SUMMARY The prevalence of cognitive decline and Alzheimer’s Disease and Related Dementias (ADRD) is socially patterned, with populations of lower socioeconomic status being disproportionately burdened by these conditions. While there has been much research examining the contribution of education to cognitive decline and ADRD risk, comparably less research has focused on income as a risk factor for cognitive decline and ADRD. Even less research has examined the association of income over the lifecourse with these outcomes. This is because most cohorts with an explicit focus on aging and age- related outcomes recruit participants in mid or late life. In addition, the paucity of research may be due to indicators of material wealth, such as income, being difficult to correctly measure and track over time. The parent grant addresses this research gap by using an innovative data pooling method to create a synthetic cohort. The synthetic cohort combines data from eight different cohort studies that, together, span the lifecourse. However, the parent grant’s pooling method is yet to be validated with real-world data. Furthermore, much of the research examining income’s contribution to cognition has utilized self- reported income, which may be subject to inaccurate recall. In this diversity supplement, we will use Social Security Administration (SSA) income data that is linked to Health and Retirement Study (HRS) participants to validate the lifecourse income measures generated from the parent grant’s pooling method. The SSA data will provide us with valid and accurate adulthood to retirement income data for HRS participants, while the synthetic cohort will pool self-reported income data from the HRS (cohort with income data from mid to late life) and the National Longitudinal Survey of Youth (NLSY; cohort with income data earlier in life). Our specific aims are to: (1) Compare HRS participants’ actual and accurate income data from the SSA to self-reported income data pooled across NLSY and HRS to cover early adulthood to retirement ages, and (2) Examine the relationship of income trajectories from adulthood to retirement with cognition, dementia and all-cause mortality using HRS-SSA linked data and, separately, pooled income data from the NLSY and HRS. This project will be doubly informative: validation of the parent grant’s pooling method will inform future approaches to lifecourse research for ADRD as well as other disease areas; additionally, the outcome analysis will robustly examine the association of lifecourse income trajectories with ADRD. Moreover, this project will provide the applicant with training in social epidemiology, causal inference, and data pooling as these areas related to ADRD research, which will increase his research capability and enhance diversity in the field of aging research.