Biologic gradient refers to the presence of a mono- tone (unidirectional) dose–response curve. We often expect such a monotonic relation to exist. For exam- ple, more smoking means more carcinogen exposure and more tissue damage, hence more carcinogenesis.

What are Hill’s criteria for causality?

Sir Austin Bradford Hill proposed criteria to establish such an argument. These criteria include the strength of the association, consistency, specificity, temporal sequence, biological gradient, biologic rationale, coherence, experimental evidence, and analogous evidence.

What is a biological gradient?

Biological gradient – Changes in the intensity of the exposure results in a change in the severity or risk of the outcome (i.e. a dose-response relationship).

What are the criteria for causal inference?

Hill’s Criteria for Causality

• Strength of the association.
• Consistency.
• Specificity.
• Temporality.
• Biological gradient.
• Plausibility/Coherence.
• Experiment.
• Analogy.

What are the guidelines for judging whether an association is causal?

The most important of these guidelines are ‘ strength’ (a strong association is more likely to be causal than a weak one), ‘consistency’ (an association is observed in different studies, under different circumstances, times and places), ‘biological gradient’ (i.e. dose-response – the effect should tend to be greater

What is Hill’s criteria in epidemiology?

The Bradford Hill criteria, otherwise known as Hill’s criteria for causation, are a group of nine principles that can be useful in establishing epidemiologic evidence of a causal relationship between a presumed cause and an observed effect and have been widely used in public health research.

What are the four requirements for causality in experiments?

Establishing Causality

• Temporal sequencing — X must come before Y.
• Non-spurious relationship — The relationship between X and Y cannot occur by chance alone.
• Eliminate alternate causes — There are no other intervening or unaccounted for variable that is responsible for the relationship between X and Y.
• Temporal Sequencing.

What is causality in epidemiology?

Epidemiology has a vested interest in causation as, despite its numerous and often vague definitions, it is a discipline with the goal of identifying causes of disease (both modifiable and nonmodifiable) so that the disease or its consequences might be prevented.

Is association the same as causality?

Association is a statistical relationship between two variables. Two variables may be associated without a causal relationship. Causation: Causation means that the exposure produces the effect.

What is the weakest Bradford Hill criteria?

Results from these studies must demonstrate an Odds Ratio (OR) or Relative Risk (RR) of at least 2.0 or above in order to be meaningful. Anything between 1 and 2 is weak, while >2 is moderate and >4 is considered strong.

What are the four types of causal relationships in epidemiology?

 If a relationship is causal, four types of causal relationships are possible: (1) necessary and sufficient; (2) necessary, but not sufficient; (3) sufficient, but not necessary; and (4) neither sufficient nor necessary.

What is causal association mean?

— Association between two variables where a change in one makes a change in the other one happen.

When is an association causal?

Association should not be confused with causality; if X causes Y, then the two are associated (dependent). However, associations can arise between variables in the presence (i.e., X causes Y) and absence (i.e., they have a common cause) of a causal relationship, as we’ve seen in the context of Bayesian networks¹.