Key points:

• • Risk means the chance that something bad will happen.
  • Benefit is the possibility that something good will happen.
  • You might have to decide whether the possible benefit of a treatment or procedure is more important to you than the possible risk.
  • Deciding what risk you are comfortable with is personal. Everyone has different ideas about what is okay for them, or their family.
  • There are questions you can ask your doctor to help you decide.

Understanding Risk and Benefit

“Understanding health risks is key to making your own health care decisions. It gives you perspective on potential harms and benefits, so you can make smart choices based on facts and not fears.”[i]

When people talk about risk in health care, they are usually talking about the chance of a negative outcome (something bad) happening.  This can be:

• • • an unpleasant or dangerous side effect of medication or treatment – such as a rash, headache or upset stomach
    • your health getting worse – for example the treatment not working, or making you sicker
    • getting a new health problem – like high blood pressure or diabetes
    • a life-threatening incident – such as an interaction between two medicines that could kill you.

In health care, people also talk about the chance of a benefit (a good outcome) happening, for example getting better or living longer.

You may have to decide:

Is the chance of that something bad will happen more likely, or more important to you, than the possibility that something good will happen?

For example, you might have to decide:

Is taking medicine every day to reduce the chance that you could have a stroke or heart attack in the future, worth the possible side effects of taking the medication?

Information to help you decide about risks and benefits

When making decisions about risks and benefits you need information about:

• • • How likely is it that something bad will happen to someone like you (your age, gender, with your medical conditions and ethnic background)?
    • How bad that thing is and how much of an impact will it have on you? Everyone has different ideas about what is okay for them or their family.
    • How likely is it that something good will happen to someone like you?

You can ask your doctor or other health professionals to talk to you, or give you information, to help you understand the answers to these questions.

This information can help you decide what is more important to you – the possible risk or risks, or the possible benefit.  You might be willing to take a chance that the bad thing will happen if it means you might get the possible benefit. For example, you might decide that it is okay to risk feeling tired from a new medication if it means that you have a better chance of the possible benefit happening – lower risk of a stroke in the future.

Your health provider can tell you about the possible outcomes (both good and bad), but they can’t give you definite and guaranteed outcomes. For example, your doctor can tell you that taking a medication means that you are less likely to have a stroke, not that it means you definitely won’t have a stroke.

Describing risk

Sometimes people use words to describe risk, and sometime they use numbers.

“Rare” and “common” are examples of words that describe risk. If your doctor uses words, make sure you understand what they mean.  What a doctor means by “rare” or “common” may not be the same as what you think the term means.

There are different ways to use numbers to describe risk. Doctors may use a percentage to explain how common or uncommon an outcome is. A percentage means “out of 100” – a risk that affects 5% of patients, means 5 in every 100 people.

Sometimes, an outcome can affect fewer than 1 person in 100. You might find it easier to understand if your doctor talks about 1,000 people instead of using a percentage. It is easier to image 3 people out of 1,000 than 0.3 of a person.

You can ask your doctor to tell you how many people out of 1,000 would have a negative outcome. Some people find it useful to imagine 1,000 people as all the people in your suburb, and 100 people as all the people in your street.

Ask your doctor to describe the risk in a way that works for you. 

Absolute vs Relative Risk

To understand the potential risks or benefits of a medical treatment or behaviour change, it helps to focus on “absolute risk”.

Absolute risk is the chance of something happening, for example a health problem.

Relative risk compares the absolute risk for one group of people to the absolute risk for another group of people.

Here is an example of the difference between absolute risk and relative risk.

Absolute Risk Reduction: If you have this test every two years it will reduce your chance of dying from this cancer in the next 10 years from around 3 in 1000 to around 2 in 1000.

Relative Risk Reduction: If you have this test every 2 years, it will reduce your chance of dying from this cancer by around one-third (or 30%) over the next 10 years.  This compares the risk of the people who have the test with the risk of the people who don’t have the test.

Which gives you a clearer understanding of the impact of the test on your risk of dying of cancer? The first number tells you what your actual risk is now (3 in 1000), and how it will change if you do the test (2 in 1000).  The other number is also accurate, but it doesn’t help you understand what your risk actually is, or help you to decide if having the test every two years is worth it.

Talking about absolute risk helps you understand the risks and benefits that apply to you, and make informed choices. You can ask your doctor to explain the absolute risk of different outcomes for you and your individual details.

Re-frame the risk

To get the full picture, it can be helpful to reframe the risk.  For example, if 5 out of 1,000 people will die over 10 years, it is also true that 995 out of 1,000 will not die.

Ultimately, you want to know how likely it is that you will be one of the 5 out of 1,000 or one of the 995, and what you can do to improve the chance that you will be one of the 995.

Questions to Ask about Risk

Here are some questions you can ask to make sense of information about health risks.

1. Risk of what? This question helps you understand what the possible outcome is (for example getting a disease, dying from a disease, developing a symptom), and consider how bad it is and how much it matters to you.
2. How big is the risk? This question helps you understand your chance of experiencing the outcome. If you hear about the number of people who experience an outcome, always ask, “Out of how many?” Was it 10 people out of 1000, or 10 people out of 100? You need to know how many people could have experienced the outcome and the number who didn’t in order to work out what your actual chance of having it is. Remember to ask for absolute risk
3. What is the time frame? Is the risk for something that might happen in the next year, the next 10 years, or a lifetime? People often find a risk more important if it could happen soon compared to some time in the future.
4. Does the risk information apply to me? Is the information about the risk based on studies of people like you (people who are your age, race and sex, people whose health is like yours).

More questions that might help

These five questions from Choosing Wisely Australia can also help you have a conversation with your doctor or other health care provider, about risks and benefits of tests, treatments and procedures.

1. Do I really need this test, treatment or procedure?  Tests may help you and your doctor or other health care provider determine the problem. Treatments, such as medicines, and procedures may help to treat it.
2. What are the risks?  Will there be side effects to the test or treatment? What are the chances of getting results that aren’t accurate? Could that lead to more testing, additional treatments or another procedure?
3. Are there simpler, safer options?  Are there alternative options to treatment that could work. Lifestyle changes, such as eating healthier foods or exercising more, can be safe and effective options.
4. What happens if I don’t do anything?  Ask if your condition might get worse — or better — if you don’t have the test, treatment or procedure right away.
5. What are the costs?  Costs can be financial, emotional or a cost of your time. Where there is a cost, is the cost reasonable or is there a cheaper alternative?

Dig Deeper

Let’s explore absolute and relative risk a bit more.

Example 1.

Disease A might affect 2 out of 100 men over their lifetimes.

If a certain drug lowers their risk for the disease from 2 in 100, to 1 in 100, the drug has reduced the absolute risk by 1 person in 100.  Another way to think of it is that you’d need to treat 100 people with this medicine to prevent just 1 person from getting the disease – and 98 of those 100 men who you treated were never going to get Disease A anyway.

Using this example, you could also say that the drug reduced the risk of the disease by 50%, since 1 is half of 2. Looking at relative risk alone, you may think that the treatment is highly effective.  But is it really?  A 50% reduced risk sounds great, but does 1 in 100 sound as good? They are both referring to the same treatment and the same possible benefit.

Example 2.

Let’s look at another example, the impact of eating bacon or processed meats on your risk of cancer. A 20% increase in risk of bowel cancer from eating bacon is widely talked about in the media.

Most media coverage simply states that people who eat higher amounts of processed meat (e.g. bacon, hot dogs, salami, ham) are 20% more likely to get bowel cancer than those who eat less meat. This is technically correct, but also really misleading for those of us who don’t really understand statistics.

First, no baseline rate for bowel cancer is given, so people don’t know what the risk of cancer is increasing from, and what it is increasing to. In the absence of this information, 20% sounds really serious. In fact, the baseline rate for bowel cancer in the research was 40 cases per 10,000 people who consume low quantities of processed meat. That means that each person in this group has a 0.4% risk of developing bowel cancer. The reported increase in risk of 20% might seem to mean that the people in the study who ate lots of red meat regularly will increase their risk of bowel cancer to 20.4%.

But the “20% risk increase” is referring to relative risk. This means that the group of people who ate bacon regularly had a 20% increased risk of cancer compared to those who ate less processed meat. This means that instead of 40 cases per 10,000, there will be 48 cases per 10,000 people that eat more bacon or other processed meats. This is 20% more cases (20% of 40 is 8), but for each person the absolute risk increase is 0.08%, not 20% – a significant difference!

For an “average” person, the chance of getting bowel cancer at some point in their life is about 5 in 100 (5%),  so a 20% per cent relative risk increase in bowel cancer translates to an absolute increase in risk from 5 people in 100 to 6 people in 100.  That change in risk might be large enough for you to decide to avoid bacon, but it might be small enough for you to decide that bacon is worth it!

References:

[i] Elwood, William, cited in Understanding Health Risks – Improve Your Chances for Good Health at  https://newsinhealth.nih.gov/2016/10/understanding-health-risks