Narcolepsy and car accidents

In an article about narcolepsy (Health, 10 June), we reported the statement that daytime sleepiness caused by narcolepsy and other sleep disorders is the commonest cause of fatal car accidents. We are now informed that this is wrong. Narcolepsy, which is a rare sleep disorder, is not a common cause of car accidents, although daytime sleepiness caused by shiftwork, insomnia and other problems is a factor in about a quarter of motorway accidents.