This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Impact of Passive Heat on Metabolic, Inflammatory and Vascular Health in Persons With Spinal Cord Injury (NCT04971408), a non-randomized na study. The primary outcome is Interleukin-6.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04971408 |
| Phase | NA |
| Condition | Spinal Cord Injury, Chronic Inflammation, Glucose Metabolism |
| Allocation | Non-Randomized |
| Design model | Crossover |
| Masking | None (open label) |
| Enrollment | 10 |
| Arms in the primary outcome | n/a |
| Lead sponsor | VA Office of Research and Development |
| Results posted | Yes |
2. Clinical Question
Population
People with spinal cord injury. The registry record lists an enrollment of 10 but does not further describe the primary-outcome population.
Intervention
Repeated passive heat stress, described as three sessions per week for eight weeks.
Comparator
A control period described as one passive heat stress visit followed by eight weeks without intervention, while participants continued their usual exercise habits. The record identifies the comparison as nonrandomized and not like-for-like.
Primary question
How does plasma interleukin-6 concentration change across the study’s stated timepoints of 0 weeks, 8 weeks, and 16 weeks in relation to the passive heat stress and control periods?
The study addresses whether repeated exposure to passive heat is associated with changes in an inflammatory marker in people with spinal cord injury. Its background describes chronic inflammation, vascular changes, and impaired glucose metabolism as health concerns in this population, and notes that exercise may be difficult to access for some people with spinal cord injury. The registry rationale says earlier work in this population investigated short-term exposure, whereas this study examined repeated bouts over a longer period.
The primary outcome is interleukin-6, measured as a plasma concentration. Other listed outcomes concern vascular function, glucose tolerance, and inflammatory markers. The registry record does not report numerical primary-outcome results, so the size, direction, and precision of any change cannot be assessed from the information recorded. The question is therefore about the study’s intended comparison and measurement, not a conclusion about whether passive heat stress changed interleukin-6.
3. Trial Design
The registry record describes a completed, nonrandomized study with a crossover model and no masking. Enrollment was 10. The study start date is 2022-07-01, and the primary completion date is 2024-06-30. The sponsor is the VA Office of Research and Development.
The control description is one passive heat stress visit followed by no intervention for eight weeks; participants were to continue their regular exercise habits as usual. The passive heat stress description says that, after the control arm, participants received passive heat stress three times per week for eight weeks. These are the sequences described in the record. It does not report whether participants were assigned to different sequences, how any sequence was determined, or whether a washout period was used.
Although the record labels the model as crossover, it explicitly cautions that the allocation was nonrandomized and that the arms are not a like-for-like control comparison. The lack of random allocation matters because the registry record does not establish that periods or conditions were assigned in a way that balances other influences on outcomes. No masking was used, so the record does not describe participants or study personnel as blinded to the intervention.
The study status is completed, but completion status alone does not provide outcome findings. The registry record does not report a protocol, a sample-size justification, or details of how the nonrandomized comparison was planned analytically. It lists one primary outcome and secondary outcomes, but the numerical outcome results and the methods used to estimate treatment-period differences 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: Each enrolled participant completed a time-control phase of 8 weeks prior to the passive heating intervention.
Control
| Stage | 8 Week Time-Control Phase, Then 8 Week Passive Heating Intervention |
|---|---|
| STARTED | 10 |
| COMPLETED | 10 |
| NOT COMPLETED | 0 |
Intervention
| Stage | 8 Week Time-Control Phase, Then 8 Week Passive Heating Intervention |
|---|---|
| STARTED | 10 |
| COMPLETED | 9 |
| NOT COMPLETED | 1 |
Reasons for not completing this period:
| Reason | 8 Week Time-Control Phase, Then 8 Week Passive Heating Intervention |
|---|---|
| Event unrelated to the study | 1 |
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.
| Characteristic | Unit | All Study Participants |
|---|---|---|
| Participants analysed | 10 | |
| Age, Continuous | years | 45 (SD 14) |
| Sex: Female, Male: Female | Participants | 2 |
| Sex: Female, Male: Male | Participants | 8 |
| Race/Ethnicity, Customized: Hispanic | Participants | 4 |
| Race/Ethnicity, Customized: White | Participants | 4 |
| Race/Ethnicity, Customized: Black | Participants | 2 |
| Years since injury | years | 9.2 (SD 10.5) |
| BMI in kg/m2 | kg/m2 | 28.0 (SD 3.0) |
6. Primary Endpoint
The registry lists the primary outcome as Interleukin-6, measured over change from 0 weeks to 8 weeks to 16 weeks.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | pg/ml |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is plasma interleukin-6 concentration, measured in pg/ml. The registry describes the endpoint as a mean and its dispersion as a standard deviation. It says the plasma concentration was determined using enzyme-linked immunosorbent assays. The stated timeframe is change from 0 weeks to 8 weeks to 16 weeks.
Interleukin-6 is included as an inflammatory measure. The study rationale identifies chronic inflammation as one of the health concerns motivating research in people with spinal cord injury, and the primary endpoint gives the study a defined laboratory measure with which to examine that concern. A concentration provides a quantitative outcome that can be compared across the stated measurement times.
In general, a mean describes the central level of measurements in a group, while a standard deviation describes how spread out individual measurements are around that mean. These summaries do not by themselves show whether a change is attributable to an intervention or how precisely a group difference has been estimated. For that, the analysis and its uncertainty would also matter. The registry record does not report the observed interleukin-6 means, standard deviations, estimated changes, confidence intervals, or statistical tests. Consequently, the recorded endpoint definition explains what was intended to be measured, but does not establish the size or direction of any result.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies interleukin-6 as the primary outcome and describes when it was to be measured. It does not report numerical results for that outcome. There is therefore no posted estimate of change in interleukin-6, no confidence interval, and no p-value to interpret. Neither the direction nor the magnitude of a primary-outcome finding can be established from the registry information.
The record lists 10 participants enrolled. That count describes enrollment, not necessarily the number with usable measurements at each timepoint. The number included in each outcome analysis, the extent of missing measurements, and any reasons for missing data are not reported in the registry record. Without those details, the amount of information contributing to any outcome estimate cannot be assessed.
The design also affects interpretation. The registry labels the study nonrandomized and specifically notes that the arms are not a like-for-like control comparison. In general, random assignment can help balance factors that might affect outcomes; without it, differences between periods or conditions may reflect other influences as well as the intervention. A crossover design can allow within-participant comparisons, but the record does not describe the assignment process, period effects, possible carryover, washout, or the model used to account for repeated measurements. It is not possible to tell from the record whether these issues were addressed in the analysis.
The stated measurement schedule spans 0 weeks, 8 weeks, and 16 weeks. Measurements taken from the same participant are generally related rather than independent. In general, an analysis of repeated observations should account for that relationship; treating related measurements as independent can misstate uncertainty. The registry record does not report the statistical method used for the primary outcome, so no particular repeated-measures method should be attributed to this study.
Interpretation should therefore remain limited to what the record documents: a completed nonrandomized crossover study, its stated intervention periods, and its intended outcomes. The record also lists safety counts, but those counts do not fill the gap in primary efficacy results. No conclusion about an interleukin-6 change, its precision, or its relation to the intervention can be drawn from the posted registry information.
9. Statistical Methods Explained
The registry describes the primary outcome as a mean continuous measure with standard deviation, but it does not report an analysis method or numerical outcome findings. The concepts below explain how such measures are commonly interpreted; they are general statistical explanations, not a description of unreported procedures in this study.
What does a mean describe?
For a continuous measurement such as a concentration, the mean is a way to represent the group’s central level. It is calculated from the individual observations included in the analysis. It can be useful for comparing groups or timepoints, but it does not show how similar or different the individual observations are. A mean can also be influenced by unusually high or low observations, so the distribution of measurements can matter.
What does a standard deviation describe?
A standard deviation describes the spread of observations around their mean. A smaller spread indicates that individual measurements are closer to the mean, while a larger spread indicates more variability. It is not the same as the uncertainty in the mean estimate. That uncertainty depends on the variability and the amount of information available. The registry record gives the intended dispersion measure but does not post the observed means or standard deviations for interleukin-6.
What would a confidence interval add?
In general, a confidence interval gives a range of values compatible with an estimate under the assumptions of the analysis. Its width communicates precision: a narrower interval generally indicates greater precision, while a wider interval indicates more uncertainty. A confidence interval is not a guarantee that the true value lies within that particular range. No confidence interval for the primary endpoint is reported in the registry record, so its precision cannot be assessed.
Why does the crossover structure matter?
In a crossover study, participants may contribute measurements under more than one condition or period. This can make comparisons within the same participant informative because stable characteristics of that participant are shared across periods. However, measurements from one participant are related, and the order of periods may matter. In general, crossover analyses may need to account for participant-level pairing, time or period effects, sequence, and possible carryover from an earlier condition. The registry record does not say how participants moved through the periods or whether these effects were assessed.
The registry identifies the allocation as nonrandomized and cautions that the arms are not a like-for-like control comparison. This limits how confidently a difference can be attributed to the intervention. A nonrandomized comparison may be affected by systematic differences in timing, participant behavior, or other factors. The record does not report an adjustment strategy or the covariates, if any, used in an analysis. It would therefore be inappropriate to describe a hypothetical adjusted or paired estimate as the study’s result.
How should repeated measurements be handled?
The primary timeframe includes 0 weeks, 8 weeks, and 16 weeks. In general, repeated observations on the same person are correlated. Statistical methods for repeated measures account for this dependence when estimating changes and their uncertainty. The method selected can affect the estimate and its standard error, particularly when observations are incomplete or the correlation structure is modeled differently. The method used for this endpoint is not reported in the registry record.
When a study has more than one outcome or measurement time, the chance of finding at least one apparently notable result can increase if many tests are conducted. In general, multiplicity procedures may control that risk, or investigators may designate a primary outcome in advance and interpret secondary findings as exploratory. The record identifies a primary outcome and lists secondary outcomes, but the approach to multiplicity is not reported.
The registry’s sample-size assumptions describe a planning illustration based on the observed effect, a two-sided significance level of 0.05, equal allocation, and a normal approximation. The record does not give the resulting planning values or a trial-specific sample-size justification. Such an illustration is not observed power and does not replace an analysis of the actual data. The statistical tests, missing-data methods, and analysis populations are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry identifies interleukin-6 as the primary outcome and lists secondary outcomes including maximal cutaneous vascular conductance, glucose tolerance, TNF-alpha, and interleukin-1ra. It also reports 8 outcome measures. Examining multiple outcomes or multiple timepoints can raise multiplicity concerns: in general, the more statistical comparisons made, the greater the chance of at least one result appearing notable by chance. The registry record does not report whether a multiplicity adjustment was planned or used, how the primary endpoint was prioritized in interpretation, or whether secondary analyses were designated as confirmatory or exploratory.
The primary outcome has measurements described across 0 weeks, 8 weeks, and 16 weeks. The statistical plan for those repeated observations is not reported. The record does not describe how incomplete measurements were handled, whether an analysis included all enrolled participants or a subset, or how the analysis population was defined. It also does not report the number of participants with available data at each timepoint.
These omissions matter because missing observations can affect both the estimated change and its precision, particularly if the reasons for missingness are related to participant characteristics or outcomes. In general, analysis populations and missing-data assumptions should be made explicit to clarify what information supports an estimate. The registry record does not provide those details, so the completeness and representativeness of the outcome data cannot be evaluated from the posted information.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Control | 0 | 10 | 0.0% |
| Passive Heating Intervention | 0 | 10 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Control | 0 of 10 |
| Passive Heating Intervention | 0 of 10 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Control | 0 of 10 |
| Passive Heating Intervention | 1 of 10 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Control | Passive Heating Intervention |
|---|---|---|---|
| Adverse events unrelated to the intervention | Skin and subcutaneous tissue disorders | 0 of 10 | 1 of 10 |
The registry records no serious adverse events among 10 participants at risk in the control group and none among 10 participants at risk in the passive heating intervention group. It records no deaths in either group. For other adverse events, it reports none among 10 participants at risk in the control group and one affected participant among 10 at risk in the passive heating intervention group.
These are counts recorded in the registry, not estimates of comparative risk. The record does not provide details about the nature, timing, severity, or attribution of the other event. It also does not provide a statistical comparison of adverse events between groups. With these details unavailable, the counts should be read descriptively and not as evidence that the groups had equivalent safety outcomes.
In general, an adverse-event count depends on how events were defined, sought, classified, and reported, as well as on the number of participants observed and the duration of observation. The registry record does not describe those procedures. The recorded figures therefore summarize the entries available in the registry, while leaving uncertainty about event characteristics and how completely events were captured.
12. What the Result Does, and Does Not, Mean
The registry record documents a completed study of repeated passive heat stress in people with spinal cord injury. It identifies interleukin-6 as the primary outcome and describes a control period and an intervention period. It also lists other outcomes and records adverse-event counts. These details describe the research question and its design; they do not provide a numerical estimate of the primary outcome.
The record does not report interleukin-6 results, confidence intervals, or statistical tests. It therefore cannot establish whether the measured concentration changed, how large any change was, or how precisely it was estimated. Completion of the study does not itself answer those questions. Nor can the listed safety counts establish a comparative safety profile, given the absence of detail about the other event and its assessment.
Even if outcome estimates were available, the nonrandomized allocation and the record’s explicit caution that the arms are not a like-for-like comparison would be important to interpretation. A difference between periods could have more than one explanation. The record does not describe the assignment process, potential period or carryover effects, or an analysis that addresses those issues. The planned crossover structure alone does not show that such factors were controlled.
In general, a registry entry is useful for understanding how a study was described and what outcomes were intended, but it is not a substitute for complete results and analysis details. The interpretation supported by this record is therefore limited: the study examined repeated passive heat exposure over eight weeks and specified inflammatory, metabolic, and vascular outcomes, but the posted information does not allow an assessment of the primary outcome’s findings or precision.
13. Why This Trial Matters Statistically
This study raises a statistical question that is especially important in small, repeated-measures research: how should observations from the same participant across different periods be compared? The crossover label indicates a design in which conditions or periods may be related within participants, but the registry record does not report the sequence assignment or analysis method. Those details are central to understanding what a comparison estimates.
The registry also flags a design constraint directly: allocation was nonrandomized, and the arms are not a like-for-like control comparison. This warning matters because a statistical contrast does not automatically isolate an intervention effect. Differences between periods can reflect time, behavior, or other influences. A clear account of allocation and analytic handling would be needed to judge how much those alternatives could affect an estimate.
The primary endpoint is a quantitative inflammatory measure, with repeated measurements across the stated timeframe. Reporting the estimated change alongside uncertainty would be important because a point estimate alone does not convey precision. For this record, no numerical primary outcome estimate or confidence interval is reported. The enrollment of 10 also makes transparent reporting of the analyzed sample and missing measurements particularly useful; those details are not reported in the registry record.
The trial is statistically informative as an example of why design labels and completion status are not enough to evaluate evidence. Allocation, repeated-measure handling, missingness, multiplicity, and uncertainty all shape interpretation. The registry record gives a research question and selected design details, but does not report the analyses needed to assess the primary result.
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 most consequential limitation for interpreting this study from the registry record is that numerical results for the primary endpoint are not reported. There are no posted interleukin-6 estimates, measures of uncertainty, or statistical tests. The record therefore does not support an assessment of the direction, magnitude, or precision of change.
The design is described as nonrandomized, and the record states that the arms are not a like-for-like control comparison. This limits causal interpretation. The record does not explain how participants entered the sequence, whether sequence order varied, or whether any washout period was used. It also does not report how period effects or possible carryover were considered.
Enrollment was 10, but the number contributing data to each endpoint and timepoint is not reported. The handling of missing observations, the analysis population, and the reasons for any missing data are also not reported in the registry record. These omissions prevent assessment of how complete the outcome data were.
The registry lists 8 outcome measures and several measurement times, but does not report a multiplicity plan or the methods used to analyze repeated observations. It also does not give a trial-specific sample-size justification. The planning illustration described in the record is not a substitute for that information and is not observed power. Finally, details about the single other adverse event recorded in the passive heating intervention group are not reported, limiting interpretation of the safety counts.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Impact of Passive Heat on Metabolic, Inflammatory and Vascular Health in Persons With Spinal Cord Injury — NCT04971408.
- Registry record last updated 2026-03-06; status last verified 2026-02.
- Results first posted 2026-03-06.
- 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.
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18. Record Summary
NCT04971408 is a completed, nonrandomized crossover study sponsored by the VA Office of Research and Development. The registry lists enrollment of 10, no masking, a control period involving one passive heat stress visit followed by eight weeks without intervention, and a passive heat stress period described as three sessions per week for eight weeks.
The primary outcome is plasma interleukin-6 concentration in pg/ml, measured by enzyme-linked immunosorbent assays, with a stated timeframe of 0 weeks, 8 weeks, and 16 weeks. The registry also lists secondary outcomes related to vascular function, glucose tolerance, and inflammation.
The record reports no serious adverse events or deaths in either group and one other adverse event in the passive heating intervention group. Numerical primary-outcome results, analysis methods, missing-data procedures, and analysis populations are not reported in the registry record. The record cautions that the nonrandomized arms are not a like-for-like control comparison.