Effects of Probiotics on Gut Microbiota, Endocannabinoid and Immune Activation and Symptoms of Fatigue in Dancers: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effects of Probiotics on Gut Microbiota, Endocannabinoid and Immune Activation and Symptoms of Fatigue in Dancers (NCT05567653), a randomized na study. The primary outcome is Qualitative Assessment of Intestinal Microbiota in Stool Samples.

2. Clinical Question

The registry record describes a study of probiotic supplementation in dancers, with a primary focus on the qualitative assessment of intestinal microbiota in stool samples. The broader planned research concerned gut-brain-axis elements, the endocannabinoid and immune systems, and symptoms such as fatigue.

3. Trial Design

This was a randomized, triple-masked, parallel-group trial listed as completed. Its phase is recorded as NA. The registry record gives enrollment as 26 and identifies Poznan University of Physical Education as the sponsor. The start date is 2022-10-01, and the primary completion date is 2023-03-08. These dates describe the trial record; they do not establish when each participant was enrolled or followed.

The two dietary-supplement interventions were the probiotic mix of Lactobacillus helveticus Rosell-52 and Bifidobacterium longum Rosell-175, and starch as placebo. The official title specifies 3-month supplementation. Although the arm descriptions state ca. 30 participants in each group, the overall recorded enrollment is 26. The actual number randomized to each group, and the reasons for any difference between the arm descriptions and enrollment, are not reported in the registry record.

Stool samples were collected at baseline and after the intervention according to the study protocol. The planned primary assessment was qualitative characterization of intestinal microbiota using shallow shotgun sequencing. That work was not carried out because funding and laboratory resources were lacking. Thus, the randomized design did not yield primary microbiota comparisons in the posted results.

The planned secondary measures included questionnaires about coping with stress, fatigue, gastrointestinal disorders, and sleep quality; body mass and body composition; diet composition assessed by food diaries; and a pain-threshold test. The record lists 26 outcome measures, but statistical analyses for these measures are not reported. Details such as the randomization procedure, masking roles, adherence procedures, and participant flow are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: Although 20 participants were randomized and assigned to groups (8 in PRO, 12 in PLA), only 17 completed the study. Three withdrew before receiving the intervention or failed to follow-up. The Protocol Enrollment field reflects only the final number analyzed per protocol.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Stool samples were collected at baseline and post-intervention according to the study protocol; however, the planned sequencing and metagenomic analyses were not performed due to lack of funding and laboratory resources. Consequently, no outcome data were generated for this Outcome Measure, no participants were analyzed (0 in each arm), and no statistical analyses were performed. No future analyses are planned for this Outcome Measure.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

Population: Randomization resulted in unequal group sizes due to participant withdrawal after allocation and scheduling constraints that prevented completion of baseline testing for several individuals. Consequently, baseline assessments were completed by 20 participants who met all inclusion criteria and provided valid baseline data used in demographic summaries.

6. Primary Endpoint

The registry lists the primary outcome as Qualitative Assessment of Intestinal Microbiota in Stool Samples, measured over Baseline and 3 months.

The primary endpoint was a qualitative assessment of intestinal microbiota in stool samples. The record states that gut-bacteria species were to be assessed using shallow shotgun sequencing, a next-generation sequencing method. Samples were collected at baseline and post-intervention, with the primary outcome timeframe stated as baseline and 3 months.

In general, a microbiota endpoint can describe which organisms are detected and how the composition of the microbial community is characterized. Repeated assessment can be used to examine changes over time, while a randomized comparator can help distinguish patterns associated with the intervention from patterns also seen in the comparison group. Those are general reasons for using such an endpoint, not findings from this trial.

Here, the intended sequencing and metagenomic analyses were not performed because of lack of funding and laboratory resources. The registry record explicitly says no outcome data were generated for this measure. Therefore, the endpoint has no reported estimate of change, group comparison, or uncertainty. The record does not establish whether the microbiota differed at baseline or changed during the study. The intended biological question remains unanswered by the primary outcome results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

General statistical explanation: a randomized parallel trial compares groups that are assigned to different interventions and followed over the same general study period. Random assignment is intended to make the groups comparable, on average, before treatment; the design does not guarantee that every relevant characteristic is balanced, especially in a small study. A comparison still requires observed outcomes and an analysis appropriate to the endpoint.

What does randomization contribute?

Randomization is useful because the assignment mechanism, rather than participant or investigator choice, determines group allocation. If assignment is implemented as intended and follow-up and measurement are sufficiently complete, a difference in outcomes between groups can be interpreted as an estimate of the intervention contrast under the analysis assumptions. This is a general explanation, not a claim that a particular randomization procedure was used in this trial. The procedure and allocation concealment details are not reported in the registry record.

The registry record identifies the study as randomized, triple-masked, and parallel. A parallel design means the intervention groups are treated as distinct groups for comparison rather than as sequential treatment periods in the same participants. The meaning of triple masking depends on which participant, investigator, or outcome-assessment roles were masked. Those roles are not reported, so the label cannot be translated into a more specific account of who knew assignments.

Why does an endpoint need an analysis?

An endpoint defines what is measured and when. The primary endpoint was qualitative assessment of intestinal microbiota in stool samples, with samples collected at baseline and post-intervention and a timeframe of baseline and 3 months. The planned sequencing method was shallow shotgun sequencing. To answer a treatment-comparison question, usable measurements would need to be generated and then compared between groups according to a stated analysis. In this case, the planned sequencing and metagenomic analyses were not performed, and no primary outcome data were generated. The endpoint definition alone cannot yield a result.

For a measured endpoint, an estimate describes the observed contrast or change, while a confidence interval describes the range of values compatible with the data and the analysis assumptions. A narrower interval generally indicates greater precision, and a wider interval indicates more uncertainty. These are general concepts. The registry record does not report a primary estimate or confidence interval for this endpoint, so precision cannot be assessed.

How should repeated measurements be understood?

When an outcome is measured at baseline and later follow-up, analysis can consider the starting measurement and the subsequent measurement, or examine change over time. The appropriate approach depends on the outcome scale, data structure, missingness, and prespecified analysis plan. A comparison of follow-up values without accounting for baseline may answer a different question from a model of change or an adjusted follow-up comparison. The statistical plan for this trial is not reported in the registry record. Since the planned microbiota data were not analyzed, no specific repeated-measures method can be attributed to the study.

Microbiota measurements may involve many organisms and features rather than a single simple numerical outcome. General statistical considerations can include how features are defined, how many are tested, how sparse measurements are handled, and how results are summarized. Those choices matter for interpretation and multiplicity. The record does not report completed sequencing analyses or their analytic choices, so it is not possible to assess how these issues would have been addressed.

What do the adverse-event counts communicate?

Counts at risk and counts affected are descriptive summaries. They report how many participants were included in the relevant safety accounting and how many had an event under the recorded definitions. In general, a zero count does not establish that the true risk is zero; interpretation depends on the size and completeness of the safety population, event definitions, and observation period. The record gives no further detail about those elements. The recorded figures should therefore be read as counts, not as a precise estimate of comparative safety.

The registry record reports zero analyses. It does not give a statistical analysis plan, model specification, handling of missing observations, or inferential results for the listed outcomes. No recalculated comparison is available from the posted outcome information, and no sample-size illustration can replace an observed endpoint analysis. General statistical methods can explain what an analysis would aim to do, but they cannot recover results that were never generated.

10. Multiplicity, Missing Data and Analysis Populations

The study listed 26 outcome measures, spanning biological assessments and questionnaire or physical measures. Testing many outcomes can increase the chance that some apparent differences arise by chance. General approaches to multiplicity include identifying a primary endpoint in advance, controlling the overall error rate across a family of tests, or treating secondary findings as exploratory. The statistical plan and any multiplicity adjustment are not reported in the registry record. In this trial, the primary microbiota analysis was not performed, and the record lists zero analyses, so there are no reported outcome tests for which an adjustment can be evaluated.

The record says stool samples were collected at baseline and post-intervention, but it does not give participant-level completeness or missing-data handling. It also does not provide a flow of participants from enrollment through assignment, follow-up, and analysis. The number randomized to each group and the number contributing to each planned secondary outcome are not reported in the registry record. The adverse-event at-risk counts are not enough to reconstruct that flow or the analysis population.

In general, missing data can affect both the precision and the validity of a comparison, depending on why observations are absent and how missingness is addressed. No imputation method, complete-case strategy, sensitivity analysis, or other missing-data procedure is reported. The analysis populations—such as whether participants would be analyzed according to randomized assignment—are also not reported in the registry record. These omissions limit assessment of how any future or secondary estimates should be interpreted.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The posted adverse-event figures record no serious adverse events in either group: 0 affected among 8 at risk in the probiotic treatment group, and 0 affected among 12 at risk in the placebo group. For other adverse events, the record likewise gives 0 affected among 8 at risk in the probiotic group and 0 among 12 at risk in the placebo group. Deaths are recorded as 0 in both groups.

These are counts as entered in the registry record. They do not show that the underlying event risk is zero, and they should not be treated as a precise comparison between groups. The record does not describe the adverse-event definitions, ascertainment procedures, observation period, or why the at-risk counts differ from the total enrollment. The actual number assigned to each group and the relationship between these safety populations and the full trial population are not reported in the registry record.

Accordingly, the safety figures are best read narrowly: no serious or other adverse events, and no deaths, were recorded among the listed at-risk participants. They do not resolve questions about uncommon events, completeness of event collection, or safety beyond the recorded participants and period.

12. What the Result Does, and Does Not, Mean

The record establishes that a randomized, triple-masked, parallel study of a probiotic mix and starch placebo was conducted with a recorded enrollment of 26 and marked completed. It also documents the intended primary question: whether intestinal microbiota, assessed in stool at baseline and after the intervention, could be characterized following the planned supplementation. The record states that stool samples were collected, but that the planned sequencing and metagenomic analyses were not performed because of lack of funding and laboratory resources.

As a result, the posted information does not establish whether the probiotic intervention changed the gut microbiota, whether the groups differed, or how precisely any such difference could be estimated. It also does not demonstrate that there was no effect. A missing analysis is not equivalent to an estimate near zero, and the lack of generated primary outcome data cannot be interpreted as evidence for or against the intended biological question.

The registry lists planned secondary measures involving stress coping, fatigue, gastrointestinal disorders, sleep quality, body mass, body composition, diet, and pain threshold. Their outcome results are not reported in the registry record. The entry therefore does not support conclusions about those measures either. The adverse-event record gives descriptive zero counts for the listed at-risk groups, but these counts do not answer the efficacy question and have limited context.

In general, a treatment comparison requires outcome data, a clearly described analysis, and an assessment of uncertainty. The trial design is relevant to how a comparison might be interpreted, but it cannot substitute for missing measurements. The appropriate reading is that the registry records a completed trial with a planned primary endpoint that was not analyzed, rather than a reported test of whether the intervention changed the endpoint.

13. Why This Trial Matters Statistically

This trial is statistically important as an example of the difference between a carefully stated research question and an answerable result. The record identifies a randomized comparison, names the probiotic and placebo interventions, specifies stool sampling at baseline and post-intervention, and describes the intended sequencing method. Yet the primary laboratory analyses were not carried out. Without the endpoint measurements and analysis, the planned comparison cannot yield an estimate, uncertainty interval, or evidence about the direction of change.

The distinction matters because study design and study findings are not interchangeable. Randomization and masking are design features intended to strengthen a comparison, while the endpoint data and statistical analysis provide the evidence needed to describe that comparison. A completed status does not by itself mean that every planned outcome was measured or analyzed. Here, the registry explicitly gives the reason primary data were not generated: lack of funding and laboratory resources.

The entry also illustrates why outcome lists should be interpreted cautiously. Many different biological and participant-reported measures were planned, but their presence in the record does not mean results exist for each. With 26 listed outcome measures and zero analyses, readers cannot assess multiplicity, missingness, or comparative effects from those measures. Transparent reporting of unperformed analyses is itself useful because it distinguishes unavailable evidence from a negative finding.

For clinical researchers and statisticians, this record underscores the importance of feasible laboratory plans, complete outcome reporting, and clear descriptions of analysis populations and methods. Those general considerations are relevant to interpreting the record, but the specific operational details beyond the stated funding and resource limitations are not reported.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The primary limitation is that the planned stool sequencing and metagenomic analyses were not performed, so no primary outcome data were generated. The registry record attributes this to lack of funding and laboratory resources. Sample collection alone cannot support a microbiota comparison; the planned measurements and analysis are absent.

The record lists enrollment of 26 but describes ca. 30 participants in each arm. Actual arm assignment counts, participant flow, and reasons for the difference between those descriptions are not reported in the registry record. The adverse-event populations include 8 participants at risk in the probiotic group and 12 in the placebo group, but the record does not explain how these counts relate to total enrollment or assignment.

The entry names 26 outcome measures and zero analyses. Results for the planned secondary measures are not reported in the registry record. Statistical methods, analysis populations, missing-data procedures, multiplicity handling, and outcome-specific participant counts are also not reported. These gaps prevent assessment of estimates, precision, and the potential influence of incomplete observations.

The record describes the study as triple-masked but does not specify which roles were masked. It also does not report the randomization procedure, adherence information, or detailed safety ascertainment. The completed status and recorded adverse-event counts should therefore be interpreted within the limits of the information documented in the registry record, rather than as a complete account of all trial procedures or outcomes.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Effects of Probiotics on Gut Microbiota, Endocannabinoid and Immune Activation and Symptoms of Fatigue in Dancers — NCT05567653.
• Registry record last updated 2026-02-20; status last verified 2026-02.
• Results first posted 2026-02-20.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

NCT05567653 is listed as a completed, randomized, triple-masked, parallel trial sponsored by Poznan University of Physical Education. The recorded enrollment is 26, with a start date of 2022-10-01 and a primary completion date of 2023-03-08. The intervention was Lactobacillus helveticus Rosell-52 and Bifidobacterium longum Rosell-175; starch was the placebo comparator.

The primary outcome was qualitative assessment of intestinal microbiota in stool at baseline and 3 months, planned using shallow shotgun sequencing. Stool samples were collected, but sequencing and metagenomic analyses were not performed because of lack of funding and laboratory resources, leaving no primary outcome data. The record lists 26 outcome measures and zero analyses. Adverse-event figures report zero serious events, zero other events, and zero deaths in the listed groups, with 8 and 12 participants at risk, respectively. Further analysis and participant-flow details are not reported in the registry record.