中风发生率与空气质量不佳有关


  【24drs.com】新研究显示,美国和中国空气质量不佳的地区,中风发生率相对较高,且气温较高时会使这个关系恶化。
  
  第一作者、宾州费城卓克索大学流行病学暨生物统计学副教授Longjian Liu博士等人在结论中表示,这篇研究使用了具有全国代表性的资料,首度提出空气质量与中风发生率之间有正向且复杂的关联,且气温对于空气与中风之关联也可能有所影响。
  
  这些研究结果发表于2016国际中风研讨会(International Stroke Conference [ISC]2016)。
  
  虽然有关空气质量不佳的不良健康影响已有诸多论述,Liu博士等人假设,空气污染率高的地区,中风比率可能比较高。
  
  研究者检视了美国49州的空气污染资料,包含2010-2013年的微粒物质估计测量,也探讨了中国32省、120个城市的资料,2012-2013年的空污指数(API)测量。
  
  Liu博士在美国中风协会新闻稿中表示,选择美国和中国进行研究,是因为这两国是世界上最大的两个温室气体排放国,迄今为止、与大约三分之一的全球暖化有关。
  
  比较中风测量资料后,研究者发现,美国的中风发生率确实和污染程度有关 — 直径小于2.5 μm的微粒物质(PM2.5)浓度每增加10 μg/m3,中风发生率即增加达1.19%;已知,PM2.5因为体积小,而带有相当大的健康风险(P < .001)。
  
  美国各州的微粒指标明显各异(P = .01)、各月份的差异也是,7月时最高(10.2 μg/m3),10月时最低(7.63 μg/m3)。
  
  作者们报告指出,年度PM2.5平均值最高的,是美国的南部区域,最低的是西部区域,中风发生率最高的也是南部(4.2%),最低的也是西部(3%)。
  
  在中国,API浓度较高的城市中风发生率也显著较高,而空气质量与中风风险之关联受到气温显著影响。
  
  中国API值最高的月份是12月,2012年时为75.76 、2013年时为97.51,最低的月份是7月,2012年时为51.21、2013年时为54.23。
  
  Liu博士表示,高温造成关键的热应力,导致中风风险、其它与热及空气质量有关的疾病和死亡增加。
  
  另外,在夏天时,中风患者处于因高温而脱水的危险,冬天时则是处于患肺炎、流行性感冒与其它呼吸道疾病的危险;女性与年长者更可能因为空气质量和热相关疾病而面临中风风险。
  
  南卡罗来纳医学大学流行病学暨神经科教授Daniel T. Lackland博士受邀对研究结果发表评论时表示,还未充分了解空污和中风之关联的机转;当然,我们正在寻找与中风的疾病负担有关的原因和因素,我们还未能一解全貌。
  
  污染有生态上的关联,但仍知之甚少。例如,曝露于空气污染者的高血压控制差,会导致更大的疾病风险。
  
  此外,重要的注意事项包括,在了解暴露于恶劣空气之质量和中风风险程度上,有所困难。
  
  Lackland博士表示,原因在于「量化」曝露程度上的难度。大部份的人是没有曝露的,因为大多数时间是在一个「气候」控制的环境内(如空调等等)。
  
  美国心脏协会(AHA)的科学声明,已经在2010年提出PM2.5的不良健康影响(https://circ.ahajournals.org/content/121/21/2331.full.pdf+html),美国心脏协会在该声明的结论指出,PM2.5曝露情况是造成心血管发病率和死亡率的一个可调控因素。
  
  声明的结论指出,即便近几周内只有曝露于PM2.5几小时,也会诱发心血管疾病相关死亡率和非致命事件,长期曝露会使心血管死亡率风险增加更大幅度。
  
  同样的,即使只是短暂几年,PM值降低与心血管死亡率降低有关;许多可信的病理机制,已经阐明这些研究结果的生物合理性。
  
  在风险背后的机转方面,证据指出PM2.5和全身性发炎、发炎前生物标记上升的关联,这表示,在吸入污染物之后的反应,不局限于影响肺部。
  
  资料来源: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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