中風發生率與空氣品質不佳有關


  【24drs.com】新研究顯示,美國和中國空氣品質不佳的地區,中風發生率相對較高,且氣溫較高時會使這個關係惡化。
  
  第一作者、賓州費城卓克索大學流行病學暨生物統計學副教授Longjian Liu博士等人在結論中表示,這篇研究使用了具有全國代表性的資料,首度提出空氣品質與中風發生率之間有正向且複雜的關聯,且氣溫對於空氣與中風之關聯也可能有所影響。
  
  這些研究結果發表於2016國際中風研討會(International Stroke Conference [ISC]2016)。
  
  雖然有關空氣品質不佳的不良健康影響已有諸多論述,Liu博士等人假設,空氣汙染率高的地區,中風比率可能比較高。
  
  研究者檢視了美國49州的空氣汙染資料,包含2010-2013年的微粒物質估計測量,也探討了中國32省、120個城市的資料,2012-2013年的空汙指數(API)測量。
  
  Liu博士在美國中風協會新聞稿中表示,選擇美國和中國進行研究,是因為這兩國是世界上最大的兩個溫室氣體排放國,迄今為止、與大約三分之一的全球暖化有關。
  
  比較中風測量資料後,研究者發現,美國的中風發生率確實和汙染程度有關 — 直徑小於2.5 μm的微粒物質(PM2.5)濃度每增加10 μg/m3,中風發生率即增加達1.19%;已知,PM2.5因為體積小,而帶有相當大的健康風險(P < .001)。
  
  美國各州的微粒指標明顯各異(P = .01)、各月份的差異也是,7月時最高(10.2 μg/m3),10月時最低(7.63 μg/m3)。
  
  作者們報告指出,年度PM2.5平均值最高的,是美國的南部區域,最低的是西部區域,中風發生率最高的也是南部(4.2%),最低的也是西部(3%)。
  
  在中國,API濃度較高的城市中風發生率也顯著較高,而空氣品質與中風風險之關聯受到氣溫顯著影響。
  
  中國API值最高的月份是12月,2012年時為75.76 、2013年時為97.51,最低的月份是7月,2012年時為51.21、2013年時為54.23。
  
  Liu博士表示,高溫造成關鍵的熱應力,導致中風風險、其他與熱及空氣品質有關的疾病和死亡增加。
  
  另外,在夏天時,中風患者處於因高溫而脫水的危險,冬天時則是處於患肺炎、流行性感冒與其他呼吸道疾病的危險;女性與年長者更可能因為空氣品質和熱相關疾病而面臨中風風險。
  
  南卡羅來納醫學大學流行病學暨神經科教授Daniel T. Lackland博士受邀對研究結果發表評論時表示,還未充分瞭解空汙和中風之關聯的機轉;當然,我們正在尋找與中風的疾病負擔有關的原因和因素,我們還未能一解全貌。
  
  污染有生態上的關聯,但仍知之甚少。例如,曝露於空氣污染者的高血壓控制差,會導致更大的疾病風險。
  
  此外,重要的注意事項包括,在瞭解暴露於惡劣空氣之質量和中風風險程度上,有所困難。
  
  Lackland博士表示,原因在於「量化」曝露程度上的難度。大部份的人是沒有曝露的,因為大多數時間是在一個「氣候」控制的環境內(如空調等等)。
  
  美國心臟協會(AHA)的科學聲明,已經在2010年提出PM2.5的不良健康影響(https://circ.ahajournals.org/content/121/21/2331.full.pdf+html),美國心臟協會在該聲明的結論指出,PM2.5曝露情況是造成心血管發病率和死亡率的一個可調控因素。
  
  聲明的結論指出,即便近幾週內只有曝露於PM2.5幾小時,也會誘發心血管疾病相關死亡率和非致命事件,長期曝露會使心血管死亡率風險增加更大幅度。
  
  同樣的,即使只是短暫幾年,PM值降低與心血管死亡率降低有關;許多可信的病理機制,已經闡明這些研究結果的生物合理性。
  
  在風險背後的機轉方面,證據指出PM2.5和全身性發炎、發炎前生物標記上升的關聯,這表示,在吸入汙染物之後的反應,不侷限於影響肺部。
  
  資料來源:http://www.24drs.com/
  
  Native link:Stroke Prevalence Linked to Poor Air Quality

Stroke Prevalence Linked to Poor Air Quality

By Nancy A. Melville
Medscape Medical News

LOS ANGELES — Higher prevalence rates of stroke correspond to areas with poor air quality in the United States and China, with higher temperatures potentially exacerbating that relationship, new research shows.

"[This] study, using nationally representative data, is one of the first studies to address a positive and complex association between air quality and prevalence of stroke, and a potential interaction effect of temperatures on the air-stroke association," the researchers, with lead author Longjian Liu, MD, PhD, an associate professor of epidemiology and biostatistics at Drexel University in Philadelphia, Pennsylvania, conclude.

The results were presented here at the International Stroke Conference (ISC) 2016.

While many adverse health effects of poor air quality have been well documented, Dr Liu and his colleagues hypothesized that areas with high air pollution may have higher stroke rates.

For the study, the researchers looked at air pollution data from 49 states in the United States that included estimated measures of particulate matter from 2010 to 2013. They also looked at data from 120 cities in 32 provinces in China that had air pollution index (API) measures for 2012 to 2013.

The United States and China were selected because of their roles as "the world's two largest emitters of greenhouse gases and responsible for about one third of global warming to date," Dr Liu said in an American Stroke Association press statement.

Comparing the data with stroke measures, the researchers found that stroke prevalence rates in the United States did indeed correspond with pollution levels — increasing by 1.19% for every 10 μg/m3 of air increase in levels of particulate matter less than 2.5 μm in diameter (PM2.5), which is known to present the greatest health risk because of the small particulate size (P < .001).

Particulate matter levels in the United States varied significantly from state to state (P = .01), as well as from month to month, with the highest levels in July (10.2 μg/m3) and the lowest in October (7.63 μg/m3).

The highest average annual PM2.5 levels were seen in the southern region of the United States and the lowest were in the West, which correlate to the highest prevalence of stroke in the South (4.2%) compared with the lowest in the West (3%), the authors reported.

In China, stroke prevalence was also significantly higher in cities with higher API concentrations, while the associations between air quality and the risk for stroke were significantly mediated by temperatures.

The highest API in China was in December, with levels of 75.76 in 2012 and 97.51 in 2013, while the lowest levels were recorded in July, with levels of 51.21 in 2012 and 54.23 in 2013.

"High temperatures create a critical thermal stress that may lead to an increased risk for stroke and other heat- and air quality–related illnesses and deaths," Dr Liu said.

In addition, "patients with stroke are in danger of dehydration due to high temperatures in the summer and are in danger of suffering from pneumonia, influenza, and other respiratory diseases in winter. Women and the elderly also appear more vulnerable to stroke risk due to air quality and heat-related diseases," he said.

Asked to comment on the findings, Daniel T. Lackland, DrPH, professor of epidemiology and neurology at Medical University of South Carolina in Charleston, said the mechanisms linking air pollution with stroke are not well understood.

"Certainly we are looking for the reasons and factors associated with disease burden from stroke and we don't have all the answers," he told Medscape Medical News.

"Pollution has an ecological association but is still poorly understood. For example, the population exposed to air pollution may also have poor hypertension control, which leads to the excess disease risks."

Furthermore, important caveats include the difficulty in understanding the extent of exposure to poor air quality and stroke risk.

"What complicates this is the difficulty to quantify 'exposure'," Dr Lackland said.

"Most are not exposed as they spend most time in a 'climate'-controlled environment including air conditioning, et cetera."

The adverse health effects of PM2.5 have been acknowledged in an American Heart Association (AHA) Scientific Statement https://circ.ahajournals.org/content/121/21/2331.full.pdf+html issued in 2010, in which the AHA concluded, "PM2.5 exposure is deemed a modifiable factor that contributes to cardiovascular morbidity and mortality."

Exposure to PM2.5 even over the course of a few hours to weeks can trigger cardiovascular disease–related mortality and nonfatal events, the statement concludes, and longer-term exposure increases the risk for cardiovascular mortality to an even greater degree.

Likewise, "reductions in PM levels are associated with decreases in cardiovascular mortality within a time frame as short as a few years; and many credible pathological mechanisms have been elucidated that lend biological plausibility to these findings."

In terms of mechanisms behind the risk, evidence points to a link between PM2.5 and systemic inflammation and the elevation of proinflammatory biomarkers, suggesting a response that is not confined to the lung after inhalation of pollution.

The study was funded by a joint grant of Drexel (US)–SARI (China) Co-Research and Education on Low Carbon and Healthy City Technology Study. The authors and Dr Lackland have disclosed no relevant financial relationships.

International Stroke Conference (ISC) 2016. Abstract 36. Presented February 17, 2016.

    
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