Chen Yin-Hsiu, Ferguson Kelly K, Meeker John D, McElrath Thomas F, Mukherjee Bhramar
Department of Biostatistics, University of Michigan School of Public Health, Ann Arbor, MI, USA.
Department of Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, MI, USA.
Environ Health. 2015 Jan 26;14:9. doi: 10.1186/1476-069X-14-9.
It is of critical importance to evaluate the role of environmental chemical exposures in premature birth. While a number of studies investigate this relationship, most utilize single exposure measurements during pregnancy in association with the outcome. The studies with repeated measures of exposure during pregnancy employ primarily cross-sectional analyses that may not be fully leveraging the power and additional information that the data provide.
We examine 9 statistical methods that may be utilized to estimate the relationship between a longitudinal exposure and a binary, non-time-varying outcome. To exemplify these methods we utilized data from a nested case-control study examining repeated measures of urinary phthalate metabolites during pregnancy in association with preterm birth.
The methods summarized may be useful for: 1) Examining sensitive windows of exposure in association with an outcome; 2) Summarizing repeated measures to estimate the relationship between average exposure and an outcome; 3) Identifying acute exposures that may be relevant to the outcome; and 4) Understanding the contribution of temporal patterns in exposure levels to the outcome of interest. In the study of phthalates, changes in urinary metabolites over pregnancy did not appear to contribute significantly to preterm birth, making summary of average exposure across gestation optimal given the current design.
The methods exemplified may be of great use in future epidemiologic research projects intended to: 1) Elucidate the complex relationships between environmental chemical exposures and preterm birth; 2) Investigate biological mechanisms in prematurity using repeated measures of maternal factors throughout pregnancy; and 3) More generally, address the relationship between a longitudinal predictor and a binary, non-time-varying outcome.
评估环境化学物质暴露在早产中的作用至关重要。虽然有许多研究调查这种关系，但大多数研究在孕期采用单次暴露测量并将其与结果相关联。那些在孕期对暴露进行重复测量的研究主要采用横断面分析，可能无法充分利用数据所提供的能力和额外信息。
我们研究了9种可用于估计纵向暴露与二元、非随时间变化的结果之间关系的统计方法。为了举例说明这些方法，我们利用了一项巢式病例对照研究的数据，该研究调查了孕期尿邻苯二甲酸酯代谢物的重复测量与早产的关系。
总结的这些方法可能有助于：1）检查与结果相关的敏感暴露窗口；2）汇总重复测量数据以估计平均暴露与结果之间的关系；3）识别可能与结果相关的急性暴露；4）了解暴露水平的时间模式对感兴趣结果的贡献。在邻苯二甲酸酯的研究中，孕期尿代谢物的变化似乎对早产没有显著贡献，鉴于当前的设计，对整个孕期的平均暴露进行汇总最为合适。
所举例的这些方法在未来的流行病学研究项目中可能非常有用，这些项目旨在：1）阐明环境化学物质暴露与早产之间的复杂关系；2）通过在整个孕期对母体因素进行重复测量来研究早产的生物学机制；3）更广泛地说，解决纵向预测因素与二元、非随时间变化的结果之间的关系。
