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What do we mean by risk?

Dr Karen Martin
Reviewed by Dr Karen MartinReviewed on 19.10.2023 | 5 minutes read

Doctors talk about risk all the time – it's part of their job to weigh the risks and benefits of giving medication, not giving it, and doing surgery that may help or cause damage. And they talk about these odds as if the best next step is obvious.

But it’s hard to weigh risks before making a decision, and they can mean different things to different people. Let’s turn to the races. Backing a horse with the longest odds to win the Grand National – let's say odds of 100 to 1 – means high risk but potentially high gains. The numbers are fact. But the odds mean something different to everyone: for some, it may be an unacceptable chance of losing your money, but others can only see potential gains, as they’ll win big if the horse does win.

Likewise, any chance of erectile dysfunction may be unacceptable to many men, no matter how low. Others may consider prostate surgery for cancer is worth it. Others may be in the middle – it's acceptable under certain circumstances, such as taking antidepressants, as they can feel better. Still, the side effect can be reversed if they develop erectile dysfunction and want to stop taking the tablets.

It’s true to say that every treatment, surgery, or chance of something happening carries a level of risk – we need to communicate how often the risk happens, how serious it might be, and alternative options.

Let’s talk you through what the medical community means by risk and how we refer to it here. And in any consultation, if you don’t understand something or need it explained differently, don’t be afraid to ask.

How common is common?

We sometimes refer to things as common or rare. There is a distinct classification for these terms, based on risk, and usually used in how often medication side effects occur. Common means a chance of more than 1 in 100 of anyone getting a certain side effect from medicine. You might imagine all the seats filled on a bus, and one person gets the side effect.

This risk can become very common if it’s more than 1 in 10 – think of one person in a busy corner shop.

Rare means a risk of more than 1 in 10,000. You might imagine your target 10,000 steps per day, and just one of these is the risk. Very rare is even less likely to happen than this. Uncommon is if it’s more than 1 in 1000.

A similar scale can be used if you are presented with high risk (equating to “common” or more than 1 in 100 or 1%) versus low risk (“rare” or more than 1 in 10,000 or 0.01%). This scale has varying degrees – moderate (between high and low) and minimal and negligible, both less than low risk.

What about risk over time?

An event may be so rare that we need to add time to our risk estimates. We all know lightning doesn’t strike twice, but the chance of hitting you just once over the average lifetime is 1 in 10,000.

Heart attacks are another good example. Doctors can examine the many factors that can affect people and raise their risk of a heart attack (age, weight, whether you smoke, where you live, certain blood results) and determine a risk that is specific.

A Cardiovascular Disease Risk Assessment (CVDRA) gives a chance in the percentage of you having a heart attack or stroke within the next 5 years. This percentage is useful to urge you to modify any lifestyle factors to improve it, such as losing weight and stopping smoking. If you have a 10% risk or more, this is considered high, and your doctor will offer medication to further reduce your risk.

You will be offered a statin to keep your blood vessels healthier and hopefully protect you from a heart attack or stroke.

How do I weigh up one risk over another?

A good example here is discussing the combined contraceptive pill with women. There’s a risk of blood clots, called venous thromboembolism (VTE), either in your legs (deep vein thrombosis) or lungs (pulmonary embolus). These can be serious - a pulmonary embolus can be life-threatening.

They discuss the risk with you. The risk increases if you are a certain age, if you smoke and if you are obese, among other factors. Certain brands increase the risk, (those with higher estrogen content). Some of these risks are in discussion with you, some are too high for your doctor to safely prescribe no matter your preference, and some may be acceptable to both of you, for example to treat polycystic ovarian syndrome (PCOS) symptoms.

The risk of a clot is extremely low. But the medical community doesn’t want otherwise healthy young women to be put at undue risk.

And this is on a background risk that you may then not take contraception at all, and become pregnant. Pregnancy has a much higher chance of blood clots in itself. And an unexpected or unwanted pregnancy brings a host of other issues, too.

This risk business is complicated, isn’t it?

I’m still confused, what now?

Risks can be further complicated with divisions into serious events occurring, which may be less frequent but carry a risk of perhaps death or disability. Compared to risks that won’t cause significant harm or are reversible, but have a much higher chance of happening.

Risks are difficult to grapple with – as doctors, we find it difficult, too. You may know that you’re a person who prefers graphs or representations on diagrams. Ask your doctor if graphics are available. Give yourself time to digest important decisions, and give your doctor time, perhaps in a follow-up appointment, to find a way of explaining so it makes sense to you for any decision you need to make.

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This article has been written by UK-based doctors and pharmacists, so some advice may not apply to US users and some suggested treatments may not be available. For more information, please see our T&Cs.
Dr Karen Martin
Reviewed by Dr Karen Martin
Reviewed on 19.10.2023
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