Nearly 60 percent of the nation's elderly have trouble sleeping, whether it's a lot of tossing and turning or outright bouts of insomnia. While for most people sleeplessness can be annoying at best or unhealthy at worst, for elderly individuals who have suffered from depression in the past, poor sleep may be the first sign that a new bout of depression is coming on.
In a study to be published in an upcoming issue of the American Journal of Psychiatry and currently available online, UCLA professor of psychiatry Dr. Michael Irwin and his colleagues posed three hypotheses: risk for depression would be higher among older people with a prior history of the disorder; among those with prior depression, sleep disturbance could predict a relapse or recurrence; and sleep disturbances could act as a risk factor for depression recurrence separate from other depressive symptoms. The study confirmed all three hypotheses.
"Insomnia is the most frequent sleep disturbance in depressed patients and is viewed as a symptom of current depression," said Irwin, who also directs the Cousins Center for Psychoneuroimmunology at UCLA's Semel Institute for Neuroscience and Human Behavior. "But when sleep disturbances begin to emerge in an otherwise healthy adult who has experienced depression in the past, we found that it may serve as a precursor to another attack of depression."
The study looked at 351 adults, age 60 and older. Of that number, 145 had a prior history of major or non-major depression that was in full remission, while 206 had no prior history of depression or other mental illness. The participants were assessed at four different times over a two-year period for depressive episodes, depressive symptoms, sleep quality and chronic medical disease.
The researchers found that of the subjects with prior depression, 23 had a relapse, compared with only one person in the group without prior mental illness. With the first group, researchers were able to predict depression recurrence based on individuals' sleep disturbance. Irwin noted that this association was established independently of other depressive symptoms, chronic medical disease or any use of antidepressants.
The study, Irwin said, is the first to demonstrate that sleep disturbances act as an independent risk factor for depression recurrence in older adults.
"Unfortunately, sleep difficulties are often considered to be a part of normal aging, and asking about and assessing the quality of an older person's sleep is frequently overlooked during routine doctor visits," Irwin said. "The omission is particularly striking, since we know that sleep disturbance is associated with declines in health functioning and with increases in all causes of mortality in older adults.
"And now, this study shows that sleep disturbance is often related to depressive disorders in late life, which carry further considerable risks for morbidity and mortality."
To identify older adults at risk for depression, Irwin said, a two-step strategy can be employed. One step involves assessment of whether individuals have had a prior episode of depression, the other whether they have current and ongoing sleep disturbance.
"Given that sleep disturbance is a modifiable risk factor," he said, "these findings tell us that we need to develop treatments that target sleep disturbances for the prevention of depression recurrence in older adults."
In addition to Irwin, other authors of the study included Hyong Jin Cho, M.D., Ph.D.; Helen Lavretsky, M.D.; Richard Olmstead, Ph.D.; Myron J. Levin, M.D.; and Michael N. Oxman, M.D.
Levin reports receiving funds from pharmaceutical company Merck & Co. Inc. The other authors report no competing interests.
Funding for the study was provided by grants from the National Institute on Aging, the National Institute of Mental Health; and the Cooperative Studies Program of the U.S. Veteran's Affairs Office of Research and Development.
The Cousins Center for Psychoneuroimmunology at UCLA encompasses an interdisciplinary network of scientists working to advance the understanding of psychoneuroimmunology by linking basic and clinical research programs and by translating findings into clinical practice. The center is affiliated with the Semel Institute for Neuroscience and Human Behavior and the David Geffen School of Medicine at UCLA.