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Saturday 2nd June 2012

The Jim Clark Rally started yesterday and continues throughout the weekend. It is, apparently, the only closed road rally in the UK. ‘Closed road’ means that the rally stages run over what would normally be public highways but, for the duration of the stage concerned, that road is no longer available to the public and the laws about driving speed and style do not apply.

Though the organisers mount a very large operation to minimise the risks involved there have been incidents where participants have been injured in crashes. Though much less often, there have also been incidents where spectators have been struck by a competitor’s car. And, yesterday, there was, probably, a first when a spectator went into labour and the rally had to be delayed to allow an ambulance to reach her.

Seeing the preparations started me thinking about the central point about prohibition of any kind; who gets to decide what risks an individual can expose himself to and who decides if the risks to others are too great to allow an activity to go ahead?

Prof David Nutt, famously, made a comparison between deaths due to ecstasy and those resulting from horse-riding, for which he coined the term ‘equasy’. I can’t think of a clever term to relate high speed driving with use of the extract of Erythroxylum coca. Carcaine and cocaine definitely isn’t clever.

The issue of who decides what can or should be done to avoid damage to health was in my mind because of a paper in BMJ Open looking at what level of alcohol consumption would minimise chronic disease mortality in England.¹

The authors try to establish the level of consumption that can be shown to be causing harms and then model how much that consumption would need to be reduced in order to minimise those harms.

There is frequently a problem of ‘Chinese whispers’ with scientific papers. The paper says one thing but the press release about it overstates one part and the media coverage latches onto that and makes it ‘sexy’ so that what is reported is not what the research found.

With this paper, strangely, there is an added layer of distortion because the abstract of the paper goes further with its conclusions that the paper itself. The authors conclude, in the full paper, that;

‘It is likely that government recommendations would need to be set at a much lower level than the current ‘low-risk’ drinking guidelines in order to achieve this level.’

But the conclusion of the abstract says;

‘Public health targets should aim for a reduction in population alcohol consumption in order to reduce chronic disease mortality.’

So the authors go from pointing out that current guidelines would need to be greatly reduced to minimise chronic disease mortality to appearing to be calling for action to implement such guidelines.

That point is, of course, what the press took for its headlines with the Guardian, as an example, headlining its report;

‘Cut alcohol intake to just a quarter pint of beer a day, experts advise’ ²

The stories, as you would expect provoked a lot of comment and led to a number of people looking at the study in detail to try and get to what it really had to say rather than what was being reported.

NHS Choices³ does it usual excellent job of explaining the paper and drawing attention to the limitations the authors themselves point out. David Spiegelhalter’s ‘Understanding Uncertainty’ is concerned with pointing out the flaws in the press coverage and also estimating just how big an effect on life expectancy each additional unit of alcohol has. Or, rather, how small because his conclusion is that each extra unit (per week I believe he means) takes just five minutes off life expectancy.⁴

There is one point I want to take issue with Mr Spiegelhalter over, though to be fair to him it was only, really, a passing comment. Statistically, it can be shown that people drinking a certain amount of alcohol have fewer health risks than those not drinking at all. Spiegelhalter says that, if government really wanted to drive harms to the minimum they would have to find ways of getting these non-drinkers to imbibe.

The flaw with the claim that non-drinkers are at greater risk that drinkers, a claim that is widely put forward by drinkers and drink promoters, is that the non-drinkers total includes those who are already so unwell that they cannot drink. I don’t know how many people fall into that category but I do know it means you can’t accept the apparent benefit of being a light to moderate drinker at face value.

There has to be risk in life and suggesting that drinking half a unit of alcohol a day is a realistic way of reducing risk is like saying the Jim Clark Rally should be run with cars limited to a maximum of 20mph. But, of course, if it were it might not be so exciting as to bring on premature labour. 

References

^1.Nichols M, Scarborough P, Allender S, et al. What is the optimal level of population alcohol consumption for chronic disease prevention in England? Modelling the impact of changes in average consumption levels. BMJ Open 2012;2:e000957. doi:10.1136/bmjopen-2012-000957
^2.Cut alcohol intake to just a quarter pint of beer a day, experts advise The Guardian 30th May 2012
^3.Alcohol limit 'should be cut for public health' NHS Choices 31st May 2012
^4.Drinking again Understanding Uncertainty 1st June 2012  

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