Insomnia may perpetuate depression in some elderly patients

In addition to being a risk factor for a depressive episode, persistent insomnia may perpetuate the illness in some elderly patients, and especially in those receiving standard care for depression in primary care settings, according to a study published in the April 1 issue of the journal SLEEP.

The study, authored by Wilfred R. Pigeon, PhD, assistant professor of psychiatry at the University of Rochester Medical Center in Rochester, New York, focused on 1,801 elderly patients (60 years of age or older) with major depressive disorder and/or dysthymia who completed a prior clinical trial for treating depression called Project IMPACT. Dr. Pigeon’s study assigned those same subjects to an insomnia status group: persistent, intermediate, and no insomnia, based on insomnia scores at both baseline and three-month time points.

Logistic regressions were conducted to determine whether persistent insomnia was prospectively associated with an increased risk of remaining depressed and/or achieving a less than 50 percent clinical improvement at six and at 12 months compared with the no insomnia reference group. The intermediate insomnia group was compared with the other two groups to determine whether a dose-response relationship existed between insomnia type and subsequent depression.

According to the results, patients with persistent insomnia were 1.8 to 3.5 times more likely to remain depressed, compared with patients with no insomnia. The findings were more robust in patients receiving usual care for depression than in patients receiving enhanced care. The findings were also stronger in subjects who had major depressive disorder as opposed to those with dysthymia alone.

Dr. Pigeon noted that these results are in keeping with prior longitudinal studies indicating that insomnia was a risk factor for both first and recurrent episodes of major depression. The present study adds to this body of literature by providing evidence that insomnia may also serve to perpetuate depression that is already under way, added Dr. Pigeon.

“Even when depression was identified and treated in the primary care setting, the older adults in this study were more likely to remain depressed if they also exhibited persistent insomnia. The finding that this risk was higher in the usual-care group suggests that enhanced depression care may partially mitigate the perpetuating effects of insomnia on depression,” said Dr. Pigeon. “While the findings make intuitive sense, until relatively recently insomnia was often considered a symptom that dissipated without active intervention once a primary condition like depression was treated, instead of being considered a distinct clinical entity that might affect a primary disorder. This study has several limitations, not the least of which are that it is not a causal study nor does it unequivocally answer the question of whether insomnia that presents with depression is a symptom or a co-morbid disorder. What seems most likely is that insomnia is indeed simply a symptom in some cases, but clearly a disorder requiring its own treatment focus in other cases.”