ABSTRACT There is emerging scientific evidence that modifiable risk factors for Alzheimer’s disease and related dementias (ADRD) can be traced back to early life. Development of brain regions such as the hippocampus and dendritic spine occur by age 2 years and dramatic neural development occurs through age 5 years. The effects of early childhood environments are thought to operate through multiple systems, including via negative in-utero conditions, which are thought to be impacted by parental resources, schooling, physical environment, and parental health behaviors like smoking and poor nutrition. However, because of the long time duration between exposure and outcome, there is little direct evidence on the magnitude and nature of these associations. Current evidence relies most heavily on retrospective measures of early environments, which are subject to recall bias, particularly when studying dementia. Moreover, various aspects of childhood environments are often difficult to untangle, and in fact, often conceived as one construct (i.e. childhood SES). There is thus a gap in knowledge regarding the specific mechanisms by which early-life factors may help to protect against later-life ADRD risk. The overarching goal of the parent R01, The long-term health effects of the New Deal: An 80 year follow-up of 4 cohorts (R01 AG059791), is to understand the extent to which long-term chronic disease outcomes are impacted by early life conditions by leveraging spatial variation in New Deal investments. The overall objective of this supplemental application is to advance the scientific understanding of early-life influence on ADRD risk through testing three specific types of early-life exposures: 1) increased area level parental employment, 2) additional educational resources, and 3) better nutritional environments. To accomplish our objective, we propose to use data on old-age cognitive function and/or dementia risk from four established, long term cohort studies. These data have already been (or are currently being) linked to the 1940 complete count census providing us with information on parental WPA participation and early life exact address which allows us to examine the impacts of specific New Deal programs on the long-term risk of ADRD. Our central hypothesis is that benefits from New Deal programs will be associated with lower levels of ADRD risk for individuals whose communities had improved: 1) employment, 2) educational resources, and 3) nutritional environments. Our specific aims are, Aim 1: Test the effect of New Deal area level employment on later-life ADRD risk, Aim 2: Test the effect of New Deal local area level increased access to educational opportunities on later-life ADRD risk, Aim 3: Test the effect of New Deal area level improved nutritional environments on later-life ADRD risk. We will test all three of these specific aims in all four datasets, and combine effect estimates across datasets to increase our statistical power, as well a...