Heart healthy cities: genetics loads the gun but the environment pulls the trigger

Abstract

The world's population is estimated to reach 10 billion by 2050 and 75% of this population will live in cities. Two-third of the European population already live in urban areas and this proportion continues to grow. Between 60% and 80% of the global energy use is consumed by urban areas, with 70% of the greenhouse gas emissions produced within urban areas. The World Health Organization states that city planning is now recognized as a critical part of a comprehensive solution to tackle adverse health outcomes. In the present review, we address non-communicable diseases with a focus on cardiovascular disease and the urbanization process in relation to environmental risk exposures including noise, air pollution, temperature, and outdoor light. The present review reports why heat islands develop in urban areas, and how greening of cities can improve public health, and address climate concerns, sustainability, and liveability. In addition, we discuss urban planning, transport interventions, and novel technologies to assess external environmental exposures, e.g. using digital technologies, to promote heart healthy cities in the future. Lastly, we highlight new paradigms of integrative thinking such as the exposome and planetary health, challenging the one-exposure-one-health-outcome association and expand our understanding of the totality of human environmental exposures.

Keywords: Air pollution; Environmental stressors; Heart healthy city; Heat islands effects; Light pollution; Noise pollution; Urban and transport planning and design interventions.

Graphical abstract

Figure 1

Global burden of disease and non-communicable disease. (A) The proportional distribution of global deaths attributable to communicable diseases, non-communicable diseases, and injuries for 1990, 2010, and projected for 2030. Graphs generated from previous data.  ^,   (B) Global World Health Organization status report on non-communicable diseases 2016 estimating the leading causes of death by different categories of non-communicable diseases. The category ‘Others’ comprises neurodegenerative and other neurological disease, musculoskeletal diseases, congenital anomalies, digestive disorders, endocrine/blood/immune disorders, genitourinary diseases, and other categories of orphan disease. CD, communicable disease; NCD, non-communicable disease; CVD, cardiovascular disease; RD, respiratory disease. Graphs generated from previous data.

Figure 2

Sources of air pollution in cities and contribution of sources to PM_2.5 air pollution. PM, particulate matter (e.g. PM_2.5 and PM₁₀ with a diameter of <2.5 or 10 µm); UFP, ultrafine particles (diameter usually <0.1 µm); BC, black carbon; SO₂, sulphur dioxide; NO_x, nitrogen oxides (e.g. nitric oxide, nitrogen dioxide). Adapted from previous report with permission.

Figure 3

Projections for population growth, urbanization, and their health impact. (A) Global population in the year 2010 and projections for 2050 according to four shared socioeconomic pathway (SSP) models, and percentages exposed to unhealthy levels of PM_2.5 (exceeding the World Health Organization guideline of 10 µg/m³), assuming that air pollution remains at the levels of 2010. (B) Global, annual premature mortality from the exposure to PM_2.5, assuming 2010 emissions and population developments according to four SPPs. The error bars indicate 95% confidence intervals. (C) Fractional change in urban population per country between 2010 and 2050 according to the ‘middle-of-the-road’ scenario SSP2. Graphs generated from data and using methods previously published.  ^,

Figure 4

Noise exposure of the population. Number of people exposed to various L_den noise bands based on areas covered by strategic noise maps in 2017, EEA-33 [L_den: noise level based on energy equivalent noise level (Leq) over a whole day with a penalty of 10 dB(A) for night time noise (23.00–7.00) and an additional penalty of 5 dB(A) for evening noise (i.e. 19.00–23.00)]. Graph generated from previous data with permission.

Figure 5

Co-localization of environmental pollutants. (A) Light pollution in the USA in the year 1997. Calculated according to Cinzano in ‘Light Pollution: The Global View’ (edited by H.E. Schwarz) and reused with permission by P. Cinzano, F. Falchi, C.D. Elvidge. VC 2001 ISTIL-Light Pollution Science and Technology Institute, Italy. Distribution of air pollution (B) and noise exposure levels (C) show a co-localization with light pollution in the USA. Air pollution map reused from previous data. © 2019 Khan et al. under the Creative Commons Attribution License. Noise pollution map was qualitatively approximated from United States Department of Transportation, Bureau of Transportation Statistics (https://maps.dot.gov/BTS/NationalTransportationNoiseMap/ (Date accessed 19 April 2021)). Red colour = areas with higher noise exposure. Orange colour = noise exposure hot spots. (D) Hazard ratio for light pollution-mediated cardiovascular mortality. High particulate matter caused additive risk effects for coronary heart disease death. Graph was generated from previous tabular data. (E) Hazard ratio for long-term air pollution-mediated cardiovascular mortality. Graph was generated from previous tabular data: upper three values, values 4–6 from top, and bottom value. (F) Hazard ratio for long-term noise pollution-mediated ischaemic heart disease. Graph was generated from previous tabular data. All tabular data used with permission. REF, reference value; CVD, cardiovascular disease; CEV, cerebrovascular; IHD, ischemic heart disease; HT, hypertension; HF, heart failure.

Figure 6

Modern city construction. (A) Illustration of the terms density, distance, and diversity as applied in the compact cities model. Redrawn from previous report with permission. (B) Traffic flows before and after the Superblock implementation in Barcelona. Reused from previous report with permission.