Chapter 7: Study Designs: Cohort Studies

Question 1

Cohort

Answer 1

A group of individuals who share an exposure in common and who are followed over time; an example is an age cohort.

Question 2

Cohort effect

Answer 2

Consequence of long-term secular trends in exposure within a specific cohort.

Question 3

Cohort life table

Answer 3

A table that presents mortality statistics of all persons born during a particular year.

Question 4

Cohort study (also, prospective or longitudinal study)

Answer 4

A type of study that collects data and follows a group of subjects who have received a specific exposure. The incidence of a specific disease or other outcome of interest is tracked over time. The incidence in the exposed group is compared with the incidence in groups that are not exposed, have different levels of exposure, or have different types of exposures.

Question 5

Continuous variable

Answer 5

A type of variable that can have an infinite number of values within a specified range (e.g., blood pressure measurements).

Question 6

Disability-adjusted life years (DALY)

Answer 6

A measure that adds the time a person has a disability to the time lost to early death; thus, one DALY indicates one year of life lost to the combination of disability and early mortality.

Question 7

Life expectancy

Answer 7

Number of years that a person is expected to live, at any particular year.

Question 8

Nested case-control study

Answer 8

A type of research design wherein both cases and controls come from the population of a cohort study (see case-control study and cohort study).

Question 9

Periodic life table

Answer 9

A type of statistical table that provides an overview of the present mortality experience of a population and shows projections of future mortality experience.

Question 10

Population-based cohort study

Answer 10

A type of cohort study that includes either an entire population or a representative sample of the population (see Cohort study).

Question 11

Prospective cohort study

Answer 11

A type of cohort study design that collects data on exposure at the initiation (baseline) of a study and follows the population in order to observe the occurrence of health outcomes at some time in the future.

Question 12

Rate ratio

Answer 12

A more precise term when relative risk is calculated with incidence rates or incidence density.

Question 13

Relative risk

Answer 13

Ratio of the risk of disease or death among the exposed to the risk among the unexposed. The formula used is Relative risk = (Incidence rate in the exposed/Incidence rate in the nonexposed).

Question 14

Retrospective cohort study

Answer 14

Type of cohort study that uses historical data to determine exposure level at some time in the past; subsequently, follow-up mea-surements of occurrence(s) of disease between baseline and the present are taken.

Question 15

Temporality

Answer 15

Timing of information about cause and effect; whether the information about cause and effect was assembled at the same time point or whether information about the cause was garnered before or after the information about the effect.

Question 16

Years of potential life lost (YPLL)

Answer 16

A type of statistical measure that takes into account the effect of premature death caused by diseases; computed by subtracting the actual age of death of an individual from the average age of death in a population (arriving at the YPLL for the individual), and then summing the YPLL for each individual in the population (i.e., the United States) being studied for a specific cause of mortality.