Maheswaran Ravi, Haining Robert P, Pearson Tim, Law Jane, Brindley Paul, Best Nicola G
Public Health GIS Unit, School of Health and Related Research, University of Sheffield, Regent Court, 30 Regent Street, Sheffield S1 4DA, UK.
Stat Methods Med Res. 2006 Oct;15(5):499-516. doi: 10.1177/0962280206071644.
There is increasing evidence, mainly from daily time series studies, linking air pollution and stroke. Small area level geographical correlation studies offer another means of examining the air pollution-stroke association. Populations within small areas may be more homogeneous than those within larger areal units, and census-based socioeconomic information may be available to adjust for confounding effects. Data on smoking from health surveys may be incorporated in spatial analyses to adjust for potential confounding effects but may be sparse at the small area level. Smoothing, using data from neighbouring areas, may be used to increase the precision of smoking prevalence estimates for small areas. We examined the effect of modelled outdoor NOx levels on stroke mortality using a Bayesian hierarchical spatial model to incorporate random effects, in order to allow for unmeasured confounders and to acknowledge sampling error in the estimation of smoking prevalence. We observed an association between NOx and stroke mortality after taking into account random effects at the small area level. We found no association between smoking prevalence and stroke mortality at the small area level after modelling took into account imprecision in estimating smoking prevalence. The approach we used to incorporate smoking as a covariate in a single large model is conceptually sound, though it made little difference to the substantive results.
越来越多的证据（主要来自每日时间序列研究）表明空气污染与中风之间存在关联。小区域层面的地理相关性研究提供了另一种检验空气污染与中风关联的方法。小区域内的人群可能比大区域单位内的人群更加同质化，并且可以获取基于人口普查的社会经济信息以调整混杂效应。来自健康调查的吸烟数据可纳入空间分析以调整潜在的混杂效应，但在小区域层面可能较为稀少。利用相邻区域的数据进行平滑处理，可用于提高小区域吸烟率估计的精度。我们使用贝叶斯分层空间模型来纳入随机效应，以检验模拟的室外氮氧化物水平对中风死亡率的影响，从而考虑未测量的混杂因素并承认吸烟率估计中的抽样误差。在考虑小区域层面的随机效应后，我们观察到氮氧化物与中风死亡率之间存在关联。在建模考虑了吸烟率估计中的不精确性之后，我们发现在小区域层面吸烟率与中风死亡率之间没有关联。我们在一个大型单一模型中将吸烟作为协变量纳入的方法在概念上是合理的，尽管对实质性结果影响不大。
