In studies of complex disorders such as nicotine dependence, it is common that researchers assess multiple variables related to a disorder as well as other disorders that are potentially correlated with the primary disorder of interest. In this work, we refer to those variables and disorders broadly as multiple traits. The multiple traits may or may not have a common causal genetic variant. Intuitively, it may be more powerful to accommodate multiple traits in genetic traits, but the analysis of multiple traits is generally more complicated than the analysis of a single trait. Furthermore, it is not well documented as to how much power we may potentially gain by considering multiple traits. Our aim is to enhance our understanding on this important and practical issue. We considered a variety of correlation structures between traits and the disease locus. To focus on the effect of accommodating multiple traits, we examined genetic models that are relatively simple so that we can pinpoint the factors affecting the power. We conducted simulation studies to explore the performance of testing multiple traits simultaneously and the performance of testing a single trait at a time in family-based association studies. Our simulation results demonstrated that the performance of testing multiple traits simultaneously is better than that of testing each trait individually for almost models considered. We also found that the power of association tests varies among the underlying models. The advantage of conducting a multiple traits test is minimized when some traits are influenced by the gene only through other traits; and it is maximized when there are causal relations between the traits and the gene, and among the traits themselves or when there are extraneous traits.

中文翻译：

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为什么我们在遗传关联研究中测试多种特征？

在对尼古丁依赖等复杂疾病的研究中，研究人员通常会评估与疾病相关的多个变量以及可能与感兴趣的原发性疾病相关的其他疾病。在这项工作中，我们将这些变量和障碍广义地称为多重特征。多个性状可能有也可能没有共同的因果遗传变异。直觉上，在遗传性状中容纳多个性状可能更强大，但多个性状的分析通常比单个性状的分析更复杂。此外，关于通过考虑多个特征我们可能获得多少权力，并没有得到很好的记录。我们的目标是增进我们对这一重要和实际问题的理解。我们考虑了性状和疾病基因座之间的各种相关结构。为了关注适应多个性状的影响，我们检查了相对简单的遗传模型，以便我们可以查明影响功率的因素。我们进行了模拟研究，以探索在基于家庭的关联研究中同时测试多个性状的性能和一次测试单个性状的性能。我们的模拟结果表明，对于所考虑的几乎模型，同时测试多个特征的性能优于单独测试每个特征的性能。我们还发现，关联测试的功效因基础模型而异。当某些性状仅通过其他性状受基因影响时，进行多性状测试的优势就被最小化了；