The Doctor’s Surgery
Health puritans are like the poor – always with us. So it is pleasing when the puritans suffer defeat, even if only temporarily (all their defeats are temporary).
A recent paper in the Lancet, a publication that can hardly be accused of habitual subversion of received ideas, showed that lowering the legal limit of alcohol while driving did not, contrary to expectation, reduce the death rate from road traffic accidents in Scotland.
I do not go as far in this matter as a friend of mine. He says that it is wrong in principle to punish people for accidents they might cause while under the influence of alcohol rather than for accidents they have actually caused while under its influence.
It is, of course, a fact that the great majority of drunk drivers get away with it and most reach their destinations in perfect safety. Perhaps this would also be true of airline pilots.
Still, I recall with shame my young adulthood when I would sometimes drive when I could hardly stand up straight. It was not that I disbelieved it was dangerous to do so. It was rather that, at the time, I thought it was clever and almost witty to drive while incapable of walking without staggering. One is entitled to endanger oneself (although there might be limits even to this entitlement), but not to endanger others.
In 2014, Scottish law reduced the legal limit of alcohol in the blood by three eighths. It seemed to stand to reason that this should reduce the fatal road accident rate because the rate of such accidents after drinking increases in proportion to the amount of alcohol in the blood.
But what stands to reason in theory is not always a reliable guide to what happens in practice: indeed, if anyone says, ‘It stands to reason,’ you may be almost sure that he is going beyond the evidence.
The impressive thing about this paper is that it takes into account long-term trends rather than merely claiming that, since a happened after b, a was caused by b. (Everyone knows that the homicide rate in America rose after Prohibition, but few know – or care – that it rose at the same rate before Prohibition.)
Of course, the fact that the number of fatal road accidents did not fall after the law was passed has more than one possible explanation. Perhaps the Scots did not obey the law – and, naturally, there were calls for stricter enforcement. But this might not be the explanation because sales of alcohol in bars and pubs (a fertile source of drunk drivers, after all) actually fell during the period, suggesting that it was possible that the Scots did actually take notice of the law. But here, as elsewhere, other explanations are also possible (life is a labyrinth of possible explanations).
One thing strikes me as very unlikely: that, as a result of this paper, there will be much public pressure to raise the legal limit to its former level.
We like to follow the evidence except when the evidence leads us to where we do not want to go, in this case to marginally less strict control of the population.
After all, you never know; it is always possible these days that, on statistical re-analysis of the very complex data, an opposite conclusion to the original might one day be reached. And if it were, think of the opprobrium that would descend on the head of whoever acted on the first interpretation!
There is more rejoicing in the kingdom of epidemiology over the saving of one life by prohibition than over the pleasure of 99 ordinary men given permission to enjoy themselves.