It’s all Relative…

Wow, it’s hard to believe that it’s been about a month since I last posted to this blog. Despite all of my good intentions, somehow the time just seems to have gotten away from me. More than once I have pondered, now that I am notionally “retired”, how in the world did I ever find time to hold down a full-time job!

I guess like all things in life, it’s all relative…

Which brings me to the subject of today’s post. I was having lunch a couple of weeks ago with a former colleague who I have not seen for quite a number of years (one of the perks of now having some time to catch up with old friends!). We got to talking about how difficult it is to maintain an even keel about the promise of cancer research, when the natural tendency is to want to celebrate, even to the extent of often over-hyping preliminary results that are still a long way away from the clinic.

Researchers, after all, need to be able to support their research by convincing granting agencies to fund them, and granting agencies need to justify their own success by keeping themselves in the public eye, especially for those that are charitable organizations dependent on public trust, enthusiasm and donations. Even government funding agencies need to be accountable to their paymasters and compete for ever diminishing funds.

This is a very difficult tightrope to walk, and I know this from personal experience. More than once, I have been very uncomfortable about granting an interview to the press on a result that, while brimming with excitement and potential, was a long way away from being of proven value in the fight against cancers.

But it is very difficult to get that even-handed message across, even when you want to, because the media are not interested unless there is a bit of a sensationalist angle to the story.

There is also a big problem with the perception of the reader or the listener or the viewer. One of the biggest problems comes in the area of non-scientists trying to understand the concept of risk, especially the difference between absolute risk and relative risk. Let me illustrate the problem.

Suppose you read in a headline that a new discovery shows that factor X leads to a 30% increase in the risk of a particular cancer. On the surface, such a huge increase in risk would likely take the reader aback, and possibly create significant fear or concern, especially if factor X was something you personally identified with. And indeed a 30% increase in relative risk might well be significant. But it also may be almost insignificant in the overall scheme of things.

How so? It all depends on what is the ABSOLUTE risk in the first place. For example, if the absolute risk in the first place was one in a million, then a 30% increase raises the stakes all the way to 1.3 in 1 million. I don’t know about you, but I don’t think I’d be losing one wink of sleep over such an increase when the probability is so minuscule in the first place. This is why we have to be extremely careful about how we report numbers and percentages and risks. Now if you tell me that my risk of something just went from 1 in 10 up to 3 in 10, then that indeed is a very significant increase and one that would cause be to have great concern. But that jump is far in excess of a 30% higher risk, and in fact is a threefold increase in absolute risk.

I don’t want to belabour the point, but really to drive home the message that one must look at every headline, not with a grain of salt, but with the wisdom of having an inquiring mind, and asking what is this really telling me? Often times what you think it is telling you is in fact what the writer or the editor WANTS you to come away with, and may or may not be the accurate message that you OUGHT to be coming away with.

In other cases, it may not be a case of hyperbole or any intent to mislead, but simply that the subject matter is complicated and requires the reader or the listener to really think carefully about the data that is being presented.

     
 
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Comments

It’s all Relative… — 2 Comments

  1. Let’s say I’ve had a heart attack. What kind of absolute risk reduction do I have if I take a statin?

  2. Hello Dave,

    I’m afraid I am 100% unqualified to be able to answer that question. I do know that the use of statins has come under a lot of pressure and criticism lately since studies are clearly showing that there is far less benefit from them for the prevention of heart attacks in people with high cholesterol who have not had any heart attack. Where I do believe that the evidence is more robust is that statins probably do prevent SECOND heart attacks, perhaps by as much as 1/3 compared to non-statin users.

    But that is not the answer to your question. I have no idea about the absolute risk of heart attack in statin or non-statin users for people who have already suffered a heart attack. I’m afraid you need to discuss this with an expert or your cardiologist.

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