Bigman Galya
Institute of Human Virology, University of Maryland Baltimore, School of Medicine, Baltimore, Maryland.
Breastfeed Med. 2020 Feb;15(2):114-116. doi: 10.1089/bfm.2019.0269. Epub 2019 Dec 19.
Although reverse causation is well known in the breastfeeding-allergy arena, only a few studies have used a valid statistical method to test its occurrence. This study aimed to illustrate reverse causation between eczema and breastfeeding and to examine their effect estimate under this occurrence. Time-to-event data from the Infant Feeding Practices Study II were used. Model 1: early signs of eczema were modeled as a time-varying covariate to assess reverse causation using survival analysis approach. Model 2 examined the crude and adjusted relative risk between breastfeeding and early signs of eczema using generalized linear model. Overall, 2,350 mother-infant pairs were included. On average, infants with early signs of eczema versus without, breastfed for 5.2 ± 0.2 months compared with 4.10 ± 0.1, respectively. Model 1, an early sign of eczema, was associated with approximately a 16% (95% confidence interval 2-28) reduction in the risk of ceasing breastfeeding indicating reverse causation. Model 2, each month of breastfeeding increased the risk for early signs of eczema by 3%. Modeling early signs of eczema as a time-varying covariate using survival analysis approach detects reverse causation and children with early signs of eczema were breastfed for longer duration. Failure to account for reverse causation may create biased result and a conclusion where breastfeeding increases the risk for early signs for eczema. Future studies should perceive reverse causation by using time-varying covariate in survival analysis approach.
尽管在母乳喂养与过敏领域，反向因果关系广为人知，但仅有少数研究采用有效的统计方法来检验其是否存在。本研究旨在阐明湿疹与母乳喂养之间的反向因果关系，并在此情况下检验它们的效应估计值。使用了来自婴儿喂养实践研究II的事件发生时间数据。模型1：将湿疹的早期迹象作为一个随时间变化的协变量进行建模，采用生存分析方法评估反向因果关系。模型2使用广义线性模型检验母乳喂养与湿疹早期迹象之间的粗相对风险和调整后的相对风险。总体而言，纳入了2350对母婴。平均而言，有湿疹早期迹象的婴儿与没有湿疹早期迹象的婴儿相比，母乳喂养时间分别为5.2±0.2个月和4.10±0.1个月。模型1中，湿疹的早期迹象与停止母乳喂养风险降低约16%（95%置信区间2%-28%）相关，表明存在反向因果关系。模型2中，母乳喂养的每个月会使湿疹早期迹象的风险增加3%。使用生存分析方法将湿疹的早期迹象作为随时间变化的协变量进行建模可检测到反向因果关系，且有湿疹早期迹象的儿童母乳喂养时间更长。未考虑反向因果关系可能会产生有偏差的结果以及得出母乳喂养会增加湿疹早期迹象风险的结论。未来的研究应通过在生存分析方法中使用随时间变化的协变量来认识反向因果关系。
