Impact of insomnia on health-related quality of life.

With the increased interest in sleep disorders, the definition of insomnia has been refined and extended so that the aetiology of these disorders is considered in addition to their operational characteristics. The International Classification of Sleep Disorders is the most advanced nosology available. It encompasses, although it does not define, the concept that sleep may be disturbed either through disruption of the mechanisms that control sleep and wakefulness, or by factors external to those mechanisms. Formal measures of quality of life invariably include assessment of sleep or the consequences of disturbed sleep, such as fatigue. Generally, when these assessments are used, sleep has been disturbed by external factors, rather than by disruption of the mechanisms that control sleep. Occasional insomnia does not necessarily need medical treatment, but it may nevertheless cost national economies significant sums through absenteeism and sleep-related accidents. Profound, longer term insomnias may arise either because of failure of the mechanisms central to sleep (i.e. as sleep disorders) or as a consequence of medical disorders (i.e. as disordered sleep). These insomnias should be treated, because the former may lead to the development of costlier and more intransigent psychiatric disorders, whereas the latter should be treated for compassionate reasons, within the framework of palliative medicine. Insomnia as a sleep disorder can require either psychological or pharmacological treatment, depending on the diagnosis, whereas insomnia as a symptom may require treatment with newer hypnotics, e.g. zopiclone.