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.