Vascular Depression: An Early Indicator Of Decline

Women over the age of 80 represent a rapidly growing demographic group. While older women live longer than men, they do so with more years of disability and frailty. The emergence of geriatric disorders such as vascular disease, depression, frailty and cognitive decline in the aging US population place additional strain and expense on the already over-burdened public health care system. Meanwhile, integrated models of care are associated with preserved functional independence, reduced medical costs, and greater satisfaction for both health care providers and patients. Implementation of integrated care demands process-models of disease that contextualize symptoms within broader patterns of decline. This dissertation proposes a model representing a hypothesized late-life clinical trajectory following from high cerebrovascular burden. The hypothesized trajectory includes higher rates of depression (of vascular origin), cognitive decline, frailty and shortened remaining lifespan. Different facets of this model are tested in the four studies that comprise this dissertation. The sample was drawn from the Health and Retirement Study; a longitudinal, demographically-representative data sample of older adults in the United States. The sub-sample used in this dissertation included 1,368 stroke-free women over the age of 80 at baseline (1998). This sub-sample was followed for 10 years. The first study tested the hypotheses that high CVB predicts greater depression symptoms, and that brain reserve (i.e.: education) protects elders from developing depression symptoms. A latent growth curve was used to identify differences in depression at baseline and over time based on CVB, cognitive functioning, education and age. Results indicate that at any level of CVB, older women with more education experienced fewer depression symptoms. Results support brain reserve theory and the vascular depression hypothesis. These results suggest that having greater education may postpone development of clinically-significant depressive symptoms resulting from high CVB, thereby preserving mood in late life. The second study tested the hypothesis that variables representing the three domains of Rowe and Kahn\u27s Healthy Aging framework predict longevity in this sample of stroke-free women over the age of 80. The avoidance of disease domain was characterized in this paper as CVB - chronic comorbidites that slowly erode adaptive functioning over many years. The sustained engagement criteria was conceptualized as depression, and deficits in the preservation of cognitive and physical functioning domain were identified as rapid cognitive decline. We found that at most waves (2002, 2004, 2006) mortality was predicted by CVB, depressive symptoms and cognitive drop measured 2 years prior. CVB and depressive symptoms at the 2000 wave predicted mortality at 6 and 8-years. Older women with the greatest longevity had low CVB, robust cognitive functioning and few depression symptoms, supporting successful aging theory and terminal cognitive drop. The third study tested the hypothesis that vascular depression is a prodrome for frailty. At baseline, the prevalence of frailty was 31.5%. Over a 4-years the incidence of frailty was 31.8%. After controlling for age, education, ADL and IADL functioning, arthritis, pulmonary disorders, cancer, and self-rated health, vascular depression significantly predicted new cases of frailty. These findings suggest that vascular depression is a prodrome for frailty. The fourth study tested the proposed model using structural modeling. The model demonstrated good overall fit and a significant indirect pathway from vascular depression to mortality through frailty was identified. Results support the proposed theoretical framework and suggest that vascular depression symptoms are associated with a clinical trajectory including more frailty symptoms and shorted remaining lifespan. This finding supports integrated care for geriatric patients and suggests specific targets for intervention with older patients experiencing vascular depression symptoms