Deck 14: From Association to Causation: Deriving Inferences From Epidemiologic Studies

Question 1

Which of the following statements is not evidence suggesting Exposure A as a causative agent on Disease X?

A) Exposure A is clearly linked to mediator M. Approximately 11% of mediator M patients will go on to have Disease X over a 10-year period.
B) Many of the observations regarding Exposure A and Disease X have been replicated repeatedly.
C) Prevalence of Exposure A in patients with Disease X is 90% to 100%.
D) Eradication of Exposure A heals Disease X at the same rate as other treatment of choice.
E) None of above

Answer 1

E
All of the answers suggest causal relationship between exposure and outcome."Exposure A is clearly linked to mediator M.Approximately 11% of mediator M patients will go on to have Disease X over a 10-year period" indicates the temporal relationship."Many of the observations regarding Exposure A and Disease X have been replicated repeatedly" indicates replication of the findings."Prevalence of Exposure A in patients with Disease X is 90% to 100%" means there is specificity of the association."Eradication of Exposure A heals Disease X at the same rate as other treatment of choice" is a cessation of exposure.All of the answers indicate that Exposure A is a causative agent for Disease X.

Question 2

Lack of physical activity is a known factor associated with colon cancer.However,colon cancer develops even among active individuals.Moreover,several individuals who perform very little levels of physical activity never develop colon cancer.Hence,in the causal relationship between physical inactivity and colon cancer,the lack of physical activity is

A) necessary and sufficient.
B) sufficient but not necessary.
C) necessary but not sufficient.
D) neither necessary not sufficient.
E) confounded.

Answer 2

D
Based on the previous information,physical inactivity is neither necessary nor sufficient to cause colon cancer.

Question 3

Human papillomavirus (HPV) infections are known to be a cause of cervical cancer.In most cases,HPV goes away on its own and does not cause any health problems.However,the worldwide HPV prevalence in cervical carcinomas is 99.7%.This indicates that HPV-negative carcinoma is extremely uncommon.In this case,HPV is which of the following?

A) A necessary and sufficient cause
B) A necessary but not sufficient cause
C) A sufficient but not necessary cause
D) Neither necessary nor sufficient
E) None of the above

Answer 3

B
Because most of all cervical cancer patients present HPV infection,this indicates that HPV is a necessary cause for cervical cancer.However,all HPV infection does not develop as cervical cancer,which means HPV is not sufficient to cause for cervical cancer.Therefore HPV is a necessary but not sufficient cause.

Question 4

Cardiorespiratory fitness,measured as VO₂ max in mL/kg/min (maximum oxygen consumption),is associated with increased longevity.Recent evidence suggests that higher fitness increases the life span.Those with a low VO₂ max have a life expectancy after 60 years of 7 years,those with moderate VO₂ max of 15 years,and those with a high VO₂ max have a life expectancy after 60 of 23 years.Which of the causal criteria is illustrated with this example?

A) Temporal relationship
B) Strength of association
C) Replicability of findings
D) Specificity of association
E) Dose-response effect

Question 5

Temporal relationship is a necessary criterion to establish causality.Which of the following epidemiologic study design allows to evaluate temporal relationship?

A) Cross-sectional
B) Case-control
C) Transversal
D) Cohort
E) Literature review

Question 6

In a hypothetical cross-sectional study,marriage was found to be strongly associated with increased levels of happiness.Authors concluded that marriage was a cause of happiness.However,a reviewer of this study argued that because it is a cross-sectional study,it could not be determined whether marriage caused happiness or happiness caused marriage.What criterion of causal relationships was not met in the study according to the reviewer?

A) Strength of association
B) Biologic plausibility
C) Dose response
D) Temporal relationship
E) Replication of findings