Accurate and valid measurement of cognitive and functional decline for the detection of Alzheimer’s Disease and Related Dementias (AD/ADRD) in Latino/a/x older adults is a critical public health priority. The Latinx population is rapidly growing and aging in the U.S. with enormous expected growth of AD/ADRD in older Latinx adults in the coming years. It is unknown whether cognitive assessment instruments measure cognitive health with equal precision and validity across Latinx and non-Latinx white (NLW) older adults, which is a critical barrier to the accurate detection of AD/ADRD, its determinants, and its impact. This study will use a mixed-methods approach to evaluate the validity and equivalence of measures of cognitive and functional decline in Latinx and NLW older adults, using the Harmonized Cognitive Assessment Protocol (HCAP) cognitive test battery (HCAP-R) and informant ratings of cognitive and functional decline (HCAP-I). Specific Aim 1 will examine the extent to which the HCAP-R and HCAP-I exhibit statistical evidence of measurement bias across years of education, assessment language (English/Spanish), and ethnicity (Latinx/NLW), using a series of psychometric analyses. Data from the Health and Retirement Study (HRS)-HCAP study will be combined with data from the Brain Attack Surveillance in Corpus Christi (BASIC)-Cognitive study for this analysis. Specific Aim 2 will utilize longitudinal data from the BASIC-Cognitive study to examine whether the HCAP-R is equally predictive of longitudinal trajectories of informant-rated cognitive and functional decline (HCAP-I) between Latinx and NLW older adults and whether adjustment for statistical measurement bias eliminates any differences in this predictive equivalence. Specific Aim 3 will perform new data collection using a qualitative methodology (cognitive interviewing) to examine the linguistic and cultural validity of HCAP-R and HCAP-I items in a sample of Mexican American older adults with varying levels of education and Spanish language use. These data will provide a novel integration of mixed methods (psychometric, longitudinal prediction of cognitive and functional decline, and qualitative) to inform the equivalence and validity of the HCAP across culturally, linguistically, and educationally diverse older adults. This K23 program will provide PI Dr. Briceño with training to develop expertise in psychometric and longitudinal data analysis, qualitative research, population-based cognitive aging and health disparities research, and research leadership. Training will occur through individual mentoring, formal workshops and seminars, and international conferences. The K23 mentors are international leaders in Latinx brain health equity, psychometrics, population-based cognitive aging, and cross-cultural neuropsychological assessment of AD/ADRD. The K23 will provide Dr. Briceño with expertise and preliminary data to submit an R01 and to become an independent researcher in cognitive health di...