PDS 70: Green space, Johan Friso Foyer, Floor 1, August 28, 2019, 1:30 PM - 3:00 PM
Background: Evidence is emerging that contact with urban green space has many positive health benefits, especially for stress reduction. However, few studies have measured the acute stress responses that occur from daily real-world urban green space exposures.
Methods: We used an experimental randomized crossover design to determine whether exposure to urban green space effects short-term stress responses. 24 participants walked a pre-determined 45 minute route that included 3 distinct green space exposure zones: 1) an urban park; 2) a tree-lined residential area; and 3) a busy commercial street. Short-term changes in stress responses were measured using a 32-channel mobile electroencephalogram (EEG) to track electrical activity in the brain and a non-invasive ambulatory blood pressure monitor to capture blood pressure and heart rate variability (HRV). We also measured continuous personal black carbon air pollution, noise and heat exposures. We analyzed differences by exposures zones using a repeated measures ANOVA.
Results: Both average HR and HRV were statistically significantly lower in the park compared to the busy urban area (average HR park=104.4, HRV=588.0; residential HR=105.4, HRV=580.8 and busy street HR=107.1, HRV=573.9, p<0.01). There was a statistically significant difference (p<0.05) in global theta values (decreases during stress), but not alpha values (increases during stress), between the park (theta=8.9, alpha=5.9); residential (theta=9.9, alpha=6.2) and in the busy street (theta=9.7, alpha=5.8). Average systolic (SBP) and diastolic blood pressure (DBP) was not statistically significantly different between the different exposure zones. Black carbon and noise levels differed significantly between zones but did not explain the differences observed in stress markers.
Conclusions: Green space reduces short-term stress markers, especially HRV and theta brain wave activity, in urban areas. These differences are not due to black carbon, noise or heat exposures.