Natural and Unnatural Experiments in Epidemiology.
Natural and Unnatural Experiments in Epidemiology.
复制标题
DOI：
10.1097/ede.0000000000001242
复制
发表时间：
2020-11
期刊：
影响因子：
--
通讯作者：
Hamad R
中科院分区：
文献类型：
--
作者：
Hamad R
©2020 Wolters KluwerHealth，Inc.保留所有权利。www.w.前言。体重指数、腰围、低密度脂蛋白胆固醇和高密度脂蛋白胆固醇。由于研究中只有57个人是被迫流离失所的受害者，他们的健康结果是可用的，Shiba等人很好地将这一分析与更传统的固定影响分析结合在一起，在这一分析中，他们利用了1,630名未流离失所的人的更大样本中这些社区资源密度随时间的变化，得出了与自然实验相似的结果。任何采用自然实验的研究的强度取决于围绕自然实验本身的环境和(准)随机化的可信度。在Shiba等人的案例中，4名读者必须相信，在那些因地震而被迫流离失所的人中，分配到食物和娱乐目的地密度较高或较低的社区几乎是随机的。在这种情况下，满足这一标准将意味着，将个人分配到拖车之家或补贴公寓的政府官员没有关于研究对象的未观察到或未测量的特征(例如，健康状况、脆弱程度、家庭关系)的信息，这些特征可能改变了安置决定，也可能影响了相关的健康结果。类似地，研究对象本身必须在他们的位置上没有任何投入，否则自我选择的风险将导致与标准观察性研究相同的问题。支持这些断言的举证责任落在作者身上。在这种情况下，仔细检查日本政府的官方记录或采访受影响的个人，可能会澄清这一点，并加强自然实验的可信度。与标准的随机对照试验相比，自然实验更普遍的另一个限制是，研究人员无法控制所讨论的暴露的性质，而是依赖于改变暴露性质的自然或非自然环境。然而，在许多情况下，由于自然实验的结果而改变的条件是多方面的和相关的，因此很难梳理出暴露的显著特征。在这种情况下，作者感兴趣的是靠近食物和娱乐设施的影响。然而，这些特征很可能与其他社区特征相关，也可能与其他社区特征混淆，如住房质量、暴力犯罪和医疗保健获得，这些可能与感兴趣的结果相关。事实上，在日本，同样的自然实验之前也曾被用来研究邻里社会资本的影响。5尽管心脏代谢结果与食物和物理环境之间的理论联系加强了本研究的概念基础，但选择任何特定的社区特征作为兴趣的暴露在某种程度上是不分青红皂白的，因此结果不能被解释为明确地暗示接近食物和娱乐设施本身的影响。再一次，这对更广泛的邻里健康文献来说是一个挑战，因为邻里资源往往聚集在一起，这使得区分一个特定特征的影响具有挑战性。尽管这使得关于邻里关系可能影响健康的具体机制的理论很难推进，但它反映了个人生活的现实世界的复杂性。与此相关的是，欧盟委员会(…)
© 2020 Wolters Kluwer Health, Inc. All rights reserved. www. epidem. com| 769 mass index, waist circumference, and low-and high-density lipoprotein cholesterol. Because there were only 57 individuals in the study who were victims of the forced displacement and for whom health outcomes were available, Shiba et al4 commendably couple this analysis with a more traditional fixedeffects analysis, in which they instead leverage within-person variation in the density of these neighborhood resources over time in a larger sample of 1,630 individuals who were not displaced, with similar findings to the natural experiment. The strength of any study that employs a natural experiment hinges upon the circumstances surrounding the natural experiment itself and the credibility of the (quasi-) randomization. In the case of Shiba et al, 4 readers must be convinced that—among those who were forcibly displaced as a result of the earthquake—assignment to neighborhoods of higher or lower density of food and recreation destinations was as good as random. In this case, satisfying this criteria would mean that the government officials who assigned individuals into the trailer homes or subsidized apartments did not have information on unobserved or unmeasured characteristics of the study subjects (eg, health status, frailty, family connections) that may have altered placement decisions and may have also influenced the health outcomes in question. Similarly, the study subjects themselves would have had to have had no input into their placement, or else the risk of self-selection would lead to the same problems as in a standard observational study. The burden of proof for supporting these assertions rests with the authors. In this case, a closer examination of official Japanese government records or interviews with affected individuals might clarify this point and strengthen the credibility of the natural experiment. Another limitation of natural experiments more generally, compared with standard randomized controlled trials, is that researchers do not have control over the nature of the exposure in question and instead rely on the natural or unnatural circumstances that altered the nature of the exposure. In many cases, however, the conditions that change as a result of the natural experiment are multifaceted and related, making it difficult to tease apart the salient feature of the exposure. In this case, the authors are interested in the effects of proximity to food and recreational facilities. Yet it is likely that these characteristics are correlated with, and confounded by, other neighborhood characteristics like housing quality, violent crime, and healthcare access that may be related to the outcomes of interest. Indeed, this same natural experiment in Japan has previously been used to examine the effects of neighborhood social capital. 5 Although the theoretical links between cardiometabolic outcomes and the food and physical environment strengthen the conceptual basis for the current study, the selection of any particular neighborhood characteristic as the exposure of interest is nevertheless somewhat indiscriminate, such that the results cannot be construed as definitively implicating the effects of the proximity to the food and recreational facilities themselves. Once again, this is a challenge for the broader neighborhood-health literature, as neighborhood resources often tend to cluster together, making it challenging to disentangle the effects of one specific feature. Although this makes it difficult to advance theory on specific mechanisms through which neighborhoods may affect health, it is nevertheless reflective of the complexities of the real world in which individuals live. Relatedly, the …