Exploring associations of neighbourhood greenery, tree canopy, air pollution and walkability with cardiometabolic disease-related hospital admissions at midlife and beyond

Aim To examine associations of neighbourhood greenery, tree canopy, traffic-related air pollution and walkability with cardiometabolic disease among adults (≥45 years) admitted to hospital in the Frankston-Mornington Peninsula region, Australia. Few multi-exposure studies on this topic exist. Methods Our cross-sectional study assessed mean annual neighbourhood greenery using the Normalised Difference Vegetation Index (NDVI); tree canopy (% area); traffic-related air pollution (PM 2.5 ; NO 2 ) using land-use regression models, and walkability using Walk Score®. Hospital admissions (in 2021) among patients with type-2 diabetes (T2D) or cardiovascular disease (CVD) were identified using ICD-10-AM admission codes in electronic health records data. Using multilevel logistic regression we examined associations between environmental exposures and odds of having T2D or CVD, adjusting for sociodemographic factors. Results Our sample comprised 14,378 admitted patients (mean age 65.8 (SD 12.7) years; 47% male), residing in 697 neighbourhoods with mean (SD) values: NDVI, 0.47 (0.09); tree canopy, 21.7 (13.2)%; PM 2.5 , 8.5 (0.6) μg/m 3 ; NO 2 , 5.2 (1.6) ppb. NDVI was associated with lower odds of having T2D, Odds Ratio (OR) = 0.39 [0.18, 0.82], as was tree canopy quintile OR = 0.95 [0.91,0.99]. PM 2.5 and NO 2 were associated with higher odds of T2D, OR = 1.26 [1.15,1.38] and OR = 1.06 [1.02,1.10], respectively; and with higher odds of CVD, OR = 1.10 [1.02,1.18] and OR = 1.03 [1.01,1.06], respectively. Walkability quintile was associated with higher odds of CVD, OR = 1.04 [1.01,1.08]. Conclusions Greenery and traffic-related air pollutants were associated with lower and higher odds, respectively of admitted patients having T2D or CVD. Further exploration with stronger, longitudinal study designs is required to inform public health policy/directions.