Health Effects Institute, Boston, Massachusetts, USA.
Population Health Research Institute, St. George's University of London, London, United Kingdom.
Environ Health Perspect. 2023 Nov;131(11):115002. doi: 10.1289/EHP11532. Epub 2023 Nov 22.
There is a long tradition in environmental health of using frameworks for evidence synthesis, such as those of the U.S. Environmental Protection Agency for its Integrated Science Assessments and the International Agency for Research on Cancer Monographs. The framework, Grading of Recommendations Assessment, Development, and Evaluation (GRADE), was developed for evidence synthesis in clinical medicine. The U.S. Office of Health Assessment and Translation (OHAT) elaborated an approach for evidence synthesis in environmental health building on GRADE.
We applied a modified OHAT approach and a broader "narrative" assessment to assess the level of confidence in a large systematic review on traffic-related air pollution and health outcomes.
We discuss several challenges with the OHAT approach and its implementation and suggest improvements for synthesizing evidence from observational studies in environmental health. We consider the determination of confidence using a formal rating scheme of up- and downgrading of certain factors, the treatment of every factor as equally important, and the lower initial confidence rating of observational studies to be fundamental issues in the OHAT approach. We argue that some observational studies can offer high-confidence evidence in environmental health. We note that heterogeneity in magnitude of effect estimates should generally not weaken the confidence in the evidence, and consistency of associations across study designs, populations, and exposure assessment methods may strengthen confidence in the evidence. We mention that publication bias should be explored beyond statistical methods and is likely limited when large and collaborative studies comprise most of the evidence and when accrued over several decades. We propose to identify possible key biases, their most likely direction, and their potential impacts on the results. We think that the OHAT approach and other GRADE-type frameworks require substantial modification to align better with features of environmental health questions and the studies that address them. We emphasize that a broader, "narrative" evidence assessment based on the systematic review may complement a formal GRADE-type evaluation. https://doi.org/10.1289/EHP11532.
环境卫生领域有使用证据综合框架的悠久传统，例如美国环保署的综合科学评估和国际癌症研究机构专论。该框架，即推荐评估、制定和评价分级（GRADE），是为临床医学中的证据综合制定的。美国卫生评估和转化办公室（OHAT）在 GRADE 的基础上，详细阐述了一种用于环境卫生领域证据综合的方法。
我们应用了一种改良的 OHAT 方法和更广泛的“叙述性”评估，对一项关于交通相关空气污染与健康结果的大型系统评价的可信度进行评估。
我们讨论了 OHAT 方法及其实施中的几个挑战，并提出了改进意见，以综合环境卫生领域观察性研究的证据。我们认为使用正式的评级方案来确定可信度，即上调和下调某些因素的评级，以及将每个因素视为同等重要，以及将观察性研究的初始可信度评级降低，这些都是 OHAT 方法的基本问题。我们认为，一些观察性研究可以为环境卫生领域提供高可信度的证据。我们注意到，效应估计值的异质性通常不应削弱对证据的信心，而研究设计、人群和暴露评估方法之间的一致性则可能增强对证据的信心。我们提到，除了统计方法外，还应该探讨发表偏倚问题，并且当大部分证据来自大型合作研究，并且经过几十年的积累时，发表偏倚可能是有限的。我们建议确定可能存在的关键偏倚、其最可能的方向以及它们对结果的潜在影响。我们认为，OHAT 方法和其他 GRADE 型框架需要进行重大修改，以更好地适应环境卫生问题及其研究的特点。我们强调，基于系统评价的更广泛的“叙述性”证据评估可以补充正式的 GRADE 型评估。https://doi.org/10.1289/EHP11532.
