Study links air pollution to higher risk of stroke and related death

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According to a long-term study, air pollution increases the risk of having a first stroke, additional strokes and death. Fairfax/Getty Images Media Archive
  • A new study has tracked the effect of air pollution on the risk of having a first stroke and dying from cardiovascular problems.
  • The researchers tracked the medical records of a large number of people and their exposure to air pollutants.
  • The study focuses on PM 2.5 pollution, tiny air particles that are dangerous to human health.

New research from the School of Public Health at Sun Yat-sen University in Guangzhou, China amplifies how air pollution could affect the trajectory of health from stroke to subsequent death.

The study, recently published in Neurology, focusing on the health impacts of PM 2.5 pellets. This fine particulate matter (PM) is harmful to human health and has a diameter of less than 2.5 microns, about 30 times smaller than a single human hair.

The researchers also looked at the levels of nitrogen dioxide (NO₂) and nitrogen oxides (NO𝑥) in the polluted air and measured the levels of air pollutants based on their weight in micrograms – 1 millionth of a gram. – per cubic meter of air, expressed in μg/m3.

The study shows that for each increase in PM 2.5 of 5 μg/m3, the risk of a first stroke increased by 24% and the risk of a first fatal stroke increased by 30%.

Each 5 μg/m3 increase in NO₂ and NO𝑥 was associated with a low risk of first stroke — 0.2% and 0.1%, respectively.

The pollutants also caused a slight increase in the risk of cardiovascular mortality in people who had already suffered a stroke. This was especially true for NO₂, which increased mortality risk by 0.04%, although this effect waned over time.

Dr. Franco FolinoPh.D., a research cardiologist in the department of cardiac, thoracic and vascular sciences at the University of Padua in Italy, not involved in the study, said Medical News Today:

“Despite the many studies that have shown the adverse health effects of pollution, there still seems to be little awareness about the need to take adequate measures to reduce exposure to pollutants, especially in the poorest populations. more at risk.”

“Just as climate change still fails to drive meaningful changes in environmental policy, the health effects of air pollution are vastly underestimated.”

– Dr. Franco Folino, Ph.D., research cardiologist

The observational study is based on an analysis of the health records of 318,752 people in the UKBiobank and several years of air pollution data from UKBiobank.

The researchers tracked the health progress of these people for 3,765,630 person-years of follow-up. During this period, 5,967 people suffered a first stroke or stroke. Additionally, 2,985 people experienced post-stroke cardiovascular effects and there were 1,020 subsequent deaths.

The researchers also used 1 year of air pollution data to estimate exposure based on where people lived. They modeled each individual’s exposure to pollutants based on data on land use, traffic, population and topography.

The data shows that people who had a stroke during the study had an average exposure of 10.03 µg/m3 of PM 2.5. For people without a stroke, the exposure was 9.97 µg/m3.

“This new study attempts to assess the ‘dynamic’ effects of pollution on stroke risk and mortality in a large population over a very long follow-up period,” Dr. Folino said.

“In essence, this is another demonstration of the long-term adverse effects of pollution, and in particular fine particulates and nitrogen oxides, on [the] cardiovascular system.”

Outside, PM 2.5 comes mainly from fossil fuel vehicles such as cars, trucks, buses, traditional trains, snowmobiles and construction equipment. Any process involving the burning of wood, oil, gasoline or coal can also contribute, including power plants.

Additionally, these small but dangerous particles can travel through the air, so natural events such as forest fires and volcanoes distribute them over long distances.

Inside the home, PM 2.5 can come from cigarettes, burning candles, cooking on a stove or in an oven, fireplaces, and space heaters that burn fuel.

“When we consider air pollution, we shouldn’t just think about the quality of the air we breathe outside. Very often the pollution can be higher at home,” said Dr. Folino, adding that people could also consume PM 2.5 in water and food.

“PM 2.5 seem particularly harmful because their small size allows them to penetrate deeper into the smallest bronchi, where they can induce inflammatory phenomena which seem largely responsible for the harmful effects of fine particles.

– Dr. Franco Folino, Ph.D., research cardiologist

Dr. Adi Iyera neurosurgeon at the Pacific Neuroscience Institute at Providence Saint John’s Health Center in Santa Monica, Calif., said DTM that PM 2.5 could lodge in the alveoli of the lungs. It could “cause a blockage of the blood oxygenation process which can lead to all sorts of other issues, from having low oxygen levels they can lead to pneumonia [or] respiratory infections,” he explained.

Dr Folino added that “a larger particle is more easily intercepted in the large airways, in the nose and in the trachea, and is then eliminated with the mucus”.

In the United States, websites like the federal government AirNow provide an assessment of the current local air quality. If you have an iPhone, you might be able to view a general air quality rating for your area in the Weather app.

On days when air quality reaches moderate to hazardous levels, the study authors suggest people should reduce outdoor activities, including exercise, and consider wearing masks and using purifiers of HEPA air.

“All people, but especially those at high cardiovascular risk, should avoid exposure to high levels of pollution,” Dr. Folino said. “We must practice physical activities in healthy areas and be careful of possible sources of pollution indoors. [the] residence.”

Of course, Dr. Iyer noted that people living in densely populated urban areas aren’t necessarily able to avoid air pollution.

“Take care of your health in other ways to make sure you have strong lungs by exercising, staying physically fit, eating a good diet, and not smoking. These are all things for mitigate and compensate exposure to particles, air pollution.

– Dr. Adi Iyer, neurosurgeon

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