Stepped wedge cluster randomized trials (SWCRTs) often face challenges with potential confounding by time trends. Traditional frequentist methods can fail to provide adequate coverage of the intervention's true effect using confidence intervals, whereas Bayesian approaches show potential for better coverage of intervention effects. However, Bayesian methods have seen limited development in SWCRTs. We propose two novel Bayesian hierarchical penalized spline models for SWCRTs. The first model is for SWCRTs involving many clusters and time periods, focusing on immediate intervention effects. To evaluate its efficacy, we compared this model to traditional frequentist methods. We further developed the model to estimate time-varying intervention effects. We conducted a comparative analysis of this Bayesian spline model against an existing Bayesian monotone effect curve model. The proposed models are applied in the Primary Palliative Care for Emergency Medicine stepped wedge trial to evaluate the effectiveness of primary palliative care intervention. Extensive simulations and a real-world application demonstrate the strengths of the proposed Bayesian models. The Bayesian immediate effect model consistently achieves near the frequentist nominal coverage probability for true intervention effect, providing more reliable interval estimations than traditional frequentist models, while maintaining high estimation accuracy. The proposed Bayesian time-varying effect model exhibits advancements over the existing Bayesian monotone effect curve model in terms of improved accuracy and reliability. To the best of our knowledge, this is the first development of Bayesian hierarchical spline modeling for SWCRTs. The proposed models offer an accurate and robust analysis of intervention effects. Their application could lead to effective adjustments in intervention strategies.

翻译：阶梯楔形整群随机试验（SWCRTs）常面临时间趋势潜在混杂的挑战。传统频率学派方法在提供干预真实效应置信区间时可能覆盖不足，而贝叶斯方法则显示出改善效应覆盖的潜力。然而，贝叶斯方法在SWCRTs中的发展有限。我们提出了两种用于SWCRTs的新型贝叶斯层次惩罚样条模型。第一种模型面向包含大量群组和时间段的SWCRTs，重点分析即时干预效应。为评估其效能，我们将该模型与传统频率学派方法进行了比较。我们进一步扩展该模型以估计时变干预效应，并将此贝叶斯样条模型与现有贝叶斯单调效应曲线模型进行了对比分析。所提模型应用于急诊医学初级姑息治疗阶梯楔形试验，以评估初级姑息治疗干预的有效性。大量模拟实验与真实世界应用验证了所提贝叶斯模型的优势。贝叶斯即时效应模型在保持高估计精度的同时，始终能达到接近频率学派名义覆盖概率的真实干预效应区间估计，比传统频率学派模型更可靠。所提贝叶斯时变效应模型在准确性和可靠性方面较现有贝叶斯单调效应曲线模型有显著提升。据我们所知，这是针对SWCRTs的贝叶斯层次样条建模首次发展。所提模型为干预效应分析提供了准确且稳健的方案，其应用可有效调整干预策略。