Disease and other dementias are not only a major cause of morbidity and mortality in older populations, but also costly to the healthcare system. Understanding the use of healthcare for this population is critically important both for planning resource investments and for discovering areas where we can improve clinical management. One major gap in our knowledge is how direct healthcare spending and utilization change as the disease progresses -- starting at pre-clinical stages; thus current data on dementia-associated healthcare burdens may underestimate true costs and may not fully address management issues. However, existing studies rely on data with limited ability to examine costs across the ful spectrum of cognitive decline. We propose to address the knowledge and data gaps by applying Dartmouth's expertise in Medicare claims- based healthcare research to the epidemiologic resources and expertise of the Nurses' Health Study, an ongoing cohort that began in 1976, with 121,700 women age 30-55 years. The long-term goal is to use the rich longitudinal data on risk factors and cognitive measures in the Nurses' Health Study (NHS) for a larger study of the trajectory of healthcare spending related to cognitive decline by linking to Medicare administrative data. The NHS performed cognitive batteries every 2 years over 6-8 years, starting in 2000, on nearly 20,000 older women across the United States, which can provide the cognitive measures lacking in the claims data. Linking these data sources will yield a powerful resource for research; in addition to its much strength, the NHS is a large and geographically diverse sample, allowing detailed examination of healthcare costs and utilization by region and by other variables, such as co-morbidities. A limitation of the NHS is it includes nurses whose professional/educational attainment could lead to altered use of health care services and non-generalizable conclusions. Thus, this R21 is designed to: (1) establish the linkage between the NHS and CMS databases; (2) address the methodological concern that nurses have different utilization and spending patterns from the general population through comparison with the general Medicare population; and (3) generate initial data regarding the relationship between the spectrum of cognitive decline and healthcare use and costs (calibrated for any differences between these nurses and the general population). Specifically, after linkage of the NHS to Medicare claims data, this study will compare utilization among NHS participants versus the general Medicare population, and then begin to explore how level of cognitive decline (including the spectrum from no decline to cognitive impairment to dementia) relates to costs and utilization. With greater understanding of healthcare utilization patterns in NHS, this R21 will form the basis for future collaborative research between Dartmouth and NHS, leveraging one of the longest running epidemiologic research studies to inform new areas of health economic and services research, and potentially many other questions regarding mid-life risk factors and late life healthcare use.