Modification of Heat-Related Mortality in an Elderly Urban Population by Vegetation (Urban Green) and Proximity to Water (Urban Blue): Evidence from Lisbon, Portugal

Abstract

Background:Urban populations are highly vulnerable to the adverse effects of heat, with heat-related mortality showing intra-urban variations that are likely due to differences in urban characteristics and socioeconomic status.Objectives:We investigated the influence of urban green and urban blue, that is, urban vegetation and water bodies, on heat-related excess mortality in the elderly > 65 years old in Lisbon, Portugal, between 1998 and 2008.Methods:We used remotely sensed data and geographic information to determine the amount of urban vegetation and the distance to bodies of water (the Atlantic Ocean and the Tagus Estuary). Poisson generalized additive models were fitted, allowing for the interaction between equivalent temperature [universal thermal climate index (UTCI)] and quartiles of urban greenness [classified using the Normalized Difference Vegetation Index (NDVI)] and proximity to water (≤ 4 km vs. > 4 km), while adjusting for potential confounders.Results:The association between mortality and a 1°C increase in UTCI above the 99th percentile (24.8°C) was stronger for areas in the lowest NDVI quartile (14.7% higher; 95% CI: 1.9, 17.5%) than for areas in the highest quartile (3.0%; 95% CI: 2.0, 4.0%). In areas > 4 km from water, a 1°C increase in UTCI above the 99th percentile was associated with a 7.1% increase in mortality (95% CI: 6.2, 8.1%), whereas in areas ≤ 4 km from water, the estimated increase in mortality was only 2.1% (95% CI: 1.2, 3.0%).Conclusions:Urban green and blue appeared to have a mitigating effect on heat-related mortality in the elderly population in Lisbon. Increasing the amount of vegetation may be a good strategy to counteract the adverse effects of heat in urban areas. Our findings also suggest potential benefits of urban blue that may be present several kilometers from a body of water.Citation:Burkart K, Meier F, Schneider A, Breitner S, Canário P, Alcoforado MJ, Scherer D, Endlicher W. 2016. Modification of heat-related mortality in an elderly urban population by vegetation (urban green) and proximity to water (urban blue): evidence from Lisbon, Portugal. Environ Health Perspect 124:927–934; http://dx.doi.org/10.1289/ehp.1409529

A Review of Epidemiologic Studies on Greenness and Health: Updated Literature Through 2017

“…Two studies sought to understand whether the relationship between heat and mortality was modified by greenness exposure and found that the association between temperature and mortality was attenuated in greener areas [54,55]. In Portugal, mortality was 14.7% (95% CI: 1.9, 17.5) higher comparing extremely hot days (> 99 th percentile of temperature) to other days in areas in the lowest greenness quartile (NDVI <0.23), but only 3.0% (95% CI: 2.0, 4.0) higher in areas in the highest NDVI quartile (>0.48) [55].…”

“…In Portugal, mortality was 14.7% (95% CI: 1.9, 17.5) higher comparing extremely hot days (> 99 th percentile of temperature) to other days in areas in the lowest greenness quartile (NDVI <0.23), but only 3.0% (95% CI: 2.0, 4.0) higher in areas in the highest NDVI quartile (>0.48) [55]. In Korea, mortality was 4.1% (95% CI: 2.3, 5.9) higher per 1 Celsius degree increase for days above the 90 percentile of temperature in areas in the lowest NDVI tertile (<0.341) but only 2.2% (−0.5, 5.0) higher in the highest NDVI tertile (>0.542) [54].…”

“…In addition, a study in Europe and another in Asia showed that greenness may attenuate associations between extreme heat and mortality [54,55]. While new large, prospective cohort studies from different countries added support that for greenness protecting against mortality, further research should investigate potential effect modification by gender, urbanicity, and SES.…”

The influence of socioeconomic, biogeophysical and built environment on old-age survival in a Southern European city

“…Urban residents are also generally exposed to poorer physical Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/healthplace environments than their rural counterparts (Burkart et al, 2015;Marzluff et al, 2008;Vlahov et al, 2007) high pollution levels, lack of natural greenspace, and frequent temperature extremes. All these influences have well-documented consequences for the health and survival of the populations (Burkart et al, 2015;Hajat et al, 2007;Shumake et al, 2013;Takano et al, 2002).…”

Urban Green Spaces and the Potential for Health Improvement and Environmental Justice in a Changing Climate

“…Urban trees and vegetation provide climate regulation services as they reduce the UHI effect through evapotranspiration and shading and can thus help preventing heatrelated morbidity and mortality (Chen et al 2014). Also urban blue spaces can decrease heat levels and mitigate heat-related morbidity (Burkart et al 2015). In this context, green and blue spaces may therefore be considered as examples of NBS.…”