Background Many researchers have studied the relationship between diet and health. Specifically, there are papers showing an association between the consumption of sugar sweetened beverages and Type 2 diabetes. Many meta-analyses use individual studies that do not attempt to adjust for multiple testing or multiple modeling. Hence the claims reported in a meta-analysis paper may be unreliable as the base papers do not ensure unbiased statistics. Objective Determine (i) the statistical reliability of 10 papers and (ii) indirectly the reliability of the meta-analysis study. Method We obtained copies of each of the 10 papers used in a metaanalysis paper and counted the numbers of outcomes, predictors, and covariates. We estimate the size of the potential analysis search space available to the authors of these papers; i. e. the number of comparisons and models available. The potential analysis search space is the number of outcomes times the number of predictors times 2 c , where c is the number of covariates. This formula was applied to information found in the abstracts (Space A) as well as the text (Space T) of each base paper. Results The median and range of the number of comparisons possible across the base papers are 6.5 and (2 12,288), respectively for Space A, and 196,608 and (3072-117,117,952), respectively for Space T. It is noted that the median of 6.5 for Space A may be misleading as each study has 60-165 foods that could be predictors. Conclusion Given that testing is at the 5% level and the number of comparisons is very large, nominal statistical significance is very weak support for a claim. The claims in these papers are not statistically supported and hence are unreliable so the meta-analysis paper is also unreliable.

中文翻译：

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营养流行病学中的严重缺陷：荟萃分析研究。

背景许多研究人员研究了饮食与健康之间的关系。具体而言，有论文显示糖类甜味饮料的消费与2型糖尿病之间存在关联。许多荟萃分析使用的个别研究并不尝试针对多种测试或多种建模进行调整。因此，荟萃分析文件中报告的声明可能不可靠，因为基础文件不能确保统计数据的公正性。目的确定（i）10篇论文的统计信度和（ii）间接进行荟萃分析研究的信度。方法我们获得了荟萃分析论文中使用的10篇论文的每本的副本，并计算了结果，预测变量和协变量的数量。我们估计这些论文的作者可用的潜在分析搜索空间的大小；一世。e。可用的比较和模型的数量。潜在分析搜索空间是结果数乘以预测变量数乘以2 c，其中c是协变量数。该公式适用于每篇基础论文摘要（空格A）和文本（空格T）中的信息。结果对于空间A，可能在基础论文中进行比较的数目的中位数和范围分别为6.5和（2 12,288），对于空间T，可能进行比较的数目分别为196,608和（3072-117,117,952）。请注意，中位数6.5空间A可能会产生误导，因为每个研究都有60-165种食物可以作为预测指标。结论鉴于测试处于5％的水平并且比较的数量非常大，因此名义上的统计显着性对索赔的支持非常弱。