Blomqvist N, Svärdsudd K
Scand J Soc Med. 1978;6(3):125-9. doi: 10.1177/140349487800600305.
Whether initial value affects blood pressure change or not is of interest in longitudinal blood pressure studies. The change/initial value relationship is, however, biased by the regression towards the mean phenomenon, as blood pressure measurements contain random errors (short-term intra-individual variation and measurement errors). Two methods (here called C and D) of avoiding this bias have earlier been proposed and used in population studies in South Wales and Framingham, with conflicting results. In the preceding paper a new method of avoiding the bias has been presented. In the present paper a comparison of the new method with the two earlier is made by applying them to the same data set. Method C indicates, as in South Wales, a highly significant positive relationship, while method D (as in Framingham) and the new method give a regression coefficient close to zero. The structure of the three methods is analysed. Method C is shown to be valid only under very restricted conditions and is best avoided. Method D gives a fairly accurate result, but underestimates the coefficient by approximately 30% in this case. The new method proposed seems to be the best method hitherto for this kind of analysis.
在纵向血压研究中，初始值是否会影响血压变化备受关注。然而，由于血压测量包含随机误差（个体内短期变异和测量误差），变化/初始值关系会受到均值回归现象的影响而产生偏差。此前已提出两种避免这种偏差的方法（这里称为方法C和方法D），并在南威尔士和弗雷明汉的人群研究中使用，但结果相互矛盾。在前一篇论文中，提出了一种避免偏差的新方法。在本文中，通过将新方法与前两种方法应用于同一数据集，对它们进行了比较。方法C显示出与南威尔士研究中一样的高度显著正相关关系，而方法D（如弗雷明汉研究中那样）和新方法得到的回归系数接近零。对这三种方法的结构进行了分析。结果表明，方法C仅在非常有限的条件下有效，最好避免使用。方法D给出了相当准确的结果，但在这种情况下大约低估了系数30%。所提出的新方法似乎是迄今为止用于此类分析的最佳方法。
