《柳叶刀》:研究证明空气污染对心肺功能有害

空气污染是许多城市的“顽疾”,但空气污染对心肺健康的影响一直未能肯定。近期,世界著名医学期刊《柳叶刀》杂志刊登了英国的一项研究,证实了空气污染对患有心肺疾病患者及健康人的影响。

研究背景:长期生活在空气污染中会导致肺功能下降的发病率增高,尤其是在老年人及患有慢性阻塞性肺病(COPD)的患者中。而且,短期暴露在空气污染中会增加缺血性心脏病患者的死亡率及COPD患者的急性发作。我们希望比较老年人在高空气污染道路相比车辆少、低污染的街道行走对呼吸及心血管系统的影响。


研究方法:在这项随机交叉研究中,我们招募了60岁以上血管成像证明有缺血性心脏病,或GOLD分级2级以上COPD男性及女性受试者,且临床稳定期至少6个月,以及年龄匹配的健康志愿者。患有缺血性心脏病或COPD的患者从现有数据库或呼吸和心血管科门诊招募,健康志愿者通过广告或现有数据库招募。所有受试者在研究过程中戒烟至少12个月,服药依据受试者医生的建议服用。受试者通过抽签随机分成两组,分别在伦敦商业街(牛津路)或郊区(海德公园)步行2小时。受试者的基线测量结果在步行之前在医院实验室完成。在每个步行区域测量黑碳、颗粒物(PM)浓度、超细颗粒物和二氧化氮(NO2)浓度。


研究结果:在2012年10月至2014年6月间,我们共筛选了135名受试者,其中招募了40名健康志愿者,40名COPD患者,以及39名缺血性心脏病患者。牛津街的黑碳、NO2、 PM10、PM2.5和超细颗粒物均高于海德公园。与在海德公园步行相比,患有COPD的受试者在牛津街步行报告咳嗽(风险比[OR] 1·95, 95% CI 0·96–3·95; p<0·1)、咳痰(3·15, 1·39–7·13; p<0·05)、气短(1·86, 0·97–3·57; p<0·1)和喘息(4·00, 1·52–10·50; p<0·05)的比例更高。无论是否患病,在海德公园步行的受试者肺功能有提升(第一秒用力呼气体积[FEV1]和用力肺活量[FVC]),脉搏传播速度下降(PWV),增强指数上升到26小时。相反,在牛津街步行后这些获益则有所下降。在患有COPD的受试者中,FEV1 及FVC的下降R5–20的升高与步行时暴露在NO2、超细颗粒物和PM2.5相关,PWV和增强指数的升高与NO2 和超细颗粒物相关。在健康志愿者中,PWV和增强指数与黑碳和超细颗粒物均相关。


研究解读:在COPD、缺血性心脏病患者和无慢性心肺疾患的人中,短期暴露于交通污染消除了步行带来的益处。药物可能会降低空气污染对缺血性心脏病患者带来的副作用。鉴于对健康的不良影响,我们需要制定政策控制交通繁忙道路的空气污染水平。


原文摘要


Background

Long-term exposure to pollution can lead to an increase in the rate of decline of lung function, especially in older individuals and in those with chronic obstructive pulmonary disease (COPD), whereas shorter-term exposure at higher pollution levels has been implicated in causing excess deaths from ischaemic heart disease and exacerbations of COPD. We aimed to assess the effects on respiratory and cardiovascular responses of walking down a busy street with high levels of pollution compared with walking in a traffic-free area with lower pollution levels in older adults.


Methods

In this randomised, crossover study, we recruited men and women aged 60 years and older with angiographically proven stable ischaemic heart disease or stage 2 Global initiative for Obstructive Lung Disease (GOLD) COPD who had been clinically stable for 6 months, and age-matched healthy volunteers. Individuals with ischaemic heart disease or COPD were recruited from existing databases or outpatient respiratory and cardiology clinics at the Royal Brompton & Harefield NHS Foundation Trust and age-matched healthy volunteers using advertising and existing databases. All participants had abstained from smoking for at least 12 months and medications were taken as recommended by participants' doctors during the study. Participants were randomly assigned by drawing numbered disks at random from a bag to do a 2 h walk either along a commercial street in London (Oxford Street) or in an urban park (Hyde Park). Baseline measurements of participants were taken before the walk in the hospital laboratory. During each walk session, black carbon, particulate matter (PM) concentrations, ultrafine particles, and nitrogen dioxide (NO2) concentrations were measured.


Findings

Between October, 2012, and June, 2014, we screened 135 participants, of whom 40 healthy volunteers, 40 individuals with COPD, and 39 with ischaemic heart disease were recruited. Concentrations of black carbon, NO2, PM10, PM2.5, and ultrafine particles were higher on Oxford Street than in Hyde Park. Participants with COPD reported more cough (odds ratio [OR] 1·95, 95% CI 0·96–3·95; p<0·1), sputum (3·15, 1·39–7·13; p<0·05), shortness of breath (1·86, 0·97–3·57; p<0·1), and wheeze (4·00, 1·52–10·50; p<0·05) after walking down Oxford Street compared with Hyde Park. In all participants, irrespective of their disease status, walking in Hyde Park led to an increase in lung function (forced expiratory volume in the first second [FEV1] and forced vital capacity [FVC]) and a decrease in pulse wave velocity (PWV) and augmentation index up to 26 h after the walk. By contrast, these beneficial responses were attenuated after walking on Oxford Street. In participants with COPD, a reduction in FEV1 and FVC, and an increase in R5–20 were associated with an increase in during-walk exposure to NO2, ultrafine particles and PM2.5, and an increase in PWV and augmentation index with NO2 and ultrafine particles. In healthy volunteers, PWV and augmentation index were associated both with black carbon and ultrafine particles.


Interpretation

Short-term exposure to traffic pollution prevents the beneficial cardiopulmonary effects of walking in people with COPD, ischaemic heart disease, and those free from chronic cardiopulmonary diseases. Medication use might reduce the adverse effects of air pollution in individuals with ischaemic heart disease. Policies should aim to control ambient levels of air pollution along busy streets in view of these negative health effects.


Reference: Respiratory and cardiovascular responses to walking down a traffic-polluted road compared with walking in a traffic-free area in participants aged 60 years and older with chronic lung or heart disease and age-matched healthy controls: a randomised, crossover study


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