The study, published in the November online issue of the American Journal of Public Health, showed that major depression was most prevalent among Hispanics - 10.8 percent -- followed by almost 9 percent in African Americans and approximately 8 percent in whites in this age group.
The odds of depressive disorders among older Hispanics were 44 percent greater than among whites, representing a significantly greater prevalence of major depression, said lead author Dorothy D. Dunlop, research associate professor at the Institute for Health Services Research and Policy Studies at the Feinberg School of Medicine at Northwestern University.
The study, which evaluated almost 7,700 adults aged 54 to 65 for racial/ethnic differences in rates of major depression and examined possible mediators, also found that younger age, female gender, being widowed or divorced, living alone and providing care for a parent each significantly increased the odds of depression.
The strong association of caregiving with major depression is comparable to the well-known risk of depression resulting from the loss of a spouse through death or divorce, Dunlop said.
"This finding points to the potential importance of providing social support for caregivers to reduce the burden associated with this complex role," she said.
All health needs, including chronic diseases, such as arthritis, diabetes, high blood pressure and obesity, as well as functional limitations and health behaviors, were significantly associated with major depression.
Physical limitations were the factor most strongly associated with major depression, more than doubling the odds of depression after other factors had been taken into account, the authors said. The strong association between depression and functional limitation is particularly notable, they said, since such limitations are consequences of disease processes.
Other characteristics that significantly increased the odds of major depression included potentially life-threatening illnesses such as cancer, heart or lung disease and stroke, limitations in activities of daily living, lack of regular exercise and tobacco use.
Having fewer economic resources -- less education, income or wealth; lack of private health insurance coverage or employment - was associated with a greater frequency of depression. Reliance on government health insurance somewhat increased the odds of depression, the authors said.
"Our finding that lack of health insurance coverage is strongly associated with frequency of major depression particularly implicates the need for health insurance carriers to facilitate better access to medical care among ethnic minority groups, Dunlop and colleagues said.
Further, the strong relationship of health needs to depression frequency, including functional limitations and potentially life-threatening conditions, points to the importance of public health interventions involving disease prevention and management, they said.
"Given the clear association between frequency of major depression and greater health burden and fewer economic resources, factors common to older ethnic minority individuals, more effective treatment, public health or public policy programs that increase access to mental health care and general medical care may lead to long-term reductions in racial/ethnic disparities in depression, Dunlop and co-researchers said.
Collaborating with Dunlop on this study were Jing Song and Larry M. Manheim, research professor, Institute for Health Services Research and Policy Studies; John S. Lyons, professor of psychiatry and behavioral sciences; and Rowland Chang, M.D. professor of preventive medicine, medicine and physical medicine and rehabilitation, Feinberg School of Medicine, Northwestern University. All of the authors are researchers at the Multidisciplinary Clinical Research Center in Rheumatology at the Feinberg School.
This study was supported in part by grants from the National Institute of Arthritis and Musculoskeletal and Skin Diseases, the National Center for Medical Rehabilitation Research and the Arthritis Foundation.