Stressors Across the Lifespan and Dementia Risk: A Statistical Method Analysis

Abstract

The Cache Lifespan Stressors and Alzheimer's Disease (LSAD) study has access to data from the Cache County Study on Memory Health and Aging (CCS) that have been linked to the extensive genealogical and vital records from the Utah Population Database (UPDB). Information about stressful life events experienced by the original 5092 CCS participants has been extracted objectively from the UPDB, without the possibility of recall bias. This information was then statistically analyzed to look for relationships between key stressors and dementia risk. The LSAD study made it possible to examine the correlation between stressors as well as look at patterns or groupings that may exist among the stressors. For this project, we will apply, compare and contrast a variety of methods to explore the relationship between stressors and dementia status. We first assessed significant associations between stressors and dementia using chisquare tests, logistic regression, and stepwise logistic regression. CART and Random Forests were also used to evaluate which variables are most predictive of dementia status. To explore interrelationships among the stressors, principal components analysis, factor analysis, and cluster analysis were performed. These last methods also obtain dimension reduction of the set of stressor variables to a smaller set of factors or clusters of stressors. For each of the methods, we explored some basic strategies to account for the high rate of missingness among some of the stressors. Introduction The proportion of elderly adults is expected to increase significantly both in the U.S. and worldwide. With that increase the number of adults with dementia will also grow. The costs of treatment and caregiving for individuals with dementia are significant, and the growing prevalence of dementia represents an increasingly enormous health burden. There is a pressing need to explore and better understand the causes and risk factors associated with dementia, to provide better means of prevention, diagnosis, and treatment. Prior research has long suggested that stressful life events may have a significant impact on outcomes in late life. This relationship led to the development of the so-called Holmes-Rahe Stress Index, which has been used to evaluate a person's risk of various illnesses such as headache, diabetes, fatigue, hypertension, chest and back pain, ulcers, infectious disease based on the stressful events, or stressors, they have experienced in the last 1-2 years. Though this measure is widely used throughout the social sciences, the short amount of time it covers is a considerable limitation. With respect specifically to dementia, research has shown that high levels of glucocorticoids released in the brain during stressful situations can lead to damage of parts of the brain responsible for learning and memory. The neural degeneration resulting from the damage to the brain due to the response to stress may increase susceptibility to dementia. This etiology is consistent with findings from various observational studies, which have demonstrated an association between dementia risk and stressors such as death of a parent during 8/10/11 4:46 PM