked to the medications given to treat the viral illness
CASES = children who had been diagnosed with Reye’s syndrome and reported previous respiratory or gastrointestinal illness or chickenpox
CONTROLS = children who did not have Reye’s syndrome but who had been recently diagnosed with chicken pox, etc
116
Case control studies estimate the strength of the association between exposure and disease by calculating----
an ODDS RATIO
Ratio of exposed to nonexposed in case group/ ratio of exposed to nonexposed in the control group
estimate of the relative risk of a cohort study
117
the odds ratio for the risk of Reye's syndrome from salicylate was 42.7
What does this number mean?
children who are given aspirin to treat a viral infection are 42.7 times more likely to develop Reye's Syndrome than children who did not take aspirin
This is a VERY STRONG association
118
What did the FDA require as a result of the case control study of Reye's Syndrome?
warning labels on all aspirin bottles
119
What was another study that revealed similar results as the Nurses Health Study?
the British Breast Cancer Study
