Residential green spaces and risk of cardiovascular diseases

Relation

Yeager, R., Riggs, D., DeJarnett, N., et al. Association between residential greenery and risk of cardiovascular disease.J Am Heart Assoc. 2018;7(e009117).

Study objective

Assessing the Effects of Residential Green Spaces on Markers of Cardiovascular Disease (CVD)

Design & participants

This was a cross-sectional study of 408 participants (48% female, mean age 51.4 ± 10.8 years) who were patients at the University of Louisville Outpatient Cardiovascular Clinic between 2009 and 2014. All participants were recruited based on mild to moderate cardiovascular risk factors (e.g. mean BMI 32.9, mean blood pressure 131/80) and/or history of previous cardiac events.

Target parameters

Participants' home addresses were mapped using Geographic Information System (GIS) software and spatially correlated with current Normalized Difference Vegetation Index (NDVI) satellite data to assess the relative amount of surrounding green space in 250 m and 1 km radius circles using a standardized method from −0.1 (completely urban/no vegetation) to 0.9 (dense forests).

Urine and blood biomarker data were collected from each participant to assess current cardiovascular risk, damage and/or repair as follows:

• Kardiovaskuläres Risiko: Adrenalin-, Noradrenalin-, Dopamin-, Serotonin-, Normetanephrin-, 3-Methoxytyramin-, Metanephrin-, 5-Hydroxyindol-3-Essigsäure-, Homovanillinsäure- und Vanillylmandelsäurekonzentrationen im Urin, alles Marker der sympathischen neuroendokrinen Aktivierung, von denen bekannt ist, dass sie zu kardiovaskulären Erkrankungen beitragen.
• Herz-Kreislauf-Schäden: F2-Isoprostan im Urin, ein Marker für oxidativen Stress.
• Herz-Kreislauf-Reparatur: Untertypen 1-15 der Serum zirkulierenden angiogenen Zellen (CAC), die das erneute Wachstum der Gefäße nach einer Schädigung widerspiegeln.

All samples were collected between 1:00 and 4:00 p.m. to minimize circadian fluctuations. Urine samples were standardized for creatinine levels.

Patient biomarker and NDVI data were analyzed using GIS spatial correlation software. All results were adjusted for multiple demographic, clinical, residential and environmental factors, including age, gender, ethnicity, smoking status, BMI, statin use, median household income, area deprivation index, road density within 50 m of residence and concentration of PM2.5 (fine particulate matter with a diameter <2.5 micrometers) air pollution outside the home for all statistical purposes Models.

Key insights

After adjusting for all measured factors listed above, the data shows a significant inverse association of residential green space with all biomarker categories, including the following:

• Abnahme der Epinephrinkonzentration im Urin mit zunehmender Wohnbegrünung (−6,9 % pro Δ 0,1 NDVI; 95 % KI: −11,5 % bis −2,0 %, P=0,006) innerhalb von 250 m, mit statistischer Signifikanz bei 1 km.
• Abnahme der F2-Isoprostan-Konzentration im Urin mit zunehmender Wohnbegrünung (−9,0 % pro Δ 0,1 NDVI; 95 % KI: −15,1 % bis −2,5 %, P=0,007) bei 250 m, mit statistischer Signifikanz bei 1 km.
• Abnahme relevanter CAC-Konzentrationen im Serum mit zunehmender Wohngrünfläche innerhalb von 250 m (Effektstärken zwischen –8,0 % und –15,6 %) und 1 km (Effektstärken zwischen –6,9 % und –10,1 %).

The data showed even more pronounced associations for certain groups, including women, participants who were not taking beta-blockers, and participants without a history of previous myocardial infarction.

Practice implications

This study is published inJournal of the American Heart Associationand demonstrates the increasing interest of the conventional medical system in the United States in issues of nature and health. Disciplines such as urban planning, public health and parks and recreation have been researching the beneficial effects of green spaces for many years. It's nice to see more medical journals taking an interest in this topic.

The results of the current study, currently under review, should come as no surprise. Empirical studies have reported positive effects of exposure to green spaces for many decades.¹One of the first of these studies, published inThe lancetmore than a decade ago showed a significant reduction in cardiovascular mortality among people living in areas surrounded by larger green spaces, using the entire British National Health Service data set of 41 million people.²Other studies have shown similar associations of green spaces with coronary heart disease and stroke.^3.4

As suggested by the biomarkers used in this study, the proposed primary mechanism of action is modulation of the psychophysiological stress response with resulting effects on physical and mental health. This is sometimes referred to as “allostatic load.”^5.6Much recent research has demonstrated the relationship between neighborhood environmental factors and increases in allostatic load.^7.8and decades of research have explored the effectacuteExposure to green spaces on biomarkers of stress.⁹This current study is one of the first to use neuroendocrine and vascular repair biomarkers in a residential green space study, expanding the evidence for a mechanism of action of the above-mentioned epidemiological cardiovascular outcomes based on the reduction of psychophysiological stress and allostatic load.

restrictions

As a cross-sectional study, the data here can only show associations between residential green spaces and CVD biomarkers. It cannot establish causality, and because participants were not asked how much time they spent where they lived, it may not accurately reflect how length of exposure to green spaces influences these biomarker results.

Of greater interest is why epinephrine is the only urinary neuroendocrine biomarker (of the 10 tested) that showed an association. If residential green space has an impact on psychophysiological functioning, as other studies have reported, why do these other biomarkers not reflect these changes? It may be that fluctuations in these markers are too transient to measure baseline effects of chronic home exposures, in which case other markers such as cortisol may be more appropriate. Other studies have examined this approach with positive results.¹⁰

This study is published inJournal of the American Heart Associationand demonstrates the increasing interest of the conventional medical system in the United States in issues of nature and health.

Furthermore, it is interesting that a study measuring cardiovascular risk did not use more conventional cardiovascular biomarkers such as high-sensitivity C-reactive protein (hs-CRP) or fibrinogen, when such markers are known to respond to psychophysiological stress. All risk biomarkers in this study were collected via a urine sample, but blood was collected from each participant to assess vascular repair capacity via CAC counting, allowing collection of hs-CRP or fibrinogen. It may be that these latter markers reflect inflammatory immunological activity rather than neuroendocrine stress. Regardless, future studies may wish to expand their collection of different biomarkers to enable more robust investigation of potential mechanisms.

Conclusions

Cardiovascular diseases remain a major cause of morbidity and mortality. There is evidence that environmental factors such as proximity and exposure to recreational green spaces influence stimulatory, oxidative and repair mechanisms that impact cardiovascular health. It may be clinically and economically beneficial to support the maintenance and access of these green spaces as part of a holistic, preventative approach to reducing the burden of disease.