Duke Global Health Institute, Duke University, Durham, NC 27705, USA.
Am J Epidemiol. 2010 Mar 15;171(6):664-73. doi: 10.1093/aje/kwp435. Epub 2010 Feb 5.
Confounding associated with social stratification or other selection processes has been called structural confounding. In the presence of structural confounding, certain covariate strata will contain only subjects who could never be exposed, a violation of the positivity or experimental treatment effect assumption. Thus, structural confounding can prohibit the exchangeability necessary for meaningful causal contrasts across levels of exposure. The authors explored the presence and magnitude of structural confounding by estimating the independent effects of neighborhood deprivation and neighborhood racial composition (segregation) on rates of preterm birth in Wake and Durham counties, North Carolina (1999-2001). Tabular analyses and random-intercept fixed-slope multilevel logistic models portrayed different structural realities in these counties. The multilevel modeling results suggested some nonsignificant effect of residence in tracts with high levels of socioeconomic deprivation or racial residential segregation on adjusted odds of preterm birth for white and black women living in these counties, and the confidence limit ratios indicated fairly consistent levels of precision around the estimates. The results of the tabular analysis, however, suggested that many of these regression modeling findings were off-support and based on no actual data. The implications for statistical and public health inference, in the presence of no data, are considered.
与社会分层或其他选择过程相关的混杂因素被称为结构混杂。在存在结构混杂的情况下，某些协变量层将只包含永远不可能暴露的对象，这违反了阳性或实验处理效果假设。因此，结构混杂可能会阻止在暴露水平上进行有意义的因果对比所需的可交换性。作者通过估计邻里剥夺和邻里种族构成（隔离）对北卡罗来纳州威克和达勒姆县（1999-2001 年）早产率的独立影响，探讨了结构混杂的存在和程度。表格分析和随机截距固定斜率多层逻辑模型描绘了这两个县不同的结构现实。多层次建模结果表明，对于居住在社会经济剥夺程度高或种族居住隔离程度高的地段的白人女性和黑人女性，居住在这些县的女性调整后的早产几率存在一些不显著的影响，置信限比表明围绕这些估计值的精度水平相当一致。然而，表格分析的结果表明，这些回归建模结果中的许多结果都缺乏支持，并且没有实际数据支持。在没有数据的情况下，考虑了对统计和公共卫生推断的影响。
