For most of my life I have had no difficulty in sleeping, rather in staying awake. But whether because of a physiological ageing process, or of a guilty conscience aware of a life of cumulative sin, I now experience periods of insomnia. Occasionally I do what I once swore as a young man never to do: I take sleeping tablets.
My favourite, to the exclusion of all others, is Zolpidem (Ambien). It does not leave me feeling groggy, as do other hypnotics, but rather as near to daisy-freshness as I ever feel early in the morning. Imagine my alarm, then, when I saw an article in a recent New England Journal of Medicine that suggested that the drug of my choice might make me a dangerous driver the following day.
Zolpidem is short-acting, which means that it is metabolised and cleared from the body quickly. Some people therefore find that they wake in the middle of the night when they have taken it (previous studies suggest that Zolpidem’s main advantage over placebo is in getting people off to sleep quickly). Having woken in the night, and finding difficulty in returning to sleep, some people are tempted to take more of the drug. Indeed, the manufacturers – the largest company listed on the French stock exchange – have thoughtfully manufactured a lower-dose pill for precisely this situation.
But simulated driving tests done on people after they have woken in the morning having taken Zolpidem demonstrate that they perform less well than people who have taken nothing. This is so even when people claim to feel no after-effects of the drug at all: in other words, they are not the best judges of whether or not they suffer such after-effects. The commonly-heard refrain, principally from middle-class hypochondriacs, that “I know my body” is not true in all, perhaps in many circumstances.
However, the article does not address certain important questions concerning the effect on Zolpidem on driving the following day. The first is that while Zolpidem may reduce performance on simulated driving tests, it is known that insomnia itself does likewise. So the question is not whether Zolpidem affects driving tests, but whether it affects driving tests among those who suffer from insomnia and who take it. In such circumstances, it is conceivable that it improves performance.
The second point not raised in the article is the extent to which worse performance on simulated driving tests translates into accidents in the real world, and if it is translatable, the size of the increased risk, particularly of serious accidents. For example, a paper in the Lancet not long ago about the dangers of various psychoactive substances had a table that showed that, in France, 30 percent of fatal road accidents were associated with or caused by alcohol intoxication while 3 percent were associated with or caused by cannabis intoxication: such that, if there are 10 times as many drunk as stoned drivers on French roads (a not unlikely supposition), cannabis is as dangerous as alcohol.
No such epidemiological statistics for Zolpidem anywhere in the world are given in the article. The dangers of taking Zolpidem and driving the following day were therefore necessarily extrapolated or inferred from laboratory data, reasonably enough in the circumstances, but far from constituting satisfactory proof.
From my reservations about the article you may well have gathered that I have every intention of continuing to take Zolpidem from time to time and of driving the morning after. Until I know the size of the effect, not in the laboratory but on the roads, I shall not change practice. Besides, as many a drunk has said to me, “Drink doesn’t affect me like it affects others, doctor.”
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