Module 7 for Final (Ch. 8) Flashcards
A ____________ study is where 2 or more groups of people who do not have the investigated health outcome, but have different levels of exposure to an agent have their health outcome incidences compared.
A cohort study
what are some features of a cohort study?
- longitundinal study
- the cohort is followed over time until people have health outcomes
- cohort studies are the observational equivalent of an experimental study
- also known as an incidence study
what type of populations are studied in cohort studies?
- dynamic populations
- fixed populations
- closed populations
In a __________ population, people can come and go at any time.
dynamic population (also known as an open population)
In a ____________ population, members do not leave or enter at any time. This population/cohort is defined by an irrevocable event (like people impacted by a bomb).
fixed population
In a ____________ population, members do not leave or enter at any time, they are impacted by an irrevocable event, and they are followed up with for a brief period of time. An example of this type of population/cohort, would be people who ate contaminated food who are followed up with for 10 days.
closed population/cohort
In the air force cohort study on the effects of agent orange involving Vietnam veterans, who was the exposed group and who was the unexposed group?
Servicemen exposed to agent orange through the Vietnam War were the exposed. Servicemen on Vietnam War missions that did not involve agent orange.
In the air force cohort study on the effects of agent orange involving Vietnam veterans, what were the outcomes of interest?
Cancer, post-traumatic stress, adverse pregnancy outcomes
Match study population type to statement about incidence
- fixed cohort
- dynamic cohort
- closed cohort
- ________ studies and ________ studies use incidence rate to measure disease frequency.
- ________ studies use cumulative incidence to measure disease frequency
- fixed cohort
- dynamic cohort
- closed cohort
- fixed cohort studies and dynamic cohort studies use incidence rate to measure disease frequency.
- closed cohort studies use cumulative incidence to measure disease frequency
In a cohort study, exposed group is also known as the ________ and the unexposed group is known as the ________.
In a cohort study, exposed group is also known as the index group and the unexposed group is known as the referent or comparison group.
It can be difficult to classify the exposure status of people because exposures can change over time. True or False?
True. For example, a woman could be a heavy smoker or a non-smoker at different times in life.
What phrase refers to the risk of disease increasing as the insensity or duration of exposure increases?
Dose-response relationship
when possible investigators split up the exposed group by level of exposure (high, med, low), to assess the presence of a dose-response relationship.
During the follow up period, only one outcome is investigated and the length of the follow up period may vary. True or False?
False. During the follow up period, more than one outcome is usually investigated and the length of the follow up period may vary.
For a prospective cohort study:
Put the sequence of exposure, outcome, and study beginning in order
- outcome
- study begins
- exposure
In prospective cohort study:
1. exposure
2. study begins
3. outcomes occured
Put the sequence of exposure, outcome, and study beginning in order
- outcome
- study begins
- exposure
In retrospective cohort study:
1. exposure
2. outcome occured
3. study begins
In an ambidirectional cohort study:
Put the sequence of exposure, outcome, and study beginning in order
- outcome
- study begins
- exposure
In ambidirectiona cohort study:
1. exposure
2. outcome occured for certain time period
3. study begins and assesses past outcome occurrences
4. outcome is observed moving forward
Pros and cons of retrospective study
what are some pros of retrospective studies?
Retrospective cons: higher potential for bias, may not have good exposure data
Pros: cheaper, faster, good for disease with long latency
Pros and cons of prospective study
what are some pros of prospective studies?
Prospective cons: slower, more expensive, not good for long latency
Prospective pros: usually have good data, lower potential for bias
Prospective cons: slower, more expensive, not good for long latency
How are cohort study populations selected? True or False
* the participants in a cohort study are randomly selected
* Participants may self-select based on exposure
* Participants’ exposure may be a result of behavior
* Exposed and unexposed groups are exactly same except exposure
- False. The participants in a cohort study are not randomly selected, they are carefully selected by the investigators.
- True. Participants may self-select based on exposure.
- True. Participants’ exposure may be a result of behavior
- False. Exposed and unexposed groups are may differ in ways other than exposure level, and their difference may affect the study results.
Cohorts selected to study rare exposures are __________________
Cohorts selected to study rare exposures are special cohorts
Examples of rare exposures are medical procedures, natual disasters, rare occupational exposures
Cohorts to selected to study common exposures are ____________
Cohorts to selected to study common exposures are general cohorts
Common exposures like smoking and hypertension
Ideally, you want the unexposed
group to be as similar as possible to the
exposed group with respect to all other
factors except the exposure. True or False?
True
What is the conterfactual ideal?
The idea that ideally the unexposed group would be
as similar as possible to the exposed group except the exposure
In a cohort study, what are three possible sources of comparison group?
- internal comparison
- comparison cohort
- general population data
What is an comparison group that consists of unexposed members of same cohort?
An internal comparison
What is a comparison group made up of a cohort who is not exposed from another similar population?
A comparison cohort
What is a comparison group that is created using pre-existing data from the general
population as the basis for comparison?
General population data
What is the standardized mortality ratio?
The Standardized Mortality Ratio = Observed deaths/expected deaths
Differs from regular standardization because you an account for difference in age, race, gender. Interpret like a relative risk.
Why does healthy worker effect matter?
- Workers (even exposed ones) are typically healthier than the general population (which has healthy and ill people)
In a study with workers, you may not see an association between an occupational exposure and
an outcome
In a cohort study, what are good ways to get data on exposure?
- Pre-existing records
- Questionnaires, interviews
- Direct physical exams, tests, and environmental monitoring may be needed to ascertain certain exposures
- Biomarkers
In a cohort study, what are good ways to get data on outcome?
- Death certificates
- Physician, hospital, health plan records
- Questionnaires
- Medical exams
In any cohort study, the ascertainment of outcome data
involves tracing or following all subjects from exposure
into the future
If there are high losses to follow up, that may call into question what?
high losses to follow up could call the validity of the study into question
If there are losses to follow up in a cohort study, what are good ways of reaching out to participants?
- Phone or home visit
- Internet, National Change of Address System
- vital statistics registries, Social Security administration
- Contact relatives or friends
You analyze cohort study results by calculating of incidence of health outcome among exposed and unexposed groups. True or False?
True. Depending on available data, you can calculate cumulative incidence or incidence rates
To find the incidence rate in a cohort study, you should calculate the number of person-years. True or False?
True
see Module 7c powerpoint
Calculate the incidence of health outcome in this situation:
* A total of 47,036 woman-years of follow-up were
accumulated during which 56 breast cancer cases
occurred; 41 of those were in the exposed group
with 28,001 woman-years in that group
IR of exposed = 41/28,011 WY = 146.4 per 100,000 WY
IR of unexposed = 15/19,025 WY = 78.8 per 100,000 WY
RR = 146.4 per 100,000 WY/78.8 per 100,000 WY = 1.9
Meaning: Women who were treated with air collapse therapy and exposed to numerous fluoroscopic examinations had 1.9 times higher risk of developing breast cancer than women who were not exposed to these treatments
