Cohort studies - quiz

Question 1

What are the two things that cause and effect under cohort studies are necessary ?

Answer 1

1) Temporality

2) two time points

Question 2

what are the pros of a cohort study?

Answer 2

1) Provides direct estimate of risk
2) useful for rare exposures
3) can study more than one outcome
4) temporal relationships are more clear

Question 3

what is the formula for number of non- exposed subjects?

Answer 3

C+D

Question 4

What are the two things that cohort studies are based on ?

Answer 4

1) they are population based

2) they are exposure based

Question 5

what is the difference between a cohort study in a retrospective point vs a case-control study in a retrospective point?

Answer 5

Cohort study uses entire cohort study of exposed people , while case control uses cases and controls who do not represent entire cohort of exposed.

Question 6

what is a cohort study ?

Answer 6

a study of population group or subset that is followed over a period of time

Question 7

what are the disadvantages of a cohort study?

Answer 7

1) Larger, longer, more expenses
2) prone to bias like attrition, and misclassification
3) not useful for rare diseases.

Question 8

what is the healthy worker effect bias mean ?

Answer 8

people with severe illnesses excluded from employment, but not from the general population. As a result, comparisons of mortality rates btw an employed group and the general population will be biased.

Question 9

What is the most important characteristic of cohort studies?

Answer 9

Almost always a primary data collection, and is always identified based on exposure status.

Question 10

what is a population based cohort study mean ?

Answer 10

entire population or representative sample

Question 11

what is the incidence of disease in non-exposed group?

Answer 11

C/(C+D)

Question 12

what happens in a prospective study?

Answer 12

two groups, exposed and non exposed are followed up over time to see who has the outcome and who does not.

Question 13

What are some things to keep in consideration for cohort?

Answer 13

1) availability of exposure data
2) size and cost
3) data collection and data management
4) follow-up issues
5) follow-up issues
6) sufficiency of scientific justification

Question 14

what does exposure based cohort study mean ?

Answer 14

based on exposure of interest, and comparison groups

Question 15

What kinds of bias can occur in a cohort study?

Answer 15

Selection bias, confounding, and even misclassification

Question 16

what are some cohort study characteristics ?

Answer 16

1) use individual data
2) Identified Based On Exposure Status
3) Can be retrospective or prospective
4) Able to evaluate multiple outcomes
5) give information on incidence
6) almost always a primary data collection

Question 17

what is the formula for Relative risk in words?

Answer 17

incidence rate in exposed / incidence rate in non-exposed

Question 18

what is the measure of association for cohort studies?

Answer 18

relative risk (RR)

Question 19

what is the name of cohort studies used? Define them:

Answer 19

Prospective/ longitudinal study

Definiton ^ : starts with group of people without outcome that we are interested in studying, but they are at risk of it.

Question 20

What do cohort studies try to understand ?

Answer 20

the cause and the effect

Question 21

what happens in the retrospective cohort study?

How do we measure it ?

Answer 21

this is the one where we use historical data to find the exposure level at baseline in the past.

We follow-up for Disease between baseline and the present.

Question 22

what is the incidence of disease in exposed group?

Answer 22

A/ (A+B)

Question 23

What is the relative risk formula in terms of a 2x2 contingency table?

Answer 23

[ a/(a+b) ] / [ c/(c+d) ]

Question 24

what is the formula for number of exposed subjects ?

Answer 24

A+B

Question 25

what is the cohort effect?

Answer 25

the influence of a membership in a particular group: this changes exposure/ outcomes due to membership on group

NOTE: membership means same as relationship in group. Friendship in group. etc.

Question 26

What are some other measure of association to consider for a cohort study?

Answer 26

Rate ratio
Attributable risk
Population-Attributable Risk

Question 27

What does the term attrition under selection bias in a cohort study mean ?

Answer 27

Loss-to-follow up, especially problematic of differential