Attributable risk

The attributable risk is that risk which is due to the exposure to a risk factor in clinical and epidemiological studies. In contrast, the relative risk of the risk of disease by comparing exposed and non- exposed individuals.

The attributable risk indicates the percentage by which you can reduce disease incidence, it would eliminate the risk factor. For example, in smokers, the risk of suffering from lung cancer, higher than in non-smokers - but also occur in non-smokers, but just rare cases of lung cancer on.

In contrast to the relative risk, the attributable risk takes into account the rarity or the incidence of disease. As an illustration, a hypothetical example - two behaviors between which a person might choose:

• A behavior doubles the risk of lung cancer, halved the oral cavity cancer risk.
• Behavior B halved the risk of lung cancer, and makes oral cancer twice as often.

A poorly informed person would select the random behavior or even agree with the behavior of A, because the relative risk for both disorders is the same - namely the doubling or halving of a morbidity risk. Oral cavity cancer occurs but much less frequently ( about 10,000 diseases / year in Germany; lung cancer: 50,000 ). The likelihood of suffering one of the two diseases is in practice B is less (ie, oral cavity cancer: 20,000 cases, 25,000 lung cancer, a total of 45,000 cases per year).

The attributable risk of a population corresponds to the attribute variables risk multiplied by the population.

Risk of persons who were exposed to the risk factor:

Risk of persons who were not exposed to the risk factor:

The attributable risk then is the difference:

An example with fictitious data

Suppose you want to investigate the association between the occurrence of heart attacks and smoking. We observed 10,000 patients and determines whether they smoke or not and whether they have ever had a heart attack. It results in the following crosstab:

It is as follows attributable risk

That is, the risk of suffering a heart attack, to be increased by 5.625 % points (ie, from 6.5% to below 0.9 %) reduced if you stop smoking.