Assessing Modifiable Risk Factors for Cognitive Decline: Widowhood and Subtypes of Affective Symptoms

This doctoral thesis assesses the role of widowhood and subtypes of affective symptoms as possible risk factors for cognitive decline. Part 1 is a systematic review and meta-analysis on the effect of widowhood on cognition. The review explores the effect of widowhood (vs. being married) on cognition, not only cross-sectionally but also longitudinally, assessing whether widowhood is associated with steeper declines in cognition over time. Furthermore, the review tentatively explores whether length since spousal loss moderates the relationship between widowhood and cognition. Findings from this review may inform bereavement support programmes. Further clinical implications and suggestions for future research are also discussed. Part 2 is an empirical study that utilises data from the PROTECT study. A Latent Class Analysis (LCA) was conducted to identify subtypes of co-occurring affective symptoms on the PHQ-9 and GAD-7. Multiple linear regressions were conducted to assess for associations between class membership and cognitive decline over a 2-year period, while adjusting for known risk factors for cognitive decline. Findings from this review help to clarify the nature of the relationship between affective symptoms of depression and anxiety, and cognitive decline, and may help to identify specific subgroups of adults over the age of 50 who may be at particular risk of cognitive decline, based on their patterns of co-occurring affective symptoms. Part 3 is a critical appraisal of the process that was undertaken for the literature review and the empirical paper. Reflections include the impact of the COVID-19 pandemic, and the challenges associated with conducting a secondary data analysis

Using Developmental T&E to Inform Operational T&E Decision-Based Analysis

We describe two-stage sequential experiments that are used in building and testing valid simulation models. In the first stage, preliminary samples are taken to estimate performance and inform the parameters for the experiments in the second stage. These two-stage experiments can be mapped to test and evaluation (T&E) by having the first stage applied to developmental test and evaluation (DT&E) and the second stage applied to operational test and evaluation (OT&E). By considering DT&E and OT&E as part of a combined two-stage experiment, we can better leverage the results of DT&E to inform OT&E.Naval Postgraduate School Acquisition Research Progra