Conforti P M
Environ Health Perspect. 1983 Nov;53:69-78. doi: 10.1289/ehp.835369.
Two previous studies (1969-1971 and 1969-1974) examined the association between cancer incidence and chrysotile asbestos ingested through drinking water in the San Francisco-Oakland Standard Metropolitan Statistical Area (SMSA). Population density, an important covariable in the association between cancer and environmental agents, was not included in the analyses of these studies. The present work determines the effect of this covariable on the results of the second San Francisco-Oakland SMSA study. The original and reanalyzed results are compared to reassess the association between cancer and asbestos. The only change in the regression procedures of the original studies was the addition of population density as an independent variable in the reanalysis. The results of the reanalysis showed that population density had little effect on the results of the second study. Slightly more significance was found for asbestos regression coefficients in the reanalysis, including population density, than in the original analysis. These regression coefficients for asbestos indicated a positive association between ingested chrysotile asbestos and some cancer body sites. The conclusion of the reanalysis was that population density was distributed across the San Francisco-Oakland SMSA in such a way that it had little effect on the observation of an association between ingested asbestos and cancer.
之前的两项研究（1969 - 1971年和1969 - 1974年）考察了旧金山 - 奥克兰标准大都市统计区（SMSA）通过饮用水摄入温石棉与癌症发病率之间的关联。在这些研究的分析中，未纳入人口密度这一癌症与环境因素关联中的重要协变量。本研究确定了该协变量对旧金山 - 奥克兰SMSA第二项研究结果的影响。对原始结果和重新分析结果进行比较，以重新评估癌症与石棉之间的关联。原始研究回归程序的唯一变化是在重新分析中增加了人口密度作为自变量。重新分析结果表明，人口密度对第二项研究结果影响甚微。在纳入人口密度的重新分析中，石棉回归系数比原始分析中略显显著。这些石棉回归系数表明摄入的温石棉与某些癌症发病部位之间存在正相关。重新分析的结论是，人口密度在旧金山 - 奥克兰SMSA的分布方式使其对摄入石棉与癌症之间关联的观察影响不大。
