Samoli E, Touloumi G, Zanobetti A, Le Tertre A, Schindler Chr, Atkinson R, Vonk J, Rossi G, Saez M, Rabczenko D, Schwartz J, Katsouyanni K
Department of Hygiene and Epidemiology, University of Athens, Medical School, Athens 115 27, Greece.
Occup Environ Med. 2003 Dec;60(12):977-82. doi: 10.1136/oem.60.12.977.
Several recent studies have reported significant health effects of air pollution even at low levels of air pollutants, but in most of these studies linear non-threshold relations were assumed.
To investigate the NO2 mortality dose-response association in nine cities participating in the APHEA-2 project using two different methods: the meta-smooth and the cubic spline method.
The meta-smooth method developed by Schwartz and Zanobetti is based on combining individual city non-parametric smooth curves; the cubic spline method developed within the APHEA-2 project combines individual city estimates of cubic spline shaped dose-response relations. The meta-smooth method is easier and faster to implement, but the cubic spline method is more flexible for further investigation of possible heterogeneity in the dose-response curves among cities.
In the range of the pollutant common to all cities the two methods gave similar and comparable curves. Using the cubic spline method it was found that smoking prevalence acts as an effect modifier with larger NO2 effects on mortality at lower smoking prevalence.
The NO2-mortality association in the cities included in the present analysis, could be adequately estimated using the linear model. However, investigation of the city specific dose-response curves should precede the application of linear models.
最近的几项研究报告称，即使空气污染物浓度较低，空气污染也会对健康产生重大影响，但在大多数这些研究中，都假定了线性无阈值关系。
使用两种不同方法，即元平滑法和三次样条法，调查参与APHEA - 2项目的九个城市中二氧化氮死亡率的剂量反应关联。
施瓦茨和扎诺贝蒂开发的元平滑法基于合并各个城市的非参数平滑曲线；APHEA - 2项目中开发的三次样条法结合了各个城市对三次样条形状剂量反应关系的估计。元平滑法实施起来更简便快捷，但三次样条法在进一步研究城市间剂量反应曲线可能存在的异质性方面更灵活。
在所有城市共有的污染物范围内，两种方法得出了相似且可比的曲线。使用三次样条法发现，吸烟率起到效应修饰作用，在吸烟率较低时，二氧化氮对死亡率的影响更大。
本分析中纳入的城市里，二氧化氮与死亡率的关联可以使用线性模型进行充分估计。然而，在应用线性模型之前，应先调查特定城市的剂量反应曲线。
