Environment/Climate Change
Do green spaces moderate the impact of extreme heat on daily walking behavior? A nationwide multilevel geospatial analysis in Japan Masamichi Hanazato* Yoko Matsuoka Hiroaki Yoshida Ichiro Kawachi SV Subramanian Yasuyuki Sawada Kazuki Matsumoto Katsunori Kondo
Aim
Physical activity levels, including daily steps counts, typically decline during extreme heat days, specifically among populations susceptible to heat stresses. However, it is less well understood whether built environment factors such as green spaces moderate the association between extreme heat and walking behavior.
Methods
We utilized smartphone data from a national sample in Japan. Daily data were obtained from 16,690 users aged 18 years or higher, from April 26 to October 25, 2023. Socio-demographic information of the users were obtained from survey responses either in November or December of 2022. We linked individual data with daily data on Wet Bulb Globe Temperature as well as geospatial data on residential green spaces (Normalized Difference Vegetation Index within a 500m network buffer). Extreme heat stress was defined as days of 28 degree Celsius or higher. We conducted multilevel mixed-effect linear regression analyses with cross-level interaction terms for heat stress, green space, and socio-demographics (age, gender, or income).
Results
Overall, the median value of participants’ average step counts during the period was 6143 (IQR: 4072 to 8731). Participants walked 244 fewer steps (95% CI: -274 to -214) on days with extreme heat compared to normal days. Additionally, regarding the two-way interaction term, older adults walked 199 steps less (-248 to -150) than younger adults on a day with extreme heat. According to the three-way interaction term, each 1-standard-deviation increase in residential green spaces was associated with 55 more steps (22 to 88) for women than men on a day with extreme heat. No clear association was observed for the low-income group.
Conclusion
Residential green spaces may buffer the adverse impacts of heat stress on walking, specifically for women.
