Response to "Biased Corrections or Biased About Corrections"
Response to "Biased Corrections or Biased About Corrections"
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对“有偏见的纠正或对纠正有偏见”的回应
DOI：
10.1038/oby.2009.13
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
Gail,MitchellH
中科院分区：
文献类型：
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作者：
Flegal,KatherineM;Graubard,BarryI;Williamson,DavidF;Gail,MitchellH
格林伯格教授提供的表格（1）澄清了他在前一篇文章（2）中使用的程序。他计算了一个亚组中因肥胖而死亡的比例，他说这个亚组没有严重的疾病。然后，他将整个样本中的所有死亡人数乘以相同的比例，试图估计如果整个样本中没有严重疾病，整个样本中会发生的肥胖导致的死亡人数。然而，如果整个样本中没有严重疾病，总死亡人数也会少得多（假设严重疾病会增加死亡率）。格林伯格正在计算一个假设的人口，其中没有严重疾病的人，但仍然有相同的死亡人数，包括严重疾病的人，可归因于肥胖的死亡。因此，他的方法大大高估了在没有严重疾病的情况下肥胖导致的死亡人数。尽管格林伯格称这些估计值为肥胖导致死亡的“最大校正值”，但这些不是校正值。他的方法没有考虑严重疾病对死亡率的任何影响，也没有正确计算如果整个样本中没有严重疾病，预测的肥胖相关死亡人数。此外，为了使来自无严重疾病的亚组的可归因分数适用于格林伯格假设的无严重疾病的人群，假设的整个人群不仅必须具有与亚组相同的BMI特异性风险比，而且还必须具有与亚组相同的BMI和混杂因素的联合分布。格林伯格的程序是错误的另一种变体，部分校正方法，其中相对风险或风险比针对混杂因素（在这种情况下，严重疾病）进行校正（在这种情况下，通过分层），但忽略混杂因素对死亡率本身的影响（3; 4）。正如我们在前面提到的（5），格林伯格的方法没有估计感兴趣的数量，不能推荐用于估计“校正的”归因死亡，并且对Flegal等人的估计几乎没有影响（6）。
The tabulations supplied by Professor Greenberg (1) clarify the procedures that he used in his previous article (2). He calculated the proportion of deaths attributable to obesity within a subgroup that he says had no serious illness. He then multiplied all the deaths in the whole sample by that same proportion to try to estimate the number of obesity-attributable deaths that would have occurred in the whole sample if there had been no serious illness in the whole sample. However, if there had been no serious illness in the whole sample, there would also have been far fewer total deaths (assuming that serious illness increases mortality). Greenberg is calculating deaths attributable to obesity for a hypothetical population that has no persons with serious illness but still has the same numbers of deaths as a population that includes people with serious illness. Thus, his procedure greatly over-estimates the number of obesityattributable deaths that would occur if there was no serious illness. Although Greenberg calls these estimates the “maximum corrected values” of deaths attributable to obesity, these are not corrected values. His method makes no allowance for any impact of serious illness on mortality and does not correctly calculate the number of obesity-associated deaths that would be predicted if there was no serious illness in the whole sample. In addition, in order for the attributable fraction from the subgroup without serious illness to apply to Greenberg’s hypothetical population without serious illness, that hypothetical whole population would have to have not only BMI-specific hazard ratios identical to those in the subgroup but also a joint distribution of BMI and confounders that was identical to that in the subgroup.Greenberg’s procedure is another variant of the incorrect, partially adjusted method in which relative risks or hazard ratios are adjusted (in this case by stratification) for a confounder (in this case, serious illness), but the effect of the confounder on mortality itself is ignored (3; 4). As we noted previously (5), Greenberg’s procedures do not estimate the quantities of interest, cannot be recommended to estimate “corrected” attributable deaths, and have little bearing on the estimates by Flegal et al (6).