8. Causality: Cause or Merely Association? Flashcards
What is a cause?
An exposure or factor that increases the probability of disease.
What is the purpose of working out the cause of a disease etc?
To use the knowledge gained to remove, avoid or protect against harmful factors.
What do cohort studies and case control studies investigate have in terms of proving a causal link?
Cohort studies study if there is an association between exposure and developing the outcome.
Case control studies study if there is an association between being a case and have had the exposure.
What are some possible explanations for systematic and random variation?
Confounding - known, possible or Unknown factors.
Bias - selection or information.
Chance - measured by p-value and confidence interval.
How can the strength of evidence for a cause-effect relationship be evaluated?
Using Bradford Hill’s viewpoints or criteria for inferring causality.
What are the association features evaluated in Bradford Hill’s viewpoint?
Strength, specificity and consistency of association.
What are the exposure/ outcome features evaluated in Bradford Hill’s viewpoint?
Temporal sequence, dose response and reversibility.
What are other evidence is evaluated in Bradford Hill’s viewpoint?
Coherence of theory, biological plausibility and analogy.
What does the Bradford Hill’s criteria suggest about the impact strength of association has on how likely a cause-effect relationship is?
A causal link is more likely with strong associations.
What does the Bradford Hill’s criteria suggest about the impact specificity of association has on how likely a cause-effect relationship is?
Causal link more likely when an outcome is associated only with a specific factor.
What does the Bradford Hill’s criteria suggest about the impact consistency of association has on how likely a cause-effect relationship is?
A causal link is more likely if the association is observed in different studies and different sub-groups.
What does the Bradford Hill’s criteria suggest about the impact temporal sequence has on how likely a cause-effect relationship is?
A causal link is more likely if exposure to the putative factor has been shown to precede the outcome.
What does the Bradford Hill’s criteria suggest about the impact dose response has on how likely a cause-effect relationship is?
A causal link is more likely if different levels of exposure to the putative factor leads to different risk of acquiring the outcome.
What does the Bradford Hill’s criteria suggest about the impact reversibility has on how likely a cause-effect relationship is?
A causal link is very likely if removal or prevention of the putative factor leads to reduced or non-existent risk of acquiring the outcome.
What does the Bradford Hill’s criteria suggest about the impact coherence of theory has on how likely a cause-effect relationship is?
A causal link is more likely if the observed association conforms with current knowledge.
What does the Bradford Hill’s criteria suggest about the impact biological plausibility has on how likely a cause-effect relationship is?
A causal link is more likely if a biologically plausible mechanism is likely or demonstrated.
What does the Bradford Hill’s criteria suggest about the impact analogy has on how likely a cause-effect relationship is?
A causal link is more likely if an analogy exists with other diseases.
What is epidemiology?
The study of the distribution and determinants of health related states or events in specified populations, and the application of this study to the control of health problems.
What two assumptions are made in epidemiology?
Disease does not occur at random, disease has causal and preventable factors that can be identified through systematic investigation.
What are the three requirements of Henle-Koch’s Postulates germ theory?
The agent must be necessary (in every case), specific (not found in other diseases) and sufficient (capable of reproducing the disease in experimental animals).
