Several methods have been used to assess the seasonality of health outcomes in epidemiological studies. However, little information is available on the methods to study the changes in seasonality before and after adjusting for environmental or other known seasonally varying factors. Such investigations will help us understand the role of these factors in seasonal variation in health outcomes and further identify currently unknown or unmeasured risk factors. This tutorial illustrates a statistical procedure for examining the seasonality of health outcomes and their changes, after adjusting for potential environmental drivers by assessing and comparing shape, timings and size. We recommend a three-step procedure, each carried out and compared before and after adjustment: (i) inspecting the fitted seasonal curve to determine the broad shape of seasonality; (ii) identifying the peak and trough of seasonality to determine the timings of seasonality; and (iii) estimating the peak-to-trough ratio and attributable fraction to measure the size of seasonality. Reporting changes in these features on adjusting for potential drivers allows readers to understand their role in seasonality and the nature of any residual seasonal pattern. Furthermore, the proposed approach can be extended to other health outcomes and environmental drivers.

中文翻译：

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评估季节性及其潜在驱动因素在环境流行病学中的作用：教程。

在流行病学研究中，已经使用了几种方法来评估健康结果的季节性。然而，关于在调整环境或其他已知的季节性变化因素之前和之后研究季节性变化的方法的信息很少。此类调查将帮助我们了解这些因素在健康结果的季节性变化中的作用，并进一步确定当前未知或未测量的风险因素。本教程说明了在通过评估和比较形状、时间和大小来调整潜在环境驱动因素后，检查健康结果的季节性及其变化的统计程序。我们建议采用三步程序，分别在调整前后进行和比较：(i) 检查拟合的季节性曲线以确定季节性的大致形状；(ii) 确定季节性的高峰和低谷以确定季节性的时间；(iii) 估计峰谷比和归因分数以衡量季节性的大小。报告这些特征在调整潜在驱动因素时的变化，使读者能够了解它们在季节性中的作用以及任何剩余季节性模式的性质。此外，建议的方法可以扩展到其他健康结果和环境驱动因素。报告这些特征在调整潜在驱动因素时的变化可以让读者了解它们在季节性中的作用以及任何剩余季节性模式的性质。此外，建议的方法可以扩展到其他健康结果和环境驱动因素。报告这些特征在调整潜在驱动因素时的变化，使读者能够了解它们在季节性中的作用以及任何剩余季节性模式的性质。此外，建议的方法可以扩展到其他健康结果和环境驱动因素。