Comment on “Sub-anesthetic Xenon Increases Erythropoietin Levels in Humans: A Randomized Controlled Trial”
Sports Med
Comment on ''Sub-anesthetic Xenon Increases Erythropoietin Levels in Humans: A Randomized Controlled Trial''
Anoop Balachandran 0 1 2 3
David L. Streiner 0 1 2 3
Joseph F. Signorile 0 1 2 3
Dear Editor 0 1 2 3
0 Department of Psychiatry, University of Toronto , Toronto, ON , USA
1 & Anoop Balachandran
2 Department of Psychiatry and Behavioral Neurosciences, McMaster University , Hamilton, ON , USA
3 Laboratory of Neuromuscular Research and Active Aging, University of Miami , Coral Gables, FL , USA
-
This letter is in regard to the study titled ??Sub-anesthetic
Xenon Increases Erythropoietin Levels in Humans: A
Randomized Controlled Trial?? published recently in Sports
Medicine [
1
]. This is the first study to look at an important
question regarding the effects of xenon on circulating
levels of erythropoietin (EPO) in healthy humans. As stated
in the introduction of the paper, EPO has long been
established as a potent performance enhancing substance
[
2
]. As such, the study results could have considerable
implications in the sports performance area.
The study randomly assigned 24 subjects to either xenon
breathing or control gas breathing for 45 min. The primary
outcome measure was EPO levels in the blood. After 5 days
of data collection, the study concluded that xenon increases
EPO levels in humans, as evident in the title. However, the
reported statistical analysis does not warrant this conclusion.
Although it is reported under ??Statistical Analysis?? that
??single measurements were compared between the groups
at single time-points using Student?s t test (two groups) in
accordance with our statistician?s advice,?? only
withingroup or change from baseline score analysis is reported in
the paper. Therefore, the conclusion of xenon being
effective appears to be based on comparing a significant
withingroup change observed in the xenon group to a
non-significant change in the control group. Using simulated data,
Bland and Altman have elegantly shown that the practice of
comparing within-group p values is conceptually wrong,
invalid, and highly misleading [
3
]. If superiority is to be
claimed in a trial, statistical tests that compare
betweengroup mean differences should be conducted; that is, a
group-by-time analysis of variance or a two-sample t test.
In summary, the current conclusion of xenon increases
EPO levels in humans is inappropriate and possibly
misleading. We highly recommend authors conducting
randomized controlled trials compare outcomes using
between-group rather than within-group or tests against
baseline methods.
Compliance with Ethical Standards
Anoop Balachandran, David Streiner, and Joseph Signorile declare that
they have no conflict of interest relevant to the content of this letter. No
financial support was received for the preparation of this letter.
1. Stoppe C , Ney J , Brenke M , et al. Sub-anesthetic xenon increases erythropoietin levels in humans: a randomized controlled trial . Sports Med . 2016 ; 46 ( 11 ): 1753 - 66 .
2. Momaya A , Fawal M , Estes R . Performance-enhancing substances in sports: a review of the literature . Sports Med . 2015 ; 45 ( 4 ): 517 - 31 .
3. Bland JM , Altman DG . Comparisons against baseline within randomised groups are often used and can be highly misleading . Trials . 2011 ; 12 : 264 - 6215 -12-264. (...truncated)