Friedenreich C M, Brant R F, Riboli E
Department of Community Health Sciences, University of Calgary, Alberta, Canada.
Epidemiology. 1994 Jan;5(1):66-79. doi: 10.1097/00001648-199401000-00011.
We examined the study design features and data collection methods from 13 case-control studies of colorectal cancer and diet, which had been previously combined and analyzed, to determine whether they influenced the results obtained from a pooled analysis. We assessed the methods used in each study, estimated a quality score, and used random effects models to re-estimate the pooled odds ratio for the association between dietary fiber and colorectal cancer for these data. Key features of the methods used in each study and the quality score were examined in random effects models to determine whether the heterogeneity found between study-specific risk estimates could be explained by these variables. The odds ratio for dietary fiber and colorectal cancer was 0.46 (95% confidence interval = 0.34-0.64) for the 13 case-control studies as estimated with a random effects model. Two factors, whether the diet questionnaire had been validated before use in the case-control study and whether qualitative data on dietary habits and cooking methods had been incorporated into the nutrient estimation, explained some of the heterogeneity found between studies. Risk estimates for dietary fiber and colorectal cancer were closer to the null for the studies that had these two characteristics. Quality score did not explain any between-study heterogeneity. Random effects models, which included fixed effects covariates, explained some between-study heterogeneity in these data and would be useful for future pooled analyses.
我们检查了13项关于结直肠癌与饮食的病例对照研究的研究设计特征和数据收集方法，这些研究此前已进行合并分析，以确定它们是否影响了汇总分析所得结果。我们评估了每项研究中使用的方法，估算了质量得分，并使用随机效应模型重新估算这些数据中膳食纤维与结直肠癌关联的汇总比值比。在随机效应模型中检查了每项研究中使用的方法的关键特征和质量得分，以确定特定研究风险估计值之间发现的异质性是否可以由这些变量来解释。使用随机效应模型估算，13项病例对照研究中膳食纤维与结直肠癌的比值比为0.46（95%置信区间=0.34-0.64）。两个因素，即饮食问卷在病例对照研究中使用前是否经过验证，以及饮食习惯和烹饪方法的定性数据是否已纳入营养估算，解释了研究之间发现的部分异质性。具有这两个特征的研究中，膳食纤维与结直肠癌的风险估计值更接近无效值。质量得分并未解释任何研究间的异质性。包含固定效应协变量的随机效应模型解释了这些数据中部分研究间的异质性，对未来的汇总分析将很有用。
