Question

In 1965, AB Hill described nine aspects of an association to consider before interpreting it as a causal association. The strength of association was listed first. please evaluate this aspect using Rothman's sufficient -component cause model.

Answer 1

In 1965, the English statistician Sir Austin Bradford Hill proposed a set of nine criteria to provide epidemiologic evidence of a causal relationship between a presumed cause and an observed effect. (For example, he demonstrated the connection between cigarette smoking and lung cancer.) The list of the criteria is as follows:

1. Strength (effect size): A small association does not mean that there is not a causal effect, though the larger the association, the more likely that it is causal.
2. Consistency (reproducibility): Consistent findings observed by different persons in different places with different samples strengthens the likelihood of an effect.
3. Specificity: Causation is likely if there is a very specific population at a specific site and disease with no other likely explanation. The more specific an association between a factor and an effect is, the bigger the probability of a causal relationship.
4. Temporality: The effect has to occur after the cause (and if there is an expected delay between the cause and expected effect, then the effect must occur after that delay).
5. Biological gradient (dose-response relationship): Greater exposure should generally lead to greater incidence of the effect. However, in some cases, the mere presence of the factor can trigger the effect. In other cases, an inverse proportion is observed: greater exposure leads to lower incidence.
6. Plausibility: A plausible mechanism between cause and effect is helpful (but Hill noted that knowledge of the mechanism is limited by current knowledge).
7. Coherence: Coherence between epidemiological and laboratory findings increases the likelihood of an effect. However, Hill noted that "... lack of such [laboratory] evidence cannot nullify the epidemiological effect on associations".
8. Experiment: "Occasionally it is possible to appeal to experimental evidence".
9. Analogy: The use of analogies or similarities between the observed association and any other associations.
10. Some authors consider, also, Reversibility: If the cause is deleted then the effect should disappear as well.

Researchers have applied Hill’s criteria for causality in examining the evidence in several areas of epidemiology, including connections between ultraviolet B radiation, vitamin D and cancer,vitamin D and pregnancy and neonatal outcomes, alcohol and cardiovascular disease outcomes,infections and risk of stroke, nutrition and biomarkers related to disease outcomes,and sugar-sweetened beverage consumption and the prevalence of obesity and obesity-related diseases. They have also been used in non-human epidemiological studies, such as on the effects of neonicotinoid pesticides on honey bees.Their use in quality improvement of health care services has been proposed, highlighting how quality improvement methods can be used to provide evidence for the criteria.

Rothman's minimal sufficient cause model can be systematically developed as a method for discussing and evaluating causation. The simplest model in terms of binary factors is developed here, including issues of parametrization, which lead to Sheps' measure of excess occurrence. Two examples show how the ideas apply in concrete cases. The notion of alternative realities is used to link population-specific equations to general causal constraints.