ABC of sleep disorders. Impact and epidemiology of sleep disorders.

We know that one in seven Americans have a chronic sleep/wake disorder, and although similar data are not available for other Western countries the figures are probably similar. In developing countries factors such as poverty have a profound influence on sleep. In India, for example, it is estimated that one third ofthe population goes to sleep where they are standing when it is time to sleep. Europe has the highest proportion of elderly people, in whom many sleep problems, such as insomnia and sleep apnoea, are more common. When taken together with the fact that hypnotics are among the most widely prescribed drugs, the impact of sleep disorders and their treatment merits particular attention in Western society. The United Kingdom, however, has lagged behind other countries in terms ofdeveloping specialised facilities for treating sleep disorders. At present the impact of sleep disorders on morbidity and mortality is not widely appreciated. This article provides basic information about the epidemiology of a range of sleep disorders and highlights some of the implications of sleep disorders.