Lesson 6 & 7: Case-Control Studies & Cohort Studies

What is the criteria for a factor to qualify as a confounder?

1) Must be independent risk factor for disease 2) Must be associated with exposure under study 3) Must NOT be intermediate step in causal pathway b/w exposure and disease

What are some limitations to retrospective cohort studies?

1) New data collection isn't possible, so we're restricted to only old stuff 2) Can't go back and recollect data 3) Confounders - may be other factors present that we would want to know about

What are the 5 advantages to case control studies?

1) can assess multiple exposures at same time 2) less time consuming 3) cheaper 4) good for examining rare diseases 5) safe

Confidence intervals provide information on: (2)

1) statistical significance 2) precision of the estimated measure of association

We get a bunch of people with a disease and compare them to a control group that doesn't have the disease of interest

Case control

Which study is more efficient for studying diseases that have a long latency period (i.e., a long time between exposure and manifestation of disease)?

Case control

Odds Ratio can be calculated in:

Case control studies

We start with a defined population. We separate the group into cases and controls. From there we see the individual groups and whether they were exposed or not exposed. This is what type of study?

Case control study

Type of study that describes characteristics of a group or cluster of individuals with the same disease or symptoms is known as:

Case series

Refers to a group of people that share some common characteristic, such as year of birth or graduation year.

Cohort

Relative risk can be calculated in:

Cohort

Study of a sample of individuals who have different levels of exposure that are hypothesized to be risk factors for the development of a disease

Cohort study

What is the second step in a cohort study?

Determine disease free/exposed and the disease free/unexposed

What are some things to rake into consideration when choosing among research strategies?

Ethics, Logical, disease related

What is the difference between group level matching and individual matching?

Group level = proportion of individuals with a given characteristic is the same across the case group & control group (ex/ all same gender or race) Individual level = every case is matched to a control (ex/ 50 yr old cancer woman matched w/ 50 yr old cancer-free woman)

What is the first step in a cohort study?

Identify all prevalent cases of the disease under study

Is case control suitable for rare exposures?

NO

For cross sectional study, can you calculate the disease rate?

NO - because there is no follow up

Can a confounder be on the pathway between exposure and disease?

No

Prevalence is defined as the number of existing ____ and ____ cases at a period or point in time divided by the _____.

Prevalence is defined as the number of existing new and old cases at a period or point in time divided by the total population.

We start with a defined population. Then we gather a disease-free sub-sample. We separate them via exposed and unexposed, and determine the disease state (has disease or does not have disease). This is what type of study?

Retrospective cohort

To assess whether the exposure and disease are related, what can be calculated in cohort studies?

Risk ratio

What are the disadvantages to selecting a hospital based sample of controls?

These people may differ from the general population of healthy people

to avoid selection bias, how should the controls be selected for in case control studies?

They should be selected from the same population that gave rise to the cases

TRUE OR FALSE: A disadvantage to case control studies is that selection of control can be problematic.

True

TRUE OR FALSE: Controlling for more than two potential confounders cannot be accomplished

True

TRUE OR FALSE: Data obtained can be used to determine the prevalence of a given disease or exposure in a cross sectional study

True

TRUE OR FALSE: In a cohort study, an investigatory recruits a group of disease free individuals, collects information at the baseline on their exposures and follows them over time to identify those who develop disease

True

TRUE OR FALSE: In a cross sectional study, the independent and dependent variables are assessed simultaneously.

True

TRUE OR FALSE: In a cross sectional study, the temporal relationship is often difficult to establish

True

TRUE OR FALSE: In recall bias, one group remembers past exposures differently than the other group

True

TRUE OR FALSE: In cross sectional, association can be examined using prevalence odds ratio

True

TRUE OR FALSE: Our goal in a cohort study is to start with a population at risk for the disease that we are interested in studying.

True

In cohort studies, what do we do to anyone who had the disease of interest?

We exclude them If it was a cohort study, we want to exclude anyone who already had the disease of interest (critical distinction b/w cohort and case control)

Is case control good for rare diseases?

Yes

For cross sectional study, can you calculate odds ratio?

Yes - this is close approximation of risk ratio

selection of subjects based on disease

case control

Selects subjects based on disease/outcome

case-control

Selection of subjects based on exposure

cohort

When a disease is present at its usual level of incidence in a city, this is known as a:

endemic

What are the two types of studies?

experimental and observational

for follow up studies, selection of subjects is based on:

exposure status

What is a problem for both case control and cohort studies, but a more significant problem for case control studies?

patient recall of exposure

Mortality rate is a:

prevalence rate

In case control studies, a major problem is:

recall bias

One limitation to case control is that it is limited to examining a:

single outcome