Epi Inference Flashcards
Describe disease causation.
It is usually multi-factorial, and a multi-step sequence that may or may not result in clinical disease.
What is the epidemiologic triad?
What is the epidemiologic definition of a “cause”
“A factor is considered a cause of a disease if it is part of a complex of ciorcumstances in which the relative frequency of disease is increased by its presence and reduced by its absence.”
What is a “risk factor”
An attribute associated with the occurrence of health-related condition.
Like: aspect of personal behavior or lifestyle, environmental exposure, inborn or inherited characteristics, not necessarily casual
Several nuanced synonyms: predisposing factor, risk marker, precursor, determinant
What is a “Necessary cause”
a cause that must always precede an effect
What is a “sufficient cause”
A cause that always produces an effect
What are “Necessary Conditions”
“X is a necessary condition for Y” = If we don’t have X, then we won’t have Y OR Without X, you won’t have Y
To say that is a necessary condition for Y does not mean that X guarantees Y.
What are “Sufficient Conditions”
The exposure is enough to cause the outcome to develop
The exposure guarantees the outcome will develop, so 0 would be in the no disease exposed group
“X is a sufficient condition for Y” = if we have X, we know that Y must follow OR X guarantees Y
When is a cause necessary and sufficient?
To develop disease, one must have the cause. The cause guarantees the disease
Ex: HIV and AIDS in the past
When is a cause necessary and not sufficient?
To develop disease, one must have the cause. The cause does not guarantee the disease.
Ex: HPV and cervical cancer
When is a cause not necessary but sufficient?
Disease can occur without the cause. The cause guarantees the disease
Ex: High-dose exposure to pesticides or ionizing radiation and sterility in men
When is a cause neither necessary not sufficient?
Disease can occur without the cause. The cause does not guarantee the disease.
Ex: sedentary lifestyle and coronary heart disease
What are the epidemiologic guidelines for establishing a cause-effect relationship?
temporal sewuence
strength of association
dose response relationship/biologic gradient
consistency of the association/replication
coherence (biologic plausibility)
specificity of the association
experiment (cessation of exposure)
analogy
consideration of alternate explanations
What is temporal sequence?
Describe strength of the association.
What is dose-response relationship?
Does risk for disease increase with the degree of exposure?
What is consistency of the association?
What is coherence of the association? (biologic plausibility)
What is the specificity of the association?
What is analogy?
What is bias?
Systematic error in the design, conduct, or analysis of a study that results in a mistaken or distorted estimate of an exposure’s effect on the outcome.
Note: Perfect statistical analysis of the data cannot correct for systematic error in the design and conduct of the study
What are the two principal types of bias?
1) selection bias
2) information bias
What is selection bias?
Error due to systematic differences in characteristics (e.g. past exposures) between those who take part in a study and those who did not
The problem: the association between exposure and outcome may differ between those who participate in the study and those who do not participate
What are the consequences of selection bias?
The measure of association is distorted due to procedures used to select subjects and from factors that influence study participation. Usually inferred, rather than observed. Try comparing by known characteristics.
