Abstract Body (Do not enter title and authors here): Introduction: Healthy urban environments are essential for improving cardiovascular health. Although exposure to wild green surroundings has been shown to have positive effects on mental and physical health, the effect of urban greenspaces on cardiovascular function and stress remain unclear.
Research Question: Does being in an urban park decrease stress and autonomic tone as reflected by heart rate variability (HRV).
Methods: We invited healthy adults (n=41; age 25-70 years) to participate in a cross-over panel study. They were randomly assigned to start in either a typical urban park or an adjacent urban space, spending 20min sitting and 20min walking. Self-reported distress and State-Trait Anxiety Index (STAI) scales were assessed before and after exposure. Paired t-test was used to compare stress levels by site, and the effect size was calculated using regression analysis after adjusting for the level of starting distress. ECG recordings were acquired for the duration of the visit. HRV epochs of 5 min at the end of sitting or walking period and 40 min for the entire study were analyzed and compared using paired t-test.
Results: Pre-exposure distress and STAI summed scores were similar for the park and built spaces, but the level of distress was lower after visiting the park compared with built space (19.6±15.0 vs. 24.1±12.1; p=0.05). STAI scores were decreased after visiting the park, but not the built space (-5.4±8.2 vs. 0.8±6.8; p=0.003). When adjusted for the starting levels of distress, the summed STAI score after visiting the park was reduced by 6 (-10.34, -2.11), but no change for the built site. The standard deviation of NN intervals (SDNN) was higher in the park than the urban site (41.7 vs. 37.3; p=0.03) and the HR was lower (78 vs. 81; p=0.01) across the entire study epoch (40min). There was no significant change during the seated portion of visits, but across the walking portion, the values of SDNN were higher in greenspace (32.2 vs. 27.0; p= 0.01) and HR was lower (87 vs 84; p=0.02). Other HRV indices were not significantly affected.
Conclusion: Visiting an urban park, but not a built environment, led to a decrease in self-reported distress, and a relative shift in the autonomic nervous system towards parasympathetic dominance. Although the relationship between changes in stress and HRV remain unclear, access to greenspaces may be an important factor in maintaining and enhancing cardiovascular health in urban environments.