The impact and prevalence of chronic insomnia and other sleep disturbances associated with chronic illness.

Chronic insomnia may coexist with chronic physical and psychiatric conditions, and its prevalence is often higher among patients with these conditions than in the general population. Evidence suggests that insomnia as a feature of chronic disease tends to be more severe and persistent than insomnia that does not occur in the context of chronic illness. Furthermore, comorbid insomnia can have a profound negative impact on patients' quality of life and overall functioning, and may be associated with greater healthcare resource utilization. In some cases, treatment of the underlying disorder may improve sleep, whereas in other cases, treatment of the sleep symptoms may actually improve the underlying disorder. In addition, chronic insomnia may be a precursor to certain psychiatric comorbidities. Further research is needed not only to clarify the efficacy and safety of specific therapeutic approaches but also to further investigate the possibility that successful treatment of sleep disturbances may improve objective and subjective parameters of the disorders themselves. This article reviews the specific associations between chronic insomnia and a wide range of chronic physical and psychiatric disorders.