Depression and the aging brain.

impaCt of aging on the epidemiology of depression Depressive disorders among the elderly are a disabling illness that can result in death and need to be properly diagnosed and treated by clinicians. Although the rates of depressive disorders are lower in the elderly than in younger cohorts, prevalence rates are still high and accounts for nearly two percent of all disability in those over 60. Recent data shows that the 12-month prevalence of major depressive disorder (MDD) from ages 65-74 is 3.1% and the lifetime prevalence is 11.7%. 1 Similar to depres-sive disorders in the younger population, females are at higher risk for MDD with a 4.5% 12-month and a 16.9% lifetime prevalence from ages 65-74; whereas, men have a 1.4% 12-month and a 5.1% lifetime prevalence. The prevalence of MDD is highest among non-Hispanic white individuals with a lifetime prevalence of 13.2%, and lowest among African-American elderly, 5.1%. 2 The lower rates of MDD among the elderly are perplexing to many clini-cians. There are several factors to suggest why these rates are lower compared to younger cohorts: 1) older persons may have greater difficulty remembering past symptoms; 2) they may be less psychologically oriented in responding a mental health interview; 3) there may be a cohort effect in younger generations of an increased rate of MDD; and 4) persons who have had MDD may be less likely to live until older age, more likely to be institutionalized, and have more medical comorbidities precluding their participation in epidemiological surveys. Despite these lower rates among the elderly in the community, rates of MDD in primary care settings are high (five percent) and even greater among the nursing home population, 15-25%, and those in acute care hospitals, as high as 12%. 3 impaCt of aging on the risk faCtors for depression Many stressors common to late life serve as important risk factors for developing major depression: physical illness,  limited mobility, sensory deprivation from deafness or blindness, retirement, economic deprivation, poor living conditions , social isolation, rejection by children , as well as loss of spouse. A prior history of depression places elderly patients at substantial risk. It has also been hypothesized that the elderly may have specific physiologic changes that place them at particular risk; these include decreased acetylcholine, dopamine, and norepi-nephrine as well as increased monoamine oxidase. In addition, there are changes in the hypothalamic-pituitary-adrenal axis with increased levels of …