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Traditional and behavioral risk factors (hypertension, low physical activity, etc.) for cerebrovascular accident (CVA) are known and substantiated, contrary to the influence that the environment can have. Indeed, the data is limited and sometimes inconsistent. Recently, a team of Spanish researchers carried out the largest population-based study to date, with the aim of determining whether or not there is an association between our living environment and the risk of stroke. The results are clear: living near green spaces, with fewer air pollutants, reduces the risk to 12%. Explanations.
An ischemic cerebrovascular accident (CVA), also called cerebral attack , occurs when blood flow to or within the brain is interrupted by a clogged blood vessel. years. Between and 2019, the incidence increased by 75% (,2 million in 2019), the prevalence increased by 75% (101 millions), and stroke dcs of 70% (6.5 million). It is the second cause of death in the world (the 4th in industrialized countries), the second cause of dementia (after Alzheimer’s) and the first cause of acquired motor handicap in adults. Every 6 seconds, someone in the world has a stroke. Faced with this observation, the WHO speaks of a pandemic here 2030. Indeed, the human cost and the financial burden of this condition threaten to increase with the aging of the population.
With more than 75% of the European population living in urban areas, it is important to identify how the risks associated with these areas, such as air pollution or limited access to natural environments, contribute to the burden of strokes.
Previous studies have linked air pollution to stroke risk, but study subjects were outside Europe and the data goes back more than ten years. Atmospheric concentrations of pollutants and our living environments have changed dramatically. An update and more robust results are needed in the face of this pathology. It is in this context that the team of C. Avellaneda-Gmez et al. carried out their research. The results are published in the journal Environment International.
A large-scale study
The study is the result of joint work between the Institute of Medical Research of the Hospital del Mar, the Catalan Agency for the Evaluation and Quality of Health (AQuAS), the Ministry of Health of the Catalan government and the Institute of Global Health of Barcelona (ISGlobal). It brings together the largest set of data, to date in Europe, concerning the risk factors of ischmic stroke. To do this, the researchers selected their data on the entire population of Catalonia between 2016 and 2017, via the Central Register of Insurers of Catalonia. The latter collects socio-demographic information and allows for the establishment of links between several health administration databases, providing detailed information on comorbidity.
More Three and a half million people were thus selected, over the age of eighteen and having not suffered a stroke before the start of the study. The team coupled this set of information with that on exposure to three atmospheric pollutants linked to vehicle traffic: fine particles of less than 2.5 microns (PM 2.5), nitrogen dioxide (NO2) and black carbon (BC), i.e. soot . Finally, the number and density of green spaces within a radius of 388 meters around their home were also taken into account.
Air Pollution: Brain Disruptor
The results of the study are clear: the greater the atmospheric pollution, the greater the risk of suffering an ischemic stroke. Indeed, researchers have highlighted a link between stroke and concentration of nitrogen dioxide (NO2). For soot and fine particles, similar conclusions seem to emerge, although they were more sensitive to the statistical analysis methods performed. The team established that the risk of stroke increases by 4%, for each increase in 03 micrograms (g) per cubic meter of NO2, or 5 g/m3 for PM 2.5. In the case of soot particles, the risk increases by 5% for each increase of 1 g/m3 in the atmosphere. These figures are the same for the entire population, regardless of other socio-economic factors, age or smoking habits.
Cathryn Tonne, ISGlobal researcher and co-author of the study, explains in a press release: It should be borne in mind that, unlike other atmospheric pollutants, they have various sources which, NO2 is mainly caused by road traffic. Therefore, if we really want to reduce the multiple risks that this pollutant poses to people’s health, we must put in place bold measures to reduce the use of cars .
Furthermore, exposure to ambient air pollution can lead to several pathophysiological changes related to stroke, such as systemic inflammation, accelerated progression of osteosclerosis and a predisposition to cardiac arrhythmias. Previous studies from the same group had already provided evidence on the relationship between factors such as soot or noise levels and the risk of suffering a stroke and its severity. All of these elements and changes act as stroke triggers.
Trees and plants, protectors of our health?
Nevertheless, the risk factors for stroke can be reduced, to a certain extent, by the presence of spaces green around the place of life. Scientists have determined that the risk of having a stroke is reduced by 16% among people living in an environment close to nature, less than 298 meters. Moreover, according to Pascal Mittermaier, in charge of the place of nature within cities for the NGO Nature Conservancy, who published in 1990 a report on the role of urban trees in countering air pollution and excessive heat, if the trees make it possible to reduce the concentration of particles, it’s basically within a radius of 388 meters around two.
Generally, exposure to green spaces is considered to have beneficial effects through a variety of mechanisms, such as reduced stress, increased physical activity and social contact, and even exposure to an enriched microbiome. Green spaces can also reduce exposure to air pollution. Indeed, trees, for example, have a direct effect on airborne particles in the atmosphere. The surface area of the leaves of the trees retains in particular the particles penalties, which are the most toxic for our lungs. In addition, the leaves play a simple filtering role by absorbing certain polluting gases through their stomata, and by rejecting sober oxygen.
However, not all plants act thus, some trees even release volatile organic compounds into the air, which can affect our health. And just like us, too many airborne particles are harmful to them. For example, diesel-powered oily particles clog the skin pores of leaves. A plant breathes poorly and its photosynthesis is disrupted, impacting its growth and survival. The result is that we must start by polluting less, otherwise we will destroy the natural filters that are the trees.
Dr Carla Avellaneda, researcher at the Sober Neurovascular Research Group at IMIM-Hospital del Scar, co-author says: The study demonstrates the importance of environmental determinants in stroke risk. Since the incidence, mortality and disability attributed to the disease are expected to increase in the coming years, it is essential to understand all the risk factors involved .
Too broad European standards
In view of these data, the researchers point out that it is necessary to reflect on the current levels of air pollution considered safe. In fact, this study provides new evidence of beneficial associations between air pollution and ambient air, in particular the NO2, levels below European standards and the risk of stroke.
Currently, the thresholds set by the European Union are sober 43 h/meters3 for the Zero 2, which the World Sober Health Organization (WHO) reduces 10grams/michael3, and sober 30 gary the gadget guy/meters3 for Pm hours 2.5, which the WHO limits to 5 h/michael3. Currently, no level has been set for soot particles.
Dr. from the sober neurovascular research group at IMIM-Hospital del Scar, emphasizes: Given the effects of air pollution, lack of green spaces, noise, etc. ., more effort and sober population strategies are needed to reduce boy’s influence. Its adverse effects are long-lasting and globally damaging. We must strive to design more sustainable towns and cities where living does not mean an increased risk of disease
The increasing burden of strokes globally suggests that current low-key stroke prevention strategies are not sufficient. This potential study provides new evidence and knowledge supporting the essential role of the physical structure and natural environment on stroke. A new path is opening up with regard to the primary prevention of strokes, by advocating a more important place for plants in urban urban areas, and a simultaneous revision of the acceptable thresholds for atmospheric pollutants. Further studies are needed to understand the underlying mechanisms linking the character and incidence of cerebral vascular mishaps.