Lung cancer risk at low asbestos exposure: meta-regression of the exposure-response relationship
该研究通过元回归分析19项研究的104个风险估计值，发现低水平石棉暴露下肺癌相对风险可能高于以往预期，并揭示了不同纤维类型间的效力差异。
<h3>Objectives</h3> Most previous lung cancer studies focused on individuals heavily exposed to asbestos. Therefore, the existing estimated lung cancer risks per unit of exposure are mainly based on, and applicable to, high exposures. However, increasing interest lies in estimating risk at low exposures. <h3>Methods</h3> We fitted linear and non-linear meta-regression models to 104 aggregated risk estimates extracted from 19 asbestos lung cancer studies. Associated RRs were calculated for several low cumulative asbestos exposure levels. The sensitivity of these RRs to the inclusion or exclusion of specific studies was assessed. <h3>Results</h3> A natural spline model fitted our data best. With this model the relative lung cancer risk for cumulative exposures levels of 0.1 f-y/ml, 4 f-y/ml, and 40 f-y/ml was estimated to lie between 1.000 and 1.001, 1.013 and 1.027, and 1.13 and 1.30, respectively. After stratification by fibre type, a three to fourfold difference in RRs between chrysotile and amphibole fibres was found for exposures below 40 f-y/ml. Fibre type-specific risk estimates were strongly influenced by a few studies. <h3>Conclusions</h3> The natural spline regression model indicated that at lower asbestos exposure levels, the increase in RR of lung cancer due to asbestos exposure may be larger than expected from previous meta-analyses. Heterogeneity in the results, however, limited accurate assessment of potency differences between different fibre types. Low exposed industry or population-based cohorts with quantitative estimates of asbestos exposure are required to substantiate the risk estimates at low exposure levels from our new, flexible meta-regression.