Abstract 032: Rural Versus Urban Living and Incident Cognitive Impairment in the Reasons for Geographic and Racial Differences in Stroke Study (REGARDS)

Abstract

Objective: To estimate the association of rural vs urban living in the United States (US) with incident cognitive impairment (ICI), and to assess confounding, mediation, and effect heterogeneity by demographic, social, behavioral, and clinical risk factors. Methods: REGARDS is a cohort of 30,239 adults aged 45+ in the 48 contiguous states. We analyzed 20,592 participants who at baseline (2003-2007) were cognitively intact with no history of stroke and had cognition assessed an average of 7.1 years later. We used Rural-Urban Commuting Area (RUCA) codes to classify participants as urban (n = 16,436), large city/town (n = 2,420), or small/isolated rural (n = 1,736) at baseline. We defined ICI as falling ≥1.5 SD below the mean on at least two of three cognitive tests administered during follow-up: word list learning, word list delayed recall, and animal naming. Using urban as the referent, we estimated odds ratios of ICI for rural and for large city/town. Results: ICI occurred in 1,291 participants (6.3%). Rural residents had 49% higher odds of ICI adjusted for confounding by demographics (Model 2 in Table, OR = 1.49 [95% CI: 1.19, 1.85]). After further adjusting for potential mediators (Models 3-6), odds of ICI remained 25% higher for rural vs urban (Model 6, OR = 1.25 [0.99, 1.56]). In assessing effect heterogeneity, we found synergism of rural dwelling with black race, physical inactivity, and low self-rated health (all P < 0.1; see ORs in Table), but not for other ICI risk factors. We found no difference in ICI for large city/town vs urban (demographics-adjusted OR = 1.08 [0.88, 1.33]; fully adjusted OR = 0.95 [0.77, 1.18]), and no effect heterogeneity of ICI risk factors by large city/town (all P > 0.2). Conclusion: Rural living is an important social determinant of cognitive health in the US. ICI was significantly more frequent among rural dwellers than urban dwellers, partly due to confounding or mediation by ICI risk factors. Odds of ICI were highest for rural dwelling combined with black race, physical inactivity, or low self-rated health.