Alcohol & Mouth Cancers.

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A local news outlet ran with a story recently that said research had shown that increased alcohol consumption lead to increased mouth cancers.

The trail to try to find the supporting research lead back to a UK cancer body but a request for a reference went unanswered.

The report (SBS News) said that over the last 30 years alcohol consumption had gone up and so had the incidence of mouth cancers. Ergo, drinking increases your chances of mouth cancer. The stated increase was 25%.

Sounds scary. But what if the chance had gone from 1 in a million to 1.25 in a million.

Not quite so scary.

And what else has changed over the last 30 years with things that go into people's mouths?

The Western diet has dramatically increased its consumption of chilli, a known mouth irritant.
Much more processed food.
Much more junk food.
Many more novel food additives, such as artificial sweeteners.
Vegetable consumption has decreased.
Fruit consumption has decreased.
Oral sex has, anecdotally, increased. (human papilloma virus (HPV), is a known carcinogen.)
Beer consumption down, wine consumption up.
Genetically modified foods introduced.

To mention just a few.

I will take their survey just a little more seriously when they can tell me how they allowed for these other changes.

And who paid for the research. And why.
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Prostate Cancer and Red Wine

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The Australian media was abuzz last week with a report that alcohol consumption increases the chances of prostate cancer. Two drinks a day will increase your risk by 20%. The risk increased with the number of drinks consumed in a day.

Before I pour my home brew down the drain, there are a few things I need answered.
(If you haven't read my previous post, now's a good time. I'll wait.)

Causality
Could alcohol consumption cause/increase the risk of prostate cancer? Possible.
Could prostate cancer risk cause drinking? Improbable.
Could a third factor be in play? Possible. Here are a few possible other factors:

People who drink large amounts of alcohol a day are often overweight. Is BMI a factor?
The consumption of chips, nuts and snack foods is probably proportional to drinks consumed.
Big drinkers often eat more meat.
Is consumption of other foods an issue - fibre, greens, fruit?
Do drinkers live longer, due to the heart benefits of alcohol, and get cancer due to longevity?

That will do. I'm sure we could come up with more. You can begin to see the difficulty of extracting two issues from a very complex life-matrix.

Crud Factor
Is a crud factor in play? Possibly. Sometimes a big survey like this finds statistical significance where no practical significance exists or will average out differences in reports.

Compare the following two extracts from studies into prostate cancer and alcohol consumption:

Our present study suggests that consumption of beer or liquor is not associated with prostate cancer. There may be, however, a reduced relative risk associated with increasing level of red wine consumption. Int. J. Cancer: 113, 133–140 (2005).

Wine or beer consumption was unassociated with prostate cancer; however, moderate liquor consumption was associated with a significant 61–67% increased risk of prostate cancer. International Journal of Epidemiology 2001;30:749-755

Looks as if beer is neutral, red wine gets a sort of a plus and spirits get a sort of a minus.

So does the report mean anything?

Too early to tell really but I will put a punt on the benefits of moderate alcohol consumption outweighing the possible down side.
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Of sharks and ice-creams...

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Really this post is about statistics but you wouldn't have come if I had said that.

The thing is that there are reports published everyday on every possible subject, many of them food and health linked. My next post, which prompted this pre-post, is on prostate cancer and red wine. I am doing this post separately as I think I will be referring to it time and time again.

Newspapers happily publish these 'shock-horror' health reports, edited, cherry-picked, sensationalised and often unverified.

Readers, knowing no better, accept them on face value.

To help me explain, let me now call on some sharks and ice-creams.

Sharks & Ice Creams - the pursuit of causality.
There has been shown to be a strong correlation between shark attacks and ice-cream consumption in Australia.

Does that mean eating ice-creams make you more prone to being eaten by a shark?

Does it mean that, having been attacked by a shark, you start craving dairy food?

Or could it possibly be that a third thing, maybe the season, is controlling both things?

Indeed it is the case that it is in summer that both shark attacks and ice-cream consumption increase.

Independently.

Causality is fundamental to interpreting any report. What caused what? Whenever you see a report in the papers linking two things, ask yourself the following three questions:

• Is A really causing B, as claimed?
• Could B actually be causing A?
• Could something else, C, be causing both A and B?

The Crud Factor
The crud factor in statistics is an acknowledgement that everything is correlated.

If I was to find the data for tin production in Bolivia for the last ten years and also find the number of deaths in bicycle accidents in Belgium over the same period and plot them on an X-Y graph there would almost certainly be a correlation between the two.

A chance correlation.

It may be negative, it may be positive, it may be big or small, but it is most unlikely to be zero.

That is why all scientific research needs to be replicated; scientists test the same hypothesis (that tin production in Bolivia is impacting on bicycle fatalities in Belgium) using different data. If they can replicate the results then their confidence in the hypothesis increases.

It is not uncommon for replicate testing to fail to reproduce the original work.

Sadly, journal editors are not as keen to publish a negative result as they are to publish a positive and interesting one and such work often never gets beyond the waste bin. And, should they publish an article negating previous work, news media are far less likely to run it because it is not "news" and not shocking enough.

Summary
So, if there is a news item showcasing some horror relationship between a food and health or even some wonder cure, be ready to ask yourself if the implied causality makes sense and could it just be a chance correlation.

There you go. That didn't hurt, did it?
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