Can discrete-time analyses be trusted for stepped wedge trials with continuous recruitment?
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arXiv
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| Autores principales: | , , , , |
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| Formato: | Preprint |
| Publicado: |
2025
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| _version_ | 1866917100419809280 |
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| author | Wang, Hao Tong, Guangyu Allore, Heather Taljaard, Monica Li, Fan |
| author_facet | Wang, Hao Tong, Guangyu Allore, Heather Taljaard, Monica Li, Fan |
| contents | In stepped wedge cluster randomized trials (SW-CRTs), interventions are sequentially rolled out to clusters over multiple periods. It is common practice to analyze SW-CRTs using discrete-time linear mixed models, in which measurements are considered to be taken at discrete time points. However, a recent systematic review found that 95.1\% of cross-sectional SW-CRTs recruit individuals continuously over time. Despite the high prevalence of designs with continuous recruitment, there has been limited guidance on how to draw model-robust inference when analyzing such SW-CRTs. In this article, we investigate through simulations the implications of using discrete-time linear mixed models in the case of continuous recruitment designs with a continuous outcome. First, in the data-generating process, we characterize continuous recruitment with a continuous-time exponential decay correlation structure in the presence or absence of a continuous period effect, addressing scenarios both with and without a random or exposure-time-dependent intervention effect. Then, we analyze the simulated data under three popular discrete-time working correlation structures: simple exchangeable, nested exchangeable, and discrete-time exponential decay, with a robust sandwich variance estimator. Our results demonstrate that discrete-time analysis often yields minimum bias, and the robust variance estimator with the Mancl and DeRouen correction consistently achieves nominal coverage and type I error rate. One important exception occurs when recruitment patterns vary systematically between control and intervention periods, where discrete-time analysis leads to slightly biased estimates. Finally, we illustrate these findings by reanalyzing a concluded SW-CRT. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2511_18731 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Can discrete-time analyses be trusted for stepped wedge trials with continuous recruitment? Wang, Hao Tong, Guangyu Allore, Heather Taljaard, Monica Li, Fan Methodology In stepped wedge cluster randomized trials (SW-CRTs), interventions are sequentially rolled out to clusters over multiple periods. It is common practice to analyze SW-CRTs using discrete-time linear mixed models, in which measurements are considered to be taken at discrete time points. However, a recent systematic review found that 95.1\% of cross-sectional SW-CRTs recruit individuals continuously over time. Despite the high prevalence of designs with continuous recruitment, there has been limited guidance on how to draw model-robust inference when analyzing such SW-CRTs. In this article, we investigate through simulations the implications of using discrete-time linear mixed models in the case of continuous recruitment designs with a continuous outcome. First, in the data-generating process, we characterize continuous recruitment with a continuous-time exponential decay correlation structure in the presence or absence of a continuous period effect, addressing scenarios both with and without a random or exposure-time-dependent intervention effect. Then, we analyze the simulated data under three popular discrete-time working correlation structures: simple exchangeable, nested exchangeable, and discrete-time exponential decay, with a robust sandwich variance estimator. Our results demonstrate that discrete-time analysis often yields minimum bias, and the robust variance estimator with the Mancl and DeRouen correction consistently achieves nominal coverage and type I error rate. One important exception occurs when recruitment patterns vary systematically between control and intervention periods, where discrete-time analysis leads to slightly biased estimates. Finally, we illustrate these findings by reanalyzing a concluded SW-CRT. |
| title | Can discrete-time analyses be trusted for stepped wedge trials with continuous recruitment? |
| topic | Methodology |
| url | https://arxiv.org/abs/2511.18731 |