Key result
Only ~0.3% of translational chronic stress studies base sample size on biologically meaningful effect sizes.
Why the study?
Because chronic variable stress procedures deliberately impose animal suffering, it was explored whether studies align with the Three Rs principle of Reduction by using a biologically meaningful effect size to determine sample size.
Systematic Review (n=385)
The vast majority of in vivo studies using chronic variable stress procedures fail to report a biologically meaningful effect size for sample size estimation, raising ethical concerns regarding the principle of Reduction.
Answers are grounded in this paper and cite their sources.
Few translational stress studies power samples on meaningful effects; challenges ethical reduction principles and demands better methodological reporting.
All in vivo studies using laboratory animals should be guided by the Three Rs: Replacement, Reduction and Refinement. The concept of Reduction is important in sample size estimation; the sample size used should allow the detection of a biologically meaningful effect size using appropriate statistical tests, but not at the expense of animal suffering. Because studies using chronic variable stress (CVS) procedures deliberately impose suffering, we reasoned that Three Rs principles would be a strong consideration in experimental design. To explore this, we conducted a systematic review of CVS studies to ask whether a biologically meaningful effect size was used to determine the sample size. Only one article in our sample of 385 reported doing this. Accordingly, it is questionable whether most of these studies align strongly with the principle of Reduction. While determining a biologically meaningful effect size is not always straightforward, we believe it is central to making biologically informed decisions about study design and interpretation, and we discuss possible ways forward.
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Jordan et al. (2024) conducted a systematic review in Translational chronic variable stress procedures in laboratory animals (n=385). Reporting of sample size calculation based on biologically meaningful effect size was evaluated on Proportion of articles reporting the use of a biologically meaningful effect size to determine sample size. Only 1 out of 385 (0.3%) translational studies using chronic variable stress procedures reported using a biologically meaningful effect size to determine their sample size.
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