About Risk

Disease risk is a way to describe how likely it is that a person will develop a particular disease. The chance that a person will develop a disease at some point during their lifetime is referred to as lifetime risk. Because the development of a disease can occur at different times in different people, risk is often calculated as an average among groups of people. The likelihood that a particular group of people will develop a disease compared to the average likelihood of developing the disease is called the relative risk.

Relative risk is calculated by comparing the risk in a group of people with certain characteristics against the risk of a control group (such as randomly selected individuals from the general population). For example, consider a group of people with high cholesterol, a known factor that increases the risk of developing heart disease. This group of people has a certain level of risk of developing heart disease that is higher than that of the general population - lets say a 1.5-fold higher chance. This means that 50% more people in the high cholesterol group will develop heart disease than will individuals in the general population.

As people in the two groups are monitored over time to determine whether they actually develop heart disease, we may find that 52% more people, not the 50% expected, in the high cholesterol group have developed heart disease. The difference between the actual occurrence of the disease and calculated disease risk is based on many factors, including the number of individuals in each group that are being compared. The more people in each group, the more accurate the risk estimate will be. It is important to remember that risk is a statistical term that best applies to large groups of people, and that your individual risk of developing a disease and the estimated risk based on a group of people may be quite different.

Genetic risk factors

Like cholesterol in the example above, genetic factors can also increase or decrease your risk of developing certain diseases. The level of risk associated with each of these genetic factors is estimated by comparing large groups of individuals who already have the disease with those who do not. The presence of the genetic factor is examined in each of these groups to determine whether it is present more or less often in the group who already has the disease.

Calculating risk estimates can get very complicated, particularly for diseases that involve multiple risk factors. For example, high cholesterol is not the only risk factor for heart disease; being overweight, having high blood pressure, and smoking also contribute to the risk of developing the disease. Furthermore, genetic and environmental factors can increase or decrease the overall risk, which is the reason why not all smokers or overweight people will develop heart disease or experience a heart attack.

How deCODEme assesses genetic risk factors

At deCODEme, we look at single points in the human DNA code, called SNPs, in different groups of people and determine whether the SNPs are associated with an increased risk of developing particular diseases. Using the deCODEme Genetic Scan, we can compare the risk of people with your SNPs and the other risk factors such as gender and ethnicity, to those of other groups for whom the risk of developing certain diseases has been calculated. Furthermore, in our risk calculations for diseases with multiple SNPs, we assume that the risk associated with the different loci behaves independently, i.e. the risk is multiplicative in nature. Although we believe this to be a good assumption, we emphasize that for most of the diseases this has not been confirmed in clinical studies.

However, it should be pointed out that many of the genetic risk factors for common diseases have not yet been discovered; the deCODEme risk therefore does not contain all of the genetic and environmental risk factors contributing to most diseases. These other factors can further increase or decrease an individual's risk.

The complexity of calculating risk estimates should always be kept in mind when you are reviewing your deCODEme risk analysis results. Though changes in lifestyle are recommended for everyone in order to reduce the risk of developing certain diseases, you should always consult with a healthcare professional before you make any medical decisions or take any actions based on your deCODEme risk analysis results.