Association between chronic insomnia and depression in elderly adults.

Insomnia is not just a common symptom of various psychiatric or physical disorders, but is itself categorized as a primary psychiatric disorder. Aside from the manifestations of difficulty initiating sleep, fragmented sleep, early-morning wakenings, and overall poor sleep efficiency, the subjective feeling of inadequate or non-restorative sleep the next morning, as well as psychosocial distress or dysfunction caused, are even more crucial in the diagnosis of insomnia. The duration of insomnia required for diagnosis as “chronic” has varied from as little as 1 month to as long as 6 months, depending upon the criteria used. The increased incidence of chronic insomnia has been related to concomitant medical and psychiatric disorders, which are frequently present among the elderly. When insomnia becomes chronic, it will invariably increase medical problems significantly, and impact a patient’s quality of life, cognitive and psychosocial function adversely, while further exaggerating the already existing psychiatric or medical conditions. Somatic comorbidities associated with aging are known to be risk factors for insomnia and depression. Therefore, chronic insomnia will further aggravate the heavy burden of medically ill elderly patients and their caregivers. The prevalence of insomnia among the general adult population is approximately 6% to 30%. Furthermore, an estimated 50% to 70% of all people aged 65 years have reported at least one condition of chronic sleep disturbances. A study conducted in one district of metropolitan Taipei, Taiwan has shown that nearly half of the elderly reported suffering from insomnia and poor sleep quality, and 22% of elderly subjects used medication for sleep, numbers that are consistent with results of previous studies in other countries. In this study, 7% of the elderly have possible depression. The severity of depression has also been found to be a significant factor related to their insomnia and sleep quality. Major depressive disorder (MDD) and insomnia are closely and multifacetedly related, and they pose a bidirectional relationship. The interplay between these psychopathologies is not fully understood; however, their functional relationship has become a focus of recent investigation. By using self-rating scales, epidemiological surveys have demonstrated the significant association between chronic insomnia and depression in young adults, as well as in elderly populations. Insomnia is the major complaint among those patients with MDD, and about 40% to 80% of such patients complained of insomnia, or poor