Chapter 7: Study Designs: Cohort Studies

Question 1

What is a cohort study?

Answer 1

a type of panel study where individuals in the panel share a common characteristic

Question 2

What is temporality?

Answer 2

time order. refers to the timing of a cause (exposure) and effect (health outcome)

Question 3

Cohort?

Answer 3

a pop., group, or subset thereof that is followed over a period of time. They are distinguished by a certain characteristic

• comes from the Latin word cohors, one of the 10 divisions of an ancient Roman military legion
• Ex: a school group or at work

Question 4

What is a cohort effect?

Answer 4

the influence of membership in a particular cohort

Question 5

Cohort analysis?

Answer 5

the tabulation and analysis of morbidity/mortality rates in relation to the ages of a specific group of people(cohort) identified at a particular period of time and followed as they pass through different ages of their life span
-popularized by Wade Hampton Frost

Question 6

Life expectancy?

Answer 6

the # of years that a person is expected to live, at any particular year

Question 7

years of potential life lost (YPLL)

Answer 7

takes into account the effect of premature death caused by weighting deaths that happen at younger ages
-Ex: an average person is expected to live until 65 but they die at 60, so the YPLL would be 5 years lost

Question 8

disability-adjusted life years (DALY)

Answer 8

adds the time a person has a disability to the time lost to early death

• DALY=YLL+YLD
• Ex: a person born w/ autism has a life expectancy of 60 years. They live and die at age 27. Would that add 27 to 60 years?*

Question 9

MPM?

Answer 9

malignant pleural mesothelioma

Question 10

measures of effect?

Answer 10

a quantity that measures the effect of a factor on the frequency or risk of a health outcome or effect

Question 11

Varieties of cohort studies?

Answer 11

-pop. based
Ex: Framingham study
-exposure based
Ex: Use of special exposure groups such as members of prepaid medical care plans

Question 12

What is a continuous variable?

Answer 12

a type of variable that has an infinite set of possible values w/in a specified range
-Ex: blood pressure measurements

Question 13

What is a discrete variable?

Answer 13

a variable that has distinct values for each measurement

Question 14

What is the directionality of exposures in cohort design?

Answer 14

• prospective (present to future)
• retrospective (past to present)
• historical prospective (past to present to future)

Question 15

prospective cohort study?

Answer 15

determine levels at baseline (present) and follow up for occurrence of disease sometime in the future.
-enable investigator to collect data on exposures

Question 16

retrospective study?

Answer 16

tests “etiological hypotheses in which inferences about exposure to the putative casual factor(s) are derived from data relating to characteristics or events or experiences of the person in the study

Question 17

retrospective cohort study?

Answer 17

makes use of historical data to determine exposure level at some baseline in the past; follow up from baseline of past to occurrences in the present

Question 18

historical prospective cohort study

Answer 18

also called an ambispective cohort study. it’s a design that makes use of both retrospective (to determine baseline exposure) and prospective (to determine disease incidence in the future) features

Question 19

Active follow up?

Answer 19

denotes the situation where the investigator must obtain data on subsequent incidence of the outcome. Must be in direct contact w/ the cohort
-Ex: disease, change in risk factor, change in biological marker, etc.)

Question 20

Passive follow up?

Answer 20

doesn’t require direct contact w/ the cohort members. Possible when databases containing the outcomes of interest are collected by organizations outside of the investigative team

Question 21

relative risk?

Answer 21

the ratio of risk of disease or death among the exposed to the risk among the unexposed. Called a measure of effect

• Expressed as (cumulative incidence as exposed/ cumulative incidence as unexposed)
• RR=(A/(A+B))/(C/(C+D))

Question 22

nested case control study?

Answer 22

a type of case control. cases and controls are drawn from the pop. in a fully enumerated cohort

Question 23

case cohort study?

Answer 23

an alternative. involves random selection of controls from the study cohort instead of using matching. These controls would not be matched to the cases and would be selected after a time period has elapsed

Question 24

Life Table Methods?

Answer 24

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Question 25

Survival Curves?

Answer 25

a method for portraying survival times

Question 26

What is blinding?

Answer 26

masking individuals or their issues in a study. To prevent bias of the investigator

Question 27

Which of the following is a characteristic of a cohort study?

Answer 27

Exposed and nonexposed individuals compared with respect to incidents of outcomes

Question 28

Which of the following is a characteristic of a case-control study?

Answer 28

Diseased and no diseased individuals compared with respect to prior exposures

Question 29

Assuming that the sample population is representative of the study population, and you would like to apply the findings of this study to all people in the UK (from where the participants were selected), what would need to be assured?

Answer 29

• External validity

- Generalizability