Statistical techniques applied to environmental health sciences

我们最近指导了几个项目的数据分析，主要涉及农业健康研究(AHS)的数据，这是一个来自爱荷华州和北卡罗来纳州的有执照的杀虫剂施用者(主要是农民)队列。 在第一个项目中，我们试图评估AHS中男性农民施用者的伤害死亡率是否与使用农药的做法有关。从1993年到2008年，我们在727,543人年的随访中观察到了338例伤害死亡。我们使用COX比例风险模型来研究致命性伤害与使用特定的杀虫剂、个人防护设备、特定类型的农业设备以及其他因素的关系。暴露信息是在登记时收集的，时间从死亡前1到15年。致命性伤害随着农民每年使用杀虫剂的天数增加而增加，随着使用耐化学物质手套的减少而减少。某些除草剂与致命伤害有关。我们认为这些联系值得进一步研究，特别是有了关于接触和死亡的时间关系的更好的数据，我们强调必须谨慎地解释这些结果。 有机磷杀虫剂(OP)是美国最常用的杀虫剂之一。在第二个项目中，我们描述了AHS中农民农药施用者使用有机磷农药的情况。为此，我们评估了701名农民施用者的一生使用OP的情况，这些农民被招募参加一项神经测试研究，增加了关于OP使用的信息。这个样本是在复杂的抽样设计中随机选择的，该设计对高度暴露的个人进行了过度抽样(基于通常的AHS数据)，并仅限于居住在四个临床地点150英里以内的个人。我们使用了经验抽样权重，因此我们的估计反映了符合神经学研究条件的所有3863名男性申请者的OP经验。马拉硫磷和毒死磷是最常用的有机磷农药。在AHS的15年病程中，OP的使用量有所下降。 另一个项目是探索AHS中男性私人施用者接触杀虫剂和抑郁之间的可能关系。我们使用逆概率加权来解释因缺失数据而导致的排除，并使用多分类Logistic回归来估计优势比。曾经使用过的熏蒸剂和几种单独的杀虫剂都与抑郁症有关。 使用AHS的数据，我们还研究了农业环境暴露是否会加剧哮喘。我们注意到哮喘与几种农业活动和曾经使用两种除草剂呈负相关，但没有正相关(哮喘和过敏病例的子集除外)。这些观察结果与容易恶化的哮喘病例倾向于避免暴露于引发症状的可能性是一致的。 最后一个项目使用了AHS的数据，调查了糖尿病与注册前曾使用过特定杀虫剂之间的可能关系。以年龄作为时间尺度，以糖尿病的诊断为关注事件，我们用Cox比例风险模型来估计风险比。曾经使用过五种杀虫剂(其中三种是有机磷)的农民妻子报告曾经混合或使用过杀虫剂，这与糖尿病有关。

We have recently guided the data analysis for several projects, primarily involving data from the Agricultural Health Study (AHS), a cohort of licensed pesticide applicators (mostly farmers) from Iowa and North Carolina. In the first project, we sought to assess whether injury mortality was associated with pesticide-use practices among male farmer applicators in the AHS. From 1993 to 2008, we observed 338 injury fatalities over 727,543 person-years of follow-up. We used Cox proportional hazards modeling to study the association of fatal injury with use of specific pesticides, personal protective equipment, specific types of farm equipment, and other factors. Exposure information was collected at enrollment, from 1 to 15 years preceding death. Fatal injury increased with the number of days per year that a farmer applied pesticides and decreased with use of chemical-resistant gloves. Certain herbicides were associated with fatal injury. We regard these associations as deserving of further study, especially with better data on the temporal relationship of exposure and death, and we emphasize that these results must be interpreted with caution. Organophosphorous insecticides (OPs) are among the most commonly used insecticides in the US. In the second project, we characterized the use of OPs among farmer pesticide applicators in the AHS. For this effort, we assessed lifetime use of OPs among 701 farmer applicators who were recruited for a neurological testing study with augmented informaton about OP use. This sample was randomly selected in complex sampling design that oversampled highly exposed individuals (based on the usual AHS data) and restricted to individuals residing within 150 miles of four clinical sites. We used empirical sampling weights so that our estimates reflect the OP experience of all 3863 male applicators eligible for the neurological study. Malathion and chlorpyriphos were the most commonly used OPs. OP use declined over the 15 year course of the AHS. Another project is probing a possible relationship between pesticide exposure and depression among male private applicators in the AHS. We used inverse probability weighting to account for exclusions due to missing data and polytomous logistic regression to estimate odds ratios. Ever use of fumigants as a class and several individual pesticides were associated with depression. Using data from the AHS, we have also studied whether farming exposures contribute to exacerbation of asthma. We noted inverse association of asthma with several farming activities and with ever use of two herbicides but no positive associations (except in a subset of cases with asthma and allergy). These observations are consistent with the possibility that asthma cases prone to exacerbation tend to avoid exposures that trigger symptoms. A last project using data from the AHS examined the possible relationship between diabetes and ever use of specific pesticides before enrollment. Using age as the time scale and diagnosis with diabetes as the event of interest, we fit Cox proportional hazards models to estimate hazard ratios. Ever use of five pesticides (three of them organophosphates) were associated with diabetes among farmers wives who reported ever mixing or applying pesticides.