Vanke School of Public Health, Tsinghua University, Beijing, China.
Nicholas School of the Environment, Duke University, Durham, NC, USA.
Environ Health. 2022 Oct 13;21(1):97. doi: 10.1186/s12940-022-00901-8.
There is a discourse on whether air pollution mixture or air pollutant components are causally linked to increased mortality. In particular, there is uncertainty on whether the association of NO with mortality is independent of fine particulate matter (PM). Furthermore, effect modification by temperature on air pollution-related mortality also needs more evidence.
We used the Chinese Longitudinal Healthy Longevity Study (CLHLS), a prospective cohort with geographical and socio-economic diversity in China. The participants were enrolled in 2008 or 2009 and followed up in 2011-2012, 2014, and 2017-2018. We used remote sensing and ground monitors to measure nitrogen dioxide (NO), fine particulate matter (PM) , and temperature. We used the Cox-proportional hazards model to examine the association between component and composite air pollution and all-cause mortality, adjusted for demographic characteristics, lifestyle, geographical attributes, and temperature. We used the restricted cubic spline to visualize the concentration-response curve.
Our study included 11 835 individuals with an average age of 86.9 (SD: 11.4) at baseline. Over 55 606 person-years of follow-up, we observed 8 216 mortality events. The average NO exposure was 19.1 μg/m (SD: 14.1); the average PM exposure was 52.8 μg/m (SD: 15.9). In the single pollutant models, the mortality HRs (95% CI) for 10 μg/m increase in annual average NO or PM was 1.114 (1.085, 1.143) and 1.244 (1.221, 1.268), respectively. In the multi-pollutant model co-adjusting for NO and PM, the HR for NO turned insignificant: 0.978 (0.950, 1.008), but HR for PM was not altered: 1.252 (1.227, 1.279). PM and higher mortality association was robust, regardless of NO. When acccounting for particulate matter, NO exposure appeared to be harmful in places of colder climates and higher seasonal temperature variation.
We see a robust relationship of PM exposure and premature mortality in advance aged individuals, however, NO exposure and mortality was only harmful in places of colder climate such as northeast China, indicating evidence of effect modification by temperature. Analysis of NO without accounting for its collinearity with PM may lead to overestimation.
关于空气污染混合物或空气污染物成分是否与死亡率增加有因果关系存在争议。特别是，关于 NO 与死亡率之间的关联是否独立于细颗粒物 (PM) 存在不确定性。此外，关于温度对与空气污染相关的死亡率的影响修饰作用也需要更多证据。
我们使用了中国长寿纵向研究（CLHLS），这是一项在中国具有地理和社会经济多样性的前瞻性队列研究。参与者于 2008 年或 2009 年被招募，并在 2011-2012 年、2014 年和 2017-2018 年进行了随访。我们使用遥感和地面监测仪来测量二氧化氮 (NO)、细颗粒物 (PM) 和温度。我们使用 Cox 比例风险模型来检验成分和复合空气污染与全因死亡率之间的关联，调整了人口统计学特征、生活方式、地理属性和温度。我们使用限制性立方样条来可视化浓度-反应曲线。
我们的研究包括 11835 名基线时平均年龄为 86.9（标准差：11.4）的个体。在超过 55606 人年的随访中，我们观察到了 8216 例死亡事件。NO 的平均暴露量为 19.1μg/m（标准差：14.1）；PM 的平均暴露量为 52.8μg/m（标准差：15.9）。在单污染物模型中，每年平均 NO 或 PM 增加 10μg/m 的死亡率 HR（95%CI）分别为 1.114（1.085，1.143）和 1.244（1.221，1.268）。在多污染物模型中同时调整 NO 和 PM，NO 的 HR 变得不显著：0.978（0.950，1.008），但 PM 的 HR 没有改变：1.252（1.227，1.279）。PM 和更高的死亡率之间的关联是稳健的，与 NO 无关。当考虑到颗粒物时，NO 暴露在气候较冷和季节性温度变化较大的地区似乎是有害的。
我们发现 PM 暴露与高龄个体的过早死亡之间存在稳健的关系，然而，NO 暴露与死亡率之间的关联仅在气候较冷的地区（如中国东北地区）有害，表明温度的影响修饰作用存在证据。在没有考虑 PM 的共线性的情况下分析 NO 可能会导致高估。
