A new study published in the American Journal of Psychiatry has found that poor sleep may be the first sign of relapse of depression for elderly individuals who had depression in the past.

“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,” says lead researcher Michael Irwin, MD, a professor of psychiatry at UCLA.

The study included 351 participants, all of whom were 60 years of age or older. The researchers posed three hypotheses, all of which were confirmed through the study. Those hypotheses were: 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 relapse or recurrence; and sleep disturbances could act as a risk factor for depression recurrence separate from other depressive symptoms.

“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 says. “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.”