Lecture 7

Question 1

what are types of observational studies that seek to establish statistical association

Answer 1

• cohort studies

Question 2

does association mean causation

Answer 2

• no

Question 3

does statistical association imply clinical importance

Answer 3

• no

Question 4

which study measures exposure at the start of the study and then follows research participants over time to see who develops disease

Answer 4

• prospective cohort studies

Question 5

which study identifies cohorts based on measurements of exposure at some time in the past for some other purpose and then identifies which individuals developed or did not develop disease between the time of exposure and the start of the study

Answer 5

• retrospective cohort study

Question 6

cohort studies estimate the association between an exposure and a disease by comparing the ______ of disease in those who are exposed to those who are not

Answer 6

• incidence (risk)

Question 7

cohort studies have been used to study

Answer 7

• risk factors
• prognostic factors
• treatments

Question 8

the research design that argues most convincingly for causality is the

Answer 8

• randomized control trials

Question 9

the research design that argues most convincingly for causality is the

Answer 9

• RCT

Question 10

the findings that argue most convincingly are

Answer 10

• strong relationship

- dose response relationship

Question 11

what is a dose-response

Answer 11

• larger exposure associated with higher rates of disease

Question 12

what is temporality

Answer 12

• cause precedes effect

Question 13

what is strength

Answer 13

• large relative risk

Question 14

what is reversibility

Answer 14

• reduction in exposure followed by lower rates of disease

Question 15

what is consistency

Answer 15

• repeatedly observed in different situations

Question 16

what is biologic plausibility

Answer 16

• makes sense according to biologic knowledge of the time

Question 17

what is specificity

Answer 17

• one cause leads to one effect

Question 18

what is analogy

Answer 18

• cause and effect relationships already established for a similar exposure or disease

Question 19

what is the only criterion absolutely required to establish causality

Answer 19

• temporality

Question 20

temporality is ________ evidence, in itself, in favor of causality

Answer 20

• weak

Question 21

what is an observational study in which a group of people who do not have a condition but who could possibility develop it in the future is assembled

Answer 21

• cohort study

Question 22

information about the characteristics of people in the cohort is gathered when

Answer 22

• beginning and end of study

Question 23

advantage of retrospective study

Answer 23

• less costly and time consuming

Question 24

disadvantage of retrospective study

Answer 24

• past records may not be as accurate

Question 25

how to select participants for cohort studies

Answer 25

- select cohort from gen pop then measure exposure to factors of interest - select exposed and unexposed groups separately on the basis of their levels of exposure

Question 26

when a person in a cohort study develops the outcome of interest, what happens

Answer 26

- that person's time in the study is complete

Question 27

when a person considered to be censored in a cohort study

Answer 27

- develops outcome of interest - followed and don't develop outcome - lost to follow-up

Question 28

how to calculate hazard

Answer 28

number who develop outcome/total person time

Question 29

how to calculate hazard ratio

Answer 29

- exposed group/unexposed group

Question 30

what is meant by the hazard ratio being higher than the risk ratio

Answer 30

- participants in the exposed group develop the outcome prior to the end of the 5 year period.

Question 31

advantages of hazard ratios over risk ratio as outcome measures in cohort studies

Answer 31

- allow subjects to contribute different amounts to the denominator - represents odds of exposed group developing a disease EARLIER in time than unexposed group

Question 32

what does it mean if hazard ratio is greater than 1.0

Answer 32

- exposed group developing outcome more rapidly than unexposed group

Question 33

how to use cohort studies

Answer 33

- identify exposures that increase or decrease risk of disease - used to study natural history of a disease - investigate the effect of a treatment on a disease or condition

Question 34

what studies are used when patients are unlikely to participate in in a study because they or their doctors believe one of the treatments is not effective

Answer 34

- cohort studies

Question 35

criteria for critical appraisal of research studies

Answer 35

- research question and study design - sample - measures defined - statistical analysis - effect size (results) - internal validity - due to bias? - reasonable conclusion - relevance QSD MAE ICR SAME DI QCR (same di quicker)

Question 36

we use _______ to evaluate the strength of a study's evidence towards establishing a causal relationship

Answer 36

- reason and evidence

Question 37

the most widely used criteria to evaluate causality on the basis of epidemiological evidence are known as

Answer 37

- Bradford Hill criteria

Question 38

what is the evaluation of the validity, importance, and generalizability of original research articles called

Answer 38

- critical appraisal