# Understanding Absolute vs Relative Risk and Why It’s Important for Your Health

Every day, media headlines grab attention with percentages about risks that threaten overall health or behaviors that contribute to disease. Although reports state these risks as probabilities, it is easy to misinterpret these numbers. Evaluating risk is a method medical professionals use to more accurately determine the probability of contracting a disease or illness. it can also indicate the likelihood of a positive outcome for a specific treatment. Absolute risk and relative risk are different evaluations.

## Why Understanding Risk is Important

Some diseases and illnesses are more likely to respond to specific treatments and behavioral changes. Some treatments are highly effective and others that are more experimental or less-developed. Evaluating risk allows both health professionals and patients to determine the best course of treatment. Relative risk and absolute risk are both measured in percentages, but they differ in important ways. Doctors measure relative risk by comparing two groups, an affected group, and a control group, but the measurements can be misleading. Absolute risks reflect the probability of a specific outcome by measuring only the affected group.

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## Media Interpretation of Risk

A news story may report that those who eat processed foods are 30 times more likely to develop cancer. This is an example of generalized information — a relative risk. The number does not accurately reveal the odds of contracting cancer by eating processed foods because the data leaves out too many variables. In comparison, a headline stating 12 out of 100 women will develop breast cancer at some point in their lives is an example of absolute risk. This is a fact, backed by research, with specific, documented parameters.

## Relative Risk Specifics

Relative risk is often expressed as increased or decreased percentages. An example of relative risk is to say a medication lowers the risk of stroke in patients by 30 percent. The study on which that number is based is comparing a group who took the medication, with a group who did not. If 100 people were studied, with 50 receiving the drug and 50 not, then the 30 percent that benefited represented only 15 people (30 percent of 50, not 30 percent of 100). Although semantically correct, the relative risk can be misleading when it comes to the effectiveness of the drug.

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## Absolute Risk Specifics

Although higher absolute risk indicates an increased probability that an event will happen, it does not mean that it will happen. Absolute risk can reveal the odds of an outcome over a specific period. If an individual stops a behavior that increases risk, his or her absolute risk for a specific disease will likely decline over time. For example, an individual with a genetic history of liver issues who stops consuming alcohol reduces his or her chance of contracting a liver disease.

## Absolute Risk Reduction (ARR)

At some point in the medical treatment process, a doctor and patient will usually consult about the risks associated with a specific treatment. Risk evaluation helps determine the outcome between control and treatment groups. Absolute risk reduction is the total reduction in risks provided by a specific treatment. If the ARR is eight percent in a treatment group of 100 people, that means eight of them avoided a bad outcome. In some cases, however, ARR reflects mortality.

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## Relative Risk Reduction (RRR)

Determining risk is about probabilities. Relative risk reduction indicates how much a specific treatment lowered the risk of bad outcomes when compared to its control group — those who did not receive the treatment. The greater the risk, the more likely medical intervention will be successful. RRR can effectively determine treatment plans. It provides information into not only the effectiveness of a treatment but also the risks of not providing treatment. In some cases, it is a more effective determinant than absolute risk reduction.

## Number Needed to Treat (NNT)

The NNT is an estimated number that represents how many people must be treated to make an impact on one single individual or prevent one bad outcome. It only uses ARR. Treatment will not help 100 percent of those who receive it. Some treatments may cause negative effects, while others may have no effect at all. Basically, the NNT explains how many people need to be treated through drugs, surgery, or procedures for one of them to benefit. It is an effective method of determining whether or not a person will benefit from a treatment or medication.

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## Personal Perception of Risk

Discussing the pros and cons of specific treatments or the prognosis of a disease is important. A physician should be able to answer questions as to the NNT and the absolute risks based on findings from research. However, different people are willing to accept different levels of risk. Feeling a lack of control or fear of a difficult outcome may be stronger influences than percentages when making decisions about treatment.

## Distinguishing Between Absolute and Relative Risk

According to a study by the Harding Center for Risk Literacy, medical journals and scientific publications are failing to provide absolute risk numbers when documenting research results. Instead, they use relative risk numbers, which offer misleading information. These relative numbers are plucked from research publications and make their way into pamphlets and news stories. Because of this, health consumers should learn to ask physicians for absolute risk percentages as well. This will make them more aware of the risks involved with treatments or their likelihood of contracting a disease.

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## Understanding Risk and How it Affects Individual Health

An essential element of quality medical care is understanding effective methods of treatment and any risks associated with the treatments or behaviors. Determining whether the possible complications or side effects of a specific treatment are worth the potential risks is key to having control over one’s care. When an individual is speaking with a doctor about the probable success of a particular treatment, asking about NNT can help determine whether the treatment is worth it.

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