What are absolute and relative risks?
Absolute risk of a disease is your risk of developing the disease over a time-period. We all have absolute risks of developing various diseases such as heart disease, cancer, stroke, etc. The same absolute risk can be expressed in different ways. For example, say you have a 1 in 10 risk of developing a certain disease in your life. This can also be said a 10% risk, or a 0.1 risk - depending if you use percentages or decimals.
Relative risk is used to compare the risk in two different groups of people. For example, the groups could be 'smokers' and 'non-smokers'. All sorts of groups are compared to others in medical research to see if belonging to a group increases or decreases your risk of developing certain diseases. For example, research has shown that smokers have a higher risk of developing heart disease compared to (relative to) non-smokers.
A couple of examples may illustrate this better.
An example when talking about risks of disease
Say the absolute risk of developing a disease is 4 in 100 in non-smokers. Say the relative risk of the disease is increased by 50% in smokers. The 50% relates to the '4' - so the absolute increase in the risk is 50% of 4, which is 2. So, the absolute risk of smokers developing this disease is 6 in 100.
An example when talking about treatments
Say men have a 2 in 20 risk of developing a certain disease by the time they reach the age of 60. Then, say research shows that a new treatment reduces the relative risk of getting this disease by 50%. The 50% is the relative risk reduction, and is referring to the effect on the '2'. 50% of 2 is 1. So this means that the absolute risk is reduced from from 2 in 20, to 1 in 20.
No comments:
Post a Comment