Absolute risk and relative risk

The risk of any health condition can be described in two ways: absolute risk and relative risk.

Absolute risk describes the chance of developing a health condition during a given period of time. For example, the absolute risk of a woman developing uterine cancer (including endometrial cancer) by the age of 85 years in Australia is 1 in 40. 

Most scientific and medical reports use relative risk. Relative risk describes the risk of developing a health condition in one group of people compared with another group of people. It does not tell you what the total risk is, but it does tell you how much the risk might change in response to a situation.

For example, the relative risk of endometrial cancer is higher in women who are overweight or obese compared with women who are a healthy weight. For every 5kg increase in weight, the risk of endometrial cancer increases by 16%. The absolute risk of developing endometrial cancer is still relatively small in women who are overweight but the risk is higher than in women who are healthy weight.

Relative risk can be expressed in several different ways. In the following example, all of the expressions have the same meaning:

• The relative risk is 1.5.
• The risk is 1.5 times higher.
• There is a 50% greater risk.

Similarly, if the relative risk is 9.0, this means that the risk is 9 times higher in people exposed to the risk factor than in people not exposed to the risk factor.

In the case of most risk factors for human diseases, an increase in risk depends on intensity, frequency and duration of exposure, as well as other contextual factors.

Risk factors

A risk factor is something that is associated with an increased chance of developing a health condition such as endometrial cancer. Risk factors for endometrial cancer include lifestyle factors (such as being overweight or obese), reproductive factors (such as being younger when periods start), factors related to medical history and use of medications, and factors related to family history and genetics.

Having one or more risk factors does not mean that you will develop endometrial cancer. Many women have at least one risk factor but will never develop endometrial cancer. Some women who develop endometrial cancer have no known risk factors.

Even if a woman with endometrial cancer has a risk factor, it is hard to know how much that risk factor contributed to the development of her disease.

Protective factors

A protective factor is something that is associated with a decreased chance of developing a health condition such as endometrial cancer.

Protective factors for endometrial cancer include lifestyle factors (such as physical activity), reproductive factors (such as having children and breastfeeding) and factors related to medical history and use of medications.

Modifiable risk factors

A modifiable risk factor is something that a woman can change to reduce her risk of developing endometrial cancer. This includes keeping to a healthy body weight, breastfeeding and regular physical activity.

It is estimated that 1 in 3 endometrial cancers diagnosed each year are attributable to modifiable factors. 

Unproven or unlikely factors

The evidence about risk factors and protective factors comes from research studies. If similar results are seen in several studies involving large numbers of people, we can be confident in the findings. This includes studies that show no association between a particular factor and the risk of the health condition.

However, the evidence is not always entirely clear. This may be because studies are too small or because of how the studies were run. In this case, the evidence is said to be unproven or inconclusive.

What does this mean for you?

Over the course of your lifetime there are many things that can affect your risk of endometrial cancer. Information about risk can help you make choices about lifestyle and other modifiable factors that affect risk for endometrial cancer.

This website describes what we know about factors associated with an increased or decreased risk of endometrial cancer and what you can do to reduce your risk of endometrial cancer.