Urban Green Spaces and Tree Canopies may Help Prevent Cardiometabolic Diseases

by | Oct 8, 2020 | 2020, Cardiovascular Health, Diabetes

Written by Joyce Smith, BS. This study suggests that restoring local tree canopies in neighborhoods may help prevent the incidence of cardiometabolic diseases.

park benchesRecent studies have shown that type 2 diabetes can be prevented by living near parks, woodlands, and other nearby green spaces 1. Indirect evidence suggests that  green spaces can help prevent diabetes and other non-communicable diseases such as cardiovascular disease and hypertension in cities through countering  the impacts of  noise 2 and  air pollution 3 from air craft and  vehicle  traffic. Consequently, these factors interact with the age, occupation and socioeconomic circumstances of populations to affect them differently. Tree canopies offer a number of health benefits particularly for disadvantaged communities where air conditioning is nonexistent and the prevalence of underlying health conditions can increase vulnerability. Tree canopies may be beneficial in that they provide shade from the sun and prevent areas of intense heat.4 In particular, for high-density urban living environments where heat islands develop, the cooling of air and shading effect of trees encourage more outdoor activities 4, 5. A recent study by Astell-Burt and colleagues found an association between psychological benefits and the species richness of urban greenspaces where contact with nature provides opportunities for psychological restoration and stress reduction 6. They found that the greatest benefits occurred when more tree canopies and biodiversity existed to provide a variety of birdlife 7. An earlier studiy by the Astell- Burt team found an association between green spaces and sleep duration in Australia 8. Since then, many more studies from various countries have reported similar beneficial results.

In their most recent study, Astell-Burt and colleagues hypothesized that parks, woodlands and other nearby green spaces might help prevent cardiovascular disease. They assessed whether the previous results of tree canopy and green space health benefits could be applied to cardiovascular prevention.  Thus in a longitudinal cross-sectional study of three Australian cities, they linked total green space and tree canopy (as percentages of landcover within a 1 mile radius from residential homes) to a sample of 46,786 residentially stable participants in the Sax Institute’s 45 and Up Study (a 6-year study from 2006–09 with a follow-up from 2012–15). Using various models and after adjusting for confounders such as age, sex, income, education and employment and couple status, they investigated whether people with more green space and tree canopy had a lower odds of developing incident diabetes, hypertension, and CVD. People did not relocate during this time.

Their current study 9 found that a 1% increase in combined total green space and tree canopy was associated with decreased incidence of prevalent diabetes, hypertension and CVD. Areas that had a 1% increase in tree canopy, but not total green space, was associated with a decrease in incident diabetes, hypertension, and cardiovascular disease. Areas with 30% or more increase in tree canopy was associated with reduced risk of incident diabetes, hypertension and CVD; however, total green space was associated with lower odds of prevalent diabetes only.

An important study limitation is that most of this evidence comes from cross-sectional studies, thus giving us only “snapshots” of a point in time. Other potential sources of bias include healthier people moving to greener areas and the self-reporting of doctor-diagnosed diabetes, hypertension and cardiovascular diseases at baseline and follow-up.

This study validates the contribution of tree canopies to diabetes, hypertension and CVD prevention but future work is necessary as well to support the World Health Organization’s global directive that requires action and support from many sectors of society to prevent diabetes and other noncommunicable diseases 10. Future research should, in addition, provide evidence-based guidelines to urban planners and landscape architects to assist them in increasing our green spaces for all urban communities.

Source: Astell-Burt, Thomas, and Xiaoqi Feng. “Urban green space, tree canopy and prevention of cardiometabolic diseases: a multilevel longitudinal study of 46 786 Australians.” International journal of epidemiology 49, no. 3 (2020): 926-933.

©The Author(s) 2019. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/)

Click here to read the full text study.

Posted October 8, 2020.

Joyce Smith, BS, is a degreed laboratory technologist. She received her bachelor of arts with a major in Chemistry and a minor in Biology from  the University of Saskatchewan and her internship through the University of Saskatchewan College of Medicine and the Royal University Hospital in Saskatoon, Saskatchewan. She currently resides in Bloomingdale, IL.

References:

  1. Astell-Burt T, Feng X, Kolt GS. Is neighborhood green space associated with a lower risk of type 2 diabetes? Evidence from 267,072 Australians. Diabetes Care. 2014;37(1):197-201.
  2. Dzhambov AM. Long-term noise exposure and the risk for type 2 diabetes: a meta-analysis. Noise & health. 2015;17(74):23-33.
  3. Balti EV, Echouffo-Tcheugui JB, Yako YY, Kengne AP. Air pollution and risk of type 2 diabetes mellitus: a systematic review and meta-analysis. Diabetes Res Clin Pract. 2014;106(2):161-172.
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  7. Fuller RA, Irvine KN, Devine-Wright P, Warren PH, Gaston KJ. Psychological benefits of greenspace increase with biodiversity. Biology letters. 2007;3(4):390-394.
  8. Astell-Burt T, Feng X. Does sleep grow on trees? A longitudinal study to investigate potential prevention of insufficient sleep with different types of urban green space. SSM – population health. 2020;10:100497.
  9. Astell-Burt T, Feng X. Urban green space, tree canopy and prevention of cardiometabolic diseases: a multilevel longitudinal study of 46 786 Australians. Int J Epidemiol. 2020;49(3):926-933.
  10. Organization WH. Global Action Plan for the Prevention and Control of Noncommunicable Diseases 2013–2020. 2013; https://www.who.int/nmh/events/ncd_action_plan/en/.