Immortal Time Bias in the Study of Stillbirth Risk Factors The Example of Gestational Diabetes
Immortal Time Bias in the Study of Stillbirth Risk Factors The Example of Gestational Diabetes
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DOI：
10.1097/ede.0b013e3182a6d9aa
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发表时间：
2013-11-01
期刊：
影响因子：
5.4
通讯作者：
Lim, Kenneth
中科院分区：
文献类型：
--
作者：
Hutcheon, Jennifer A.;Kuret, Verena;Lim, Kenneth
背景资料：目前对妊娠期糖尿病死产风险增加的理解通常是基于大型队列研究，其中将患有这种疾病的妇女的死产风险与没有这种疾病的妇女的死产风险进行比较。然而，这样的研究可能容易受到不朽的时间偏差的影响，因为虽然许多队列开始在20周的妊娠，怀孕必须生存到24-28周，以筛选和诊断妊娠糖尿病。方法：我们描述了死产和妊娠期糖尿病研究中不朽时间偏倚的理论潜力，然后使用2006年美国生命统计数据量化偏倚的大小。统计数据。结果：虽然妊娠期糖尿病是防止死胎时，包括所有出生（相对危险度= 0.88 [95%可信区间= 0.79-0.99]），将分析限制在妊娠>28周的分娩，逆转了这种效应，糖尿病与死产风险增加相关（1.25 [1.11-1.41]）。结论：妊娠期糖尿病诊断前的死亡时间可能会使我们对与妊娠期糖尿病相关的死胎风险的理解产生偏差。
Background: Current understanding of the increased risk for stillbirth in gestational diabetes mellitus is often based on large cohort studies in which the risk of stillbirth in women with this disease is compared with the risk in women without. However, such studies could be susceptible to immortal time bias because, although many cohorts begin at 20 weeks' gestation, pregnancies must survive until 24-28 weeks in order to be screened and diagnosed with gestational diabetes.Methods: We describe the theoretical potential for immortal time bias in studies of stillbirth and gestational diabetes and then quantify the magnitude of the bias using 2006 United States vital statistics data.Results: Although gestational diabetes was protective against stillbirth when including all births (relative risk = 0.88 [95% confidence interval = 0.79-0.99]), restricting analyses to births at >28 weeks' gestation reversed the effect and diabetes became associated with an increased risk of stillbirth (1.25 [1.11-1.41]).Conclusion: Immortal time before diagnosis of gestational diabetes may bias our understanding of the stillbirth risk associated with this condition.