Relative vs Absolute Risk of developing cancer

Relative vs Absolute Risk of developing cancer

We often hear of the increased risk of developing cancer due to various activities, smoking, drinking, sun and other radiation exposure and so on. Everyone has an absolute risk of developing cancer, which can be changed by different behaviours which change the relative risk. For example, with a CLL diagnosis, we are at a higher relative risk of certain cancers, such as skin cancers.

'It’s all relative: how to understand cancer risk

Professor Ian Olver explains the difference between "absolute risk" – the risk of developing a cancer over a certain period of time; and "relative risk" – the risk one group of people has of developing a cancer compared to the risk of another group.

The interactive cancer map featured on The Conversation shows that the risk of bowel cancer is 10 per cent higher for men and women who have one standard alcoholic drink every day, than for those who don’t drink any alcohol.

This is known as “relative risk” and does not mean you have a 10 per cent chance of getting bowel cancer if you drink one drink per day.

As the map says, it means your risk of bowel cancer is 10 per cent higher than the risk of someone who doesn’t drink any alcohol.

Prof Olver says this 10 per cent matters not only in relation to someone else, but also in relation to the absolute risk of getting the particular cancer in the first place. If the absolute risk is small, then a 10 per cent increase still doesn’t make your chances of getting cancer very high.

“For instance, a man living in Australia has an absolute risk of 10 per cent of developing bowel cancer over his lifetime. If he drinks one beer every day and his risk of bowel cancer increases by 10 per cent, then it only goes up to 11 per cent overall – so not much higher than it was in the first place,” he says. '

w3.unisa.edu.au/unisanews/2...

The interactive cancer can be found here or via a reference from the above article: theconversation.com/interac...

Neil

Photo: Too hard to wrap your head around? Have a rest in the shade on the rim of this dormant volcano

6 Replies

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  • Neil, I need the rest after that mathematical display. My head swims with such statistics. How 10% and 10% equal 11% is beyond my comprehension. I have Mental block when it comes to math.

    So thanks for the dormant volcano rim shelter.

  • Sitting comfortably in the shade? I think the choice of two 10 percents confuses matters.

    Say there's an absolute risk of a specific cancer which is 10%, and you engage in some behaviour that increases your risk by 20%, relative to someone who doesn't engage in that behaviour, then your new risk is the absolute risk of 10% plus a further 20% of 10% or 2% from your risky behaviour. That's (10% + 2%) or 12% in total, NOT 10% + 20%. The risk of some cancers (like CLL) is already quite small, so even a 100% increased risk (double the risk) of a low risk cancer can still be quite small. But as we know when we are diagnosed with CLL, if you happen to be the person who is unlucky enough to realise that small risk, it can be life changing, so it's worth being aware of what increases risks and avoid them where possible, particularly where the absolute risk is already high.

    Hmm, that seat's long enough for the two of us - move along as I'm sure more will be joining us :) .

    Neil

  • Yeah, I get that risks are there and relative, and I can grasp the need to be aware and take a bit of caution.

    And, now I absolutely will move along from this subject. 100% of my brain is fried and 85% of my rear is numb.

    : )

  • I need a drink now and I'm 100% certain of that! :-)

    Newdawn

  • I'm with Newdawn on this one too! :) Good reading. Nice to know that the one beer is no big deal!

  • Really clear explanation, thanks.

    Love the photo and would like to be there. But I'm in the UK :-(

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