Modeling Variables With a Spike at Zero: Examples and Practical Recommendations
Modeling Variables With a Spike at Zero: Examples and Practical Recommendations
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DOI：
10.1093/aje/kww122
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发表时间：
2017-04-15
影响因子：
5
通讯作者：
Becher, Heiko
中科院分区：
文献类型：
--
作者：
Lorenz, Eva;Jenkner, Carolin;Becher, Heiko
在大多数流行病学研究和一般的临床研究中，存在峰值为零的变量，即一部分个体暴露为零的变量（例如，从不吸烟者），并且在暴露者中，变量具有连续分布。对这些变量进行建模有不同的选择，例如将未暴露者归类为参考组，或者通过将变量纳入回归模型（有或没有一些转换或建模程序）来忽略尖峰。它已被证明，这种情况下，可以通过添加一个二元指标（暴露/未暴露）的回归模型进行分析，并与它估计一个合适的函数形式的尖峰在零变量分布的正部分的分数多项式的基础上的方法已经开发。本文中，我们使用来自德国进行的3项病例对照研究的数据比较了不同的方法：乳腺癌风险因素调查（玛丽），2002-2005年进行的乳腺癌研究（Flesch-Janys et al.，Int J Cancer. 2008; 123（4）：933-941）; Rhein-Neckar Larynx Study，1998-2000年进行的喉癌研究（Dietz et al.，Int J Cancer. 2004; 108（6）：907-911）;和1988-1993年进行的肺癌研究（Jckel等人，国际流行病学杂志。1998; 27（4）：549-560）。论证了不同程序的优点和局限性，并给出了一些实际使用的建议。
In most epidemiologic studies and in clinical research generally, there are variables with a spike at zero, namely variables for which a proportion of individuals have zero exposure (e.g., never smokers) and among those exposed the variable has a continuous distribution. Different options exist for modeling such variables, such as categorization where the nonexposed form the reference group, or ignoring the spike by including the variable in the regression model with or without some transformation or modeling procedures. It has been shown that such situations can be analyzed by adding a binary indicator (exposed/nonexposed) to the regression model, and a method based on fractional polynomials with which to estimate a suitable functional form for the positive portion of the spike-at-zero variable distribution has been developed. In this paper, we compare different approaches using data from 3 case-control studies carried out in Germany: the Mammary Carcinoma Risk Factor Investigation (MARIE), a breast cancer study conducted in 2002-2005 (Flesch-Janys et al., Int J Cancer. 2008; 123(4): 933-941); the Rhein-Neckar Larynx Study, a study of laryngeal cancer conducted in 1998-2000 (Dietz et al., Int J Cancer. 2004; 108(6): 907-911); and a lung cancer study conducted in 1988-1993 (Jckel et al., Int J Epidemiol. 1998; 27(4): 549-560). Strengths and limitations of different procedures are demonstrated, and some recommendations for practical use are given.