科學家:空氣污染和動脈硬化有關 | 台灣環境資訊協會-環境資訊中心

科學家:空氣污染和動脈硬化有關

2013年05月03日
摘譯自2013年4月30日ENS美國,密西根州,安娜堡報導;姜唯編譯;蔡麗伶審校

日落時分,來自玉米加工設施的空氣污染。2012年2月攝於伊利諾伊州Summit鎮(圖片由David Zembower提供)。密西根大學學者和來自美國各地的共同研究人員指出,長期暴露於空氣污染和心臟病發作及中風有關,因為空氣污染會加速動脈硬化,又稱為動脈粥狀硬化。

密西根大學公共衛生學院流行病學助理教授Sara Adar和華盛頓大學環境和職業健康科學兼醫學教授Joel Kaufman帶領研究,4月底發表在醫學期刊「PLOS Medicine」。

Adar說,「研究結果幫助我們了解,空氣污染如何導致其他研究所觀察到的心臟病發作和中風風險增加。」

科學家們發現,空氣中的細懸浮微粒(PM2.5)濃度越高,頸動脈內部兩層增厚的速度越快。頸動脈是提供頭部、頸部和大腦血液的血管。

細懸浮微粒是由直徑小於2.5微米或30分之1人髮寬度的灰塵顆粒、沙土、煤煙、煙霧和液體所組成,產生自汽車、發電廠和其他燃燒源。這些顆粒可以懸浮在空氣中很長一段時間。

顆粒較大或顏色較暗,看起來就是煙塵或煙霧。有些顆粒較小,只能用電子顯微鏡檢測。

這項研究的科學家還發現,當細懸浮微粒空氣污染隨著時間減少,血管壁厚度增加的速度也減緩。科學家表示,頸動脈的厚度是全身動脈硬化狀況的指標,在沒有明顯心臟病症狀的人身上也是如此。

研究人員追蹤5,362位45-84歲、來自美國6個大都市的民眾,進行多種族動脈粥狀硬化和空氣污染研究(MESA Air)。

科學家針對每位受試者家中的空氣污染程度、以及超音波血管壁測量結果進行2次比對,2次之間間隔3年,發現兩者存在關聯性。

研究人員調整了吸菸等其他因素後發現,一般來說,頸動脈血管厚度平均每年增加14微米。

住家的細懸浮微粒空氣污染程度較高的人,血管增厚速度比其他居住在相同都會區內的人要快。

「綜合其他針對同樣人口進行的研究發現,同一都會區內,居住在空氣污染較嚴重地區的人,和居住在空氣污染程度較輕地區的人相比,中風機率高出2個百分點。」Adar說

「如果未來10年的追蹤調查結果也是如此的話,」Adar說,「這些研究結果將有助於解釋長期的PM2.5濃度和臨床心血管事件之間的關聯。」

研究人員指出,影響心臟和血管功能的心血管疾病,是全球疾病和死亡的主要原因之一。以美國為例,冠狀動脈疾病是成年人的主要死因;動脈粥狀硬化斑塊,也就是隨年齡增長在血管壁沈積的脂肪,讓心臟的動脈變窄,使流到心臟的血液變少,最終導致心臟病發。

美國第四大主要死因是中風。中風是動脈粥狀硬化斑塊導致腦部的血液供應中斷。吸菸、高血壓、高血膽固醇、糖尿病、體重超重、身體活動減少等都會增加心血管疾病發生的風險。治療方法包括改變生活習慣和服用藥物,降低血壓或血液中的膽固醇水平。

Air Pollution Linked to Hardening of the Arteries
ANN ARBOR, Michigan, April 30, 2013 (ENS)

Long term exposure to air pollution is linked to heart attacks and strokes because it speeds up hardening of the arteries, known as atherosclerosis, according to University of Michigan scientists and colleagues from across the United States.

Sara Adar, an assistant professor of epidemiology at the U-M School of Public Health, and Joel Kaufman, professor of environmental and occupational health sciences and medicine at the University of Washington, led the study, published in this week's issue of the journal "PLOS Medicine."

"Our findings help us to understand how it is that exposures to air pollution may cause the increases in heart attacks and strokes observed by other studies," said Adar.

The scientists found that higher concentrations of fine particulate air pollution, PM2.5, were linked to faster thickening of the inner two layers of the carotid artery – a blood vessel that provides blood to the head, neck and brain.

Fine particulate matter consists of particles of dust, dirt, soot, smoke, and liquid with a diameter of less than 2.5 micrometers or 1/30th the width of a human hair. It is produced by motor vehicles, power plants, and other combustion sources. Particles can be suspended in the air for long periods of time.

Some particles are large or dark enough to be seen as soot or smoke. Others are so small that individually they can only be detected with an electron microscope.

The scientists on this study also found that reductions of fine particulate air pollution over time was linked to slower progression of the blood vessel thickness.

The thickness of the carotid artery is an indicator of how much hardening is present in the arteries throughout the body, even among people with no obvious symptoms of heart disease, the scientists say.

The researchers followed 5,362 people ages 45-84 from six U.S. metropolitan areas as part of the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air).

The scientists were able to link air pollution levels estimated at each person's house with two ultrasound measurements of the blood vessels, separated by about three years.

After adjusting for other factors such as smoking, the authors found that on average, the thickness of the carotid vessel increased by 14 micrometers each year.

The vessels of people exposed to higher levels of residential fine particulate air pollution thickened faster than others living in the same metropolitan area.

"Linking these findings with other results from the same population suggests that persons living in a more polluted part of town may have a two percent higher risk of stroke as compared to people in a less polluted part of the same metropolitan area," Adar said.

"If confirmed by future analyses of the full 10 years of follow-up in this cohort," she said, "these findings will help to explain associations between long-term PM2.5 concentrations and clinical cardiovascular events."

Cardiovascular disease, which affects the heart and blood vessels, is a major cause of illness and death worldwide, the researchers explain. In the United States, for example, the leading cause of death among adults is coronary artery disease, in which narrowing of the heart's arteries by atherosclerotic plaques – fatty deposits that build up with age inside arteries – slows the blood supply to the heart and may eventually cause a heart attack.

The fourth leading cause of death in the United States is stroke, in which atherosclerotic plaques interrupt the brain's blood supply. Smoking, high blood pressure, high blood cholesterol levels, diabetes, being overweight, and being physically inactive all increase an individual's risk of developing cardiovascular disease. Treatments include lifestyle changes and taking drugs that lower blood pressure or blood cholesterol levels.

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