The burden of depression is disproportionately higher among older women than older men because of their greater susceptibility to depression and–once depressed–their greater tendency to have persistent depression and their lower probability of death, suggest the results of a longitudinal study.
Clinically significant depressive symptoms affect 8%–20% of community-dwelling older people, and previous research has failed to explain the underlying gender differences, study investigators wrote.
Lisa C. Barry, Ph.D., of Yale University, New Haven, Conn., and her associates assessed those differences in the onset and persistence of depression, as well as in overall mortality. They used data from a 1998 longitudinal study of 754 residents of New Haven aged 70 years and older at baseline. The subjects were followed using detailed in-home assessments every 18 months for up to 6 years (Arch. Gen. Psychiatry 2008;65:172–8).
At baseline, the subjects were a mean age of 78 years. Sixty-five percent of them were women, and 91% were non-Hispanic whites. On average, subjects had a high school education, had two chronic conditions, and were cognitively intact.
A total of 269 subjects (36%) had depressive symptoms at some time during the 6-year study. The prevalence of depressive symptoms was substantially higher among women than men at all time points.
Compared with men, women showed a higher rate of making the transition from nondepressed to depressed status over time. In addition, women showed a higher rate of remaining depressed over time, and a lower rate of making the transition to nondepressed status or to death over time, the investigators said.
“Of course, older men generally have higher mortality rates than older women, irrespective of depression. Nevertheless, the mortality difference we observed by sex was marked, with a nearly threefold difference in the odds ratios for participants who were depressed, compared with those who were not depressed,” the researchers said.
Previous studies may have been unable to detect these patterns because they did not account for fluctuations in depression over time. Rather, they usually included only a single follow-up assessment of depression after a comparatively short interval, Dr. Barry and her associates noted.
In contrast, “the consistency of our findings over four different time intervals provides strong evidence that depression is more likely to persist in older women than in men. [This] is somewhat surprising because women are more likely than men to receive pharmacologic and nonpharmacologic treatment for depression,” they said.
“Whether women are treated less aggressively than men for late-life depression or are less likely to respond to conventional treatment is not known, but should be the focus of future research,” the researchers said.
The investigators added that nearly 40% of the depressed subjects in this study showed symptoms during at least two (and often more) consecutive time points. This finding highlights “the need to initiate and potentially maintain antidepressant treatment after resolution of the initial depressive episode” in this patient population, Dr. Barry and her associates said.
They also pointed out that because African Americans have a higher prevalence of persistent depression than non-Hispanic whites, “future research should explore whether the relationship between sex and transitions across depression states is modified by race, using data that more closely reflect the racial composition” of older adults in the United States.
The study was supported by grants from the National Institute on Aging. The investigators reported no disclosures.