Sleep problems are reported by many elderly patients with major depressive disorders. However, these problems do not always coexist, even though they share similar risk factors. Insomnia is often associated with dependence on sleep medications, chronic fatigue, and increased risk of falls. Chronic sleep disturbances may lead to nursing home placement. Cricco and associates investigated the relationship between self-reported insomnia and cognitive function in elderly adults.

Patients were selected from participants in the Established Populations for Epidemiologic Studies of the Elderly. Patients who were at least 65 years of age and cognitively intact at baseline were included. Various demographic data were collected. Education levels, physical function, depressive symptoms, and a mental status questionnaire were reviewed. A variety of questions about sleep disturbance were included, with insomnia defined as “trouble falling asleep or trouble with waking up too early and not being able to fall asleep again.” If the patient had insomnia at baseline and at the third annual follow-up, he or she was categorized as having chronic insomnia. Patients with symptoms only at the follow-up visit were categorized as incident cases.

There were 6,444 patients (2,429 men and 4,015 women) included in the study. Of these patients, 27.2 percent of the women and 21.0 percent of the men were categorized as having insomnia. Prescription sleep medications were used in 8.2 percent of the women and 4.8 percent of the men. Depression was most likely to be noted in patients with chronic insomnia and least likely to occur in those without chronic insomnia (with an intermediate prevalence of depression in those who were classed as incident cases of insomnia). Cognitive decline occurred in 26.8 percent of women and 25.5 percent of men during the three-year follow-up period.

Among the male participants, insomnia was an independent risk factor for cognitive decline, regardless of whether the man also had a depressed mood. Specifically, a nondepressed man with chronic insomnia was nearly one half as likely to show evidence of cognitive decline as the men who did not have insomnia at the three-year follow-up visit. In women, chronic insomnia was associated with cognitive decline only if the participant also had high levels of depressive symptoms.

The authors conclude that chronic insomnia is an independent risk factor for cognitive decline in patients 65 years and older, especially in men. Depression and insomnia did not seem to contribute synergistically to cognitive decline, although each was independently associated with poorer scores on the Short Portable Mental Status Questionnaire.

editor's note: It is incumbent on the physician to recognize and treat complaints of chronic insomnia in elderly patients, knowing that maintenance of cognitive function may be one positive byproduct.—g.b.h.