Mare Lohmus. The health effects of dense cities and the role of urban greening.

The health effects of dense cities and the role of urban greening Mare LĂľhmus mare.lohmus.sundstrom@ki.se

Cities – the predominant engine of innovation and wealth creation of societies • There is a strong positive correlation between the degree of urbanization of a country and its per capita income – if you double a city’s population, its economic productivity goes up by 130% • Resource sharing, greater opportunity for face-to-face interaction and more learning are the drivers of the higher productivity of cities

Cities – a source of pollution, crime and disease…

Current urban infrastructure and transport processes have been less than optimal and therefore creating problems with: • air pollution – worldwide about 3–4 million deaths/year • noise from rail and road transport – in Europe about 50,000 fatal heart attacks/, and 200,000 cases of cardio-vascular disease/year • sedentary behaviour – worldwide 2.1 million deaths/year • heat islands – could not find a number • lack of green space – no data available

Can we use greenness to counteract the health effects of urbanization?

Exposure to urban greenness has many positive health effects… … not only, but let’s leave it right now…

Improved pregnancy outcomes: Dzhambov AM, et al. Association between residential greenness and birth weight: Systematic review and meta-analysis.

Urban Forestry & Urban Greening. 2014;13(4):621-9

Take home message: Amount of green space in close proximity to the homes of pregnant women is positively associated with birth weight – evidence from Israel, USA, England, Germany Lithuania and‌ now also from Stockholm

Neighbourhood greenness and birth outcomes in a Swedish Birth Cohort Health & Place. 2019 • If the mother lives in an area with high level of greenness the odds of the baby being born underweight is lower • Residential area type is a significant effect modifier of the association between urban greenness and birth weight

Developmental effects: Dadvand P., et al. The association between lifelong greenspace exposure and 3-dimensional brain magnetic resonance imaging in Barcelona schoolchildren Environmental Health Perspectives. 2018;126(2)

Methods: Brain magnetic resonance imaging in 253 school children in Barcelona

Take home message: Higher exposure to urban greenness has a positive effect on brain development and is associated with better: • Concentration • Memory • Motoric development

Depression and mental health: Beyer KM, et al. Exposure to neighborhood green space and mental health: Evidence from the survey of the health of Wisconsin.

International journal of environmental research and public health. 2014; 11(3): 3453-72

Study group: Survey of the Health of Wisconsin (SHOW) database – 2479 individuals

Take home message: Green space lowers the levels of symptomology for depression, anxiety and stress

Reduced mortality: Villeneuve PJ, et al. A cohort study relating urban green space with mortality in Ontario, Canada.

Environmental research. 2012;115:51-8

Methods: 4 year cohort study of approximately 575,000 adults, 35 years and older, in urban Ontario, Canada; identified from income tax filings, and through record linkage to the Canadian Mortality Data Base.

Take home message: • Greenspace reduces nonaccidental mortality • The strongest association with respiratory disease mortality

Physical activity: Christian H, et al. A Longitudinal Analysis of the Influence of the Neighborhood Environment on Recreational Walking within the Neighborhood: Results from RESIDE. Environmental Health Perspectives. 2017;125(7):077009-1-10

Methods: During 8 years 1813 participants in Australia reported the frequency and total minutes of recreational walking/week within their neighborhood, and their neighborhood environment perceptions

Take home message: Local recreational walking activity is positively influenced by access to a medium-/large-size park, beach access, and higher street connectivity.

Other health effects?

Some evidence for: • Improved cardiovascular health factors • lower prevalence of diabetes and other metabolic health problems • lower prostate cancer incidence … but • more problems with hay fever … in greener neighborhoods

What about the methodology of these studies?

• Although being “very in” and extremely popular, health/urban greenness studies are quite a new research area.

Consequently, there are still many question marks…

Define urban greenness!

I can not‌ There is no universally accepted definition of urban greenness. It may include: a. places with natural surfaces/natural settings b. specific type of urban greenery: street trees, ornamental greenery c. urban parks d. private gardens e. roadside vegetation f. beaches

Define exposure • Most commonly it is only estimated based on the residential location Greenness around the residential address

Objective or subjective

Distance to the closest ”green area”

100 m 250 m

…Yes, I do wonder if that really is enough…

500 m

How is the exposure to green structure measured?

• • • •

Normalized Difference Vegetation Index (NDVI) Expresses the amount of photosynthesizing vegetation Estimated from satellite images (GIS) -1 < NVDI > +1

House

How is the exposure to green structure measured? â&#x20AC;˘ Proportion of surface covered with certain type of vegetation â&#x20AC;˘ Satellite images, aerial photographs, land use maps

How is the exposure to green structure measured?

• Distance from the residential address to the nearest "green area“ • Satellite images, aerial photographs, land use maps • You have to define what "green area" is…

Why do I prefer NDVI to land use maps â&#x20AC;˘ NDVI catches everything that is green â&#x20AC;˘ Land use maps often ignore street trees and do not show what is in private gardens

Scientific Reports | 5:11610 | DOI: 10.1038/srep11610

Scientific Reports | 5:11610 | DOI: 10.1038/srep11610

NDVI varies from year to year • Even true values vary for natural reasons • Clouds • Bad pictures, technical problems in image production, transmission, interpretation etc.

2004 & 2006

But is it really the effect of greenness that we measure? â&#x20AC;˘ It is very common globally that the level of residential greenness is strongly associated with socioeconomic status â&#x20AC;˘ You may adjust for it in the modelsâ&#x20AC;Ś but is it really enough to avoid residual confounding?

Stockholm is a tricky city…

• In urban municipalities the association between income and NDVI is negative (higher income is associated with less greenness) • In suburban municipalities the association is positive (higher income is associated with more greenness) • … But… if you are rich you can compensate…

Persson et al 2018. Landscape and Urban Planning 179 (2018) 103–106

Area type 2nd percentile Suburban Urban 3rd percentile Suburban Urban 5th percentile Suburban Urban 70th percentile Suburban Urban 95th percentile Suburban Urban

β (g)

95 % p-value 95 % CI

Stockholm is a tricky city…

The association between one IQR increase in 61; 492 maternal NDVI exposure and birthweight of “small” and “large” new-borns by using an -416; 332 adjusted quantile regression model stratified by area type 50; 360 -323;200

276 -42

0.012 0.826

205 -62

0.009 0.643

153 -66

0.015 0.430

30; 277 -230; 98

10 -157

0.830 0.001

-78; 97 -251; -59

99 -47

0.308 0.730

-91; 288 -313; 219

Why the difference between urban and suburban?

• Almost no individuals in the urban population were exposed to above median levels of residential greenness… so this group is “missing” • The lowest income quartile group was missing in the urban municipality • Highest income group was missing in the suburban municipality • Significantly higher number of mothers had post-high school education in urban area than in suburban ones • Urban population may to a higher degree compensate their lack of residential greenness by travelling or owning/visiting summerhouses

If the greenness effect is real, what are the mechanismsâ&#x20AC;Ś Markevych I, et al. Exploring pathways linking greenspace to health: Theoretical and methodological guidance.

Environmental research.

2017;158:301-17.

Markevych I, et al. Exploring pathways linking greenspace to health: Theoretical and methodological guidance. Environmental research. 2017;158:301-17.

Markevych I, et al. Exploring pathways linking greenspace to health: Theoretical and methodological guidance. Environmental research. 2017;158:301-17.

 Suggestion – vegetation may remove air pollutants  Empirical evidence – some but inconsistent

Markevych I, et al. Exploring pathways linking greenspace to health: Theoretical and methodological guidance. Environmental research. 2017;158:301-17.  Suggestion – vegetation reduces heat exposure  Empirical evidence – good  Empirical evidence of human health effects – several studies showing that heat-related mortality is lowest in the greenest areas

Markevych I, et al. Exploring pathways linking greenspace to health: Theoretical and methodological guidance. Environmental research. 2017;158:301-17.  Suggestion – vegetation reduces exposure to noise  Empirical evidence – a) Physical reduction – a little b) Psychological reduction – a bit more

Markevych I, et al. Exploring pathways linking greenspace to health: Theoretical and methodological guidance. Environmental research. 2017;158:301-17.

 Suggestion – vegetation encourages physical activity  Empirical evidence – many studies, mixed finding but…!!!

Markevych I, et al. Exploring pathways linking greenspace to health: Theoretical and methodological guidance. Environmental research. 2017;158:301-17.

 Suggestion – vegetation facilitates social cohesion  Empirical evidence – some evidence for children and elderly

Markevych I, et al. Exploring pathways linking greenspace to health: Theoretical and methodological guidance. Environmental research. 2017;158:301-17.

Relaxation, restoration, stress reduction

Decreased (normalized) cortisol secretion

Endocrine, cardiovascular, immunological and metabolic effects

Markevych I, et al. Exploring pathways linking greenspace to health: Theoretical and methodological guidance. Environmental research. 2017;158:301-17.

Relaxation, restoration, stress reduction

Decreased (normalized) cortisol secretion

Endocrine, cardiovascular, immunological and metabolic effects

Evidence for stress reduction • Some, but the methodology used is not always the best…

• Salivary cortisol – difficult with individual and diurnal variations

https://www.quora.com/Why-is-there-an-evening-rise-of-temperature-in-cases-of-tuberculosis

https://peerj.com/articles/2061/

Gidlow CJ et al. Natural environments and chronic stress measured by hair cortisol.

Landscape and Urban Planning. 2016;148:61-7 Methods: Exposure: Generalised Land Use Database, Index of Multiple Deprivation Outcome: Hair cortisol concentration Hair samples (3 cm) were collected from 132 healthy employed adults from UK reflecting past three months of cortisol secretion

Take home message: chronic stress is higher in areas with less natural environment

Aspinall P et al. The urban brain: analyzing outdoor physical activity with mobile EEG (electroencephalography device). Br J Sports Med. 2015;49(4):272-6.

Methods: 12 participants walked 25 min through three different areas of Edinburgh (urban shopping street, path through green space, and street in a busy commercial district). The equipment provided recordings labelled short- and, frustration, engagement, long-term excitement and meditation.

Take home message: Walking in the green space lowers frustration, engagement and arousal, and increases meditation.

Egorov AI, et al. Vegetated land cover near residence is associated with reduced allostatic load and improved biomarkers of neuroendocrine, metabolic and immune functions. Environmental research. 2017;158:508-21 Exposure: Land cover data Outcome: Allostatic load Cross-sectional, 206 adults, saliva and blood samples

Allostatic load â&#x20AC;&#x201C; biomarker-based measure of dysregulation reflecting the physiological consequences of stress (hormonal, immunological, neural)

Egorov AI, et al. Vegetated land cover near residence is associated with reduced allostatic load and improved biomarkers of neuroendocrine, metabolic and immune functions. Environmental research. 2017;158:508-21

Findings: An interquartile range increase in vegetated land cover was associated with 37 % reduced allostatic load.

Allostatic load

Allostatic load

But…

Environmental stressor

Increased cortisol secretion

Endocrine, cardiovascular, immunological and metabolic effects

• Many studies lack data for noise and air pollution…

• If these are not investigated as potential confounders or mediators we can not decide whether the health effect is due to greenness exposure or simply to absence of pollution

From a public health point of view, we want people to enjoy being outdoors...

Change the environment so people are more outdoors

There is nothing to suit everyone...

Depends on: • Our subjective perception of the environment (attractive?, clean?, secure?)

• Personal taste/Cultural preferences • If our needs are met (hobbies, health) And these differ between individuals due to: • Latitude and nature-type at the place of origin/residence • Socio-economic factors • Age • Sex

Thank you!