==== Front Innov Aging Innov Aging innovateage Innovation in Aging 2399-5300 Oxford University Press US 10.1093/geroni/igaa057.205 igaa057.205 Abstracts Session 2853 (Poster) Cognition and Cognitive Assessment AcademicSubjects/SOC02600 How Does Neighborhood Environment Influence Dementia Onset?: Evidence From the National Health and Aging Trends Study Wang Yi 1 Qin Weidi 2 1 University of Iowa, Iowa City, Iowa, United States 2 Case Western Reserve University, Cleveland, Ohio, United States 2020 16 12 2020 16 12 2020 4 Suppl 1 Program Abstracts from The GSA 2020 Annual Scientific Meeting “Turning 75: Why Age Matters”63 63 © The Author(s) 2020. Published by Oxford University Press on behalf of The Gerontological Society of America.2020This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.Abstract Existing research has established significant associations between older individuals’ social participation (e.g., visiting friends and family, going out for enjoyment, etc.) and their risk of developing dementia. However, little was known about the role of neighborhood environment (i.e., neighborhood social cohesion, neighborhood physical disorder). This study aims to investigate the moderating effects of neighborhood environment on the relationship between social participation and dementia incidence using data obtained from 8 waves (Rounds 1 through 8) of the National Aging and Trends Study. 7,416 Medicare beneficiaries aged 65 or above who were community-dwelling and free from dementia at Round 1 (2011) were selected. Among them, 1,005 participants developed dementia in the followed-up years from 2012 to 2018. We conducted survival analysis using the accelerated failure time (AFT) models to examine the moderating effects of neighborhood social cohesion and neighborhood physical disorder on the onset of dementia. The unit of time-to-event data was in years. Findings showed that the interaction term of neighborhood physical disorder and individual social participation was significant, indicating neighborhood physical disorder moderates the protective effects of social participation on dementia incidence. Specifically, among older adults who participate in social activities at the same level, the progression to the onset of dementia is 1.06 times faster for those living in neighborhoods with higher level (i.e., one unit increase in the score) of physical disorder. The findings recommend modification of physical environment at the neighborhood level to facilitate social participation for the betterment of cognitive health in later life.