Population Research Laboratory, Department of Sociology, Social Work, and Anthropology, Utah State University, Logan, UT, USA.
Popul Health Metr. 2009 Jan 6;7:2. doi: 10.1186/1478-7954-7-2.
Data from the National Health Interview Survey (NHIS) show a larger-than-expected increase in mean BMI between 1996 and 1997. Proxy-reports of height and weight were discontinued as part of the 1997 NHIS redesign, suggesting that the sharp increase between 1996 and 1997 may be artifactual.
We merged NHIS data from 1976-2002 into a single database consisting of approximately 1.7 million adults aged 18 and over. The analysis consisted of two parts: First, we estimated the magnitude of BMI differences by reporting status (i.e., self-reported versus proxy-reported height and weight). Second, we developed a procedure to correct biases in BMI introduced by reporting status.
Our analyses confirmed that proxy-reports of weight tended to be biased downward, with the degree of bias varying by race, sex, and other characteristics. We developed a correction procedure to minimize BMI underestimation associated with proxy-reporting, substantially reducing the larger-than-expected increase found in NHIS data between 1996 and 1997.
It is imperative that researchers who use reported estimates of height and weight think carefully about flaws in their data and how existing correction procedures might fail to account for them. The development of this particular correction procedure represents an important step toward improving the quality of BMI estimates in a widely used source of epidemiologic data.
国家健康访谈调查（NHIS）的数据显示，1996 年至 1997 年间，平均 BMI 呈预期之外的大幅上升。作为 1997 年 NHIS 重新设计的一部分，身高和体重的代理报告被停止，这表明 1996 年至 1997 年之间的急剧上升可能是人为的。
我们将 1976 年至 2002 年的 NHIS 数据合并到一个单一的数据库中，该数据库包含约 170 万 18 岁及以上的成年人。该分析包括两部分：首先，我们通过报告状态（即自我报告与代理报告的身高和体重）来估计 BMI 差异的幅度。其次，我们开发了一种程序来纠正报告状态引起的 BMI 偏差。
我们的分析证实，体重的代理报告往往存在向下偏差，偏差的程度因种族、性别和其他特征而异。我们开发了一种纠正程序，以最大限度地减少代理报告引起的 BMI 低估，这大大降低了 NHIS 数据中 1996 年至 1997 年之间发现的高于预期的增长。
使用身高和体重报告数据的研究人员必须认真考虑数据中的缺陷，以及现有纠正程序可能无法解决的问题。开发这种特定的纠正程序是朝着提高广泛使用的流行病学数据中 BMI 估计质量迈出的重要一步。
