Interactions between multiple environmental factors and associations with generalized anxiety disorder in Nurses’ Health Study II

Abstract

Background and Aim: Built and natural environments are linked to lower anxiety. Results are mixed due to heterogeneous study populations and definitions of anxiety. We longitudinally examined associations between generalized anxiety disorder (GAD) symptoms and exposure to residential greenness, walkability, and neighborhood socioeconomic status (nSES) and their interactions in the Nurses’ Health Study II. Methods: 79,838 participants completed the 7-item GAD Assessment (GAD-7) in 2013 and/or 2017. GAD-7 scores for both time points were dichotomized at a clinically-relevant cutoff (GAD-7 ≥ 5), indicating at least mild anxiety symptoms. Annual average and peak (July) greenness were assigned to residential addresses using Landsat-based Normalized Difference Vegetation Index (NDVI) at 270m and 1230m buffers. Walkability was calculated from summed z-scores of 2010 Census population density, Tiger/Line shapefile road intersection density, and Infogroup business density. nSES z-scores were linked using 2010 Census data. We employed generalized estimating equations (GEE) for individual and joint exposure models to estimate odds ratios (OR) and 95% confidence intervals (95% CI) adjusted for sociodemographic and lifestyle risk factors for anxiety. Results: Interquartile range increases in peak 270m NDVI (OR: 0.98, 95% CI: 0.96, 1.00), peak 1230m NDVI (OR: 0.97, 95% CI: 0.95, 1.00), and nSES z-score (OR: 0.97 95% CI: 0.95, 0.99) were protective. Higher walkability (OR: 1.02, 95% CI: 1.01, 1.03) was associated with elevated odds of anxiety symptoms. Interaction models showed substantial heterogeneity. For example, peak 270m NDVI was more protective in lower nSES areas (lowest quintile OR: 0.94, 95% CI: 0.90, 0.98, highest quintile OR: 1.01, 95% CI: 0.96, 1.06). The adverse association observed with walkability was stronger in higher NDVI areas. Conclusion: Higher residential NDVI and nSES and lower walkability were associated with decreased odds of anxiety symptoms. Interactions between these contextual factors identified subpopulations that could benefit from improved residential built and natural environments.