Spinal Excitation to Enhance Mobility: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Spinal Excitation to Enhance Mobility (NCT03667573), a randomized phase 1 study. The primary outcome is Walking Speed Change From Baseline.

2. Clinical Question

3. Trial Design

The registry describes a randomized, single-masked, parallel-group phase 1 trial with an enrollment of 23. Its title is “Spinal Excitation to Enhance Mobility,” and its official title is “Spinal Excitation to Enhance Mobility in Elderly Adults.” The listed sponsor is the VA Office of Research and Development. The record lists the study as completed, with a start date of 2018-12-17 and a primary completion date of 2021-08-18.

Four groups are represented in the posted primary results: tsDCS dosage A with textured insoles, dosage B with textured insoles, dosage A with smooth insoles, and dosage B with smooth insoles. The corresponding group sizes are 6, 5, 5, and 7. The registry uses a parallel model, meaning the results are organized by assigned group rather than as a crossover comparison. Details about the randomization procedure, allocation concealment, and which people were masked are not reported in the registry record. “Single-masked” is reported, but the masked party is not specified.

The primary endpoint is a continuous measure: mean change in walking speed, in meters/second. The registry says it was measured at session 2, 2 days after baseline. It also lists Prefrontal fNIRS Change From Baseline as a secondary outcome, but numerical results for that measure are not reported in the registry record. The record identifies no posted analyses. The planned analysis methods, analysis populations, and handling of participants who did not contribute outcome data are not reported in the registry record.

The group descriptions establish that both stimulation dosage and insole texture varied across the four combinations. They do not, by themselves, establish which contrasts were prespecified or how the study was intended to separate the contribution of each component. That comparison plan is 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: Participants were excluded if they had major health conditions that would affect their safety in the study and/or their ability to perform the study procedures (e.g., ability to walk independently). Other exclusion criteria were excessive body mass index, major somatosensory impairment of the feet, and use of medications affecting the central nervous system.

Overall Study

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.

6. Primary Endpoint

The registry lists the primary outcome as Walking Speed Change From Baseline, measured over Measured at session 2 (2 days after the baseline session).

The primary endpoint is change from baseline in walking speed, measured in meters/second. It represents the change in a participant’s fastest safe walking speed over a complex walking course between the baseline session and session 2. The registry places session 2 at 2 days after the baseline session.

Walking speed is a continuous measure: it can take a range of numerical values rather than being limited to categories such as improved or not improved. The registry reports a group mean change and a standard deviation for each combination of stimulation dosage and insole texture. The mean describes the group’s average observed change. The standard deviation describes how spread out individual changes were around that group mean; it is not the standard error of the mean and is not a confidence interval.

Using a change-from-baseline outcome places each follow-up value in relation to the participant’s baseline measurement. The endpoint therefore summarizes change over the interval specified in the record, rather than reporting only a follow-up walking speed. The registry does not provide individual baseline or follow-up values, a clinically meaningful threshold, or an explanation for selecting the complex walking course. Those details are not reported in the registry record.

The posted endpoint is an observed measure of walking performance under the study’s assessment conditions. By itself, it does not establish how durable any change might be, whether it translates to daily mobility, or whether one intervention combination caused a different change from another.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry reports a continuous primary endpoint summarized as a mean and standard deviation. A mean is the arithmetic average of the observed values in a group. For this trial, the values being summarized are participants’ changes from baseline in fastest safe walking speed on a complex walking course. A mean change indicates the direction and average size of the observed changes in that group, in meters/second. It does not show how every participant changed.

A standard deviation is a measure of the spread of observations around their mean. A larger standard deviation indicates greater dispersion among the observed participant values; it is not a measure of the average change itself. The standard deviation also is not a standard error, which concerns the sampling uncertainty of an estimate. Neither the mean nor the standard deviation alone describes the full shape of the data, and the registry does not post individual values or distributional summaries.

General statistical explanation: uncertainty can be expressed with a confidence interval around an estimate. A confidence interval reflects the range of values compatible with the data under the method used to construct it. It is not the same as the observed spread among participants. The registry record does not report confidence intervals for the primary group means or for differences between groups, so those intervals cannot be interpreted for this study.

To assess whether groups differ, an analysis would ordinarily estimate a between-group contrast and quantify its uncertainty. A contrast might compare one group with another or evaluate a planned pattern across the four combinations. The registry lists four group summaries but does not post those contrasts, a statistical test, p-values, or an analysis model. The analysis plan and the intended primary comparison are not reported in the registry record. Therefore, the descriptive means cannot be converted into a claim of statistical evidence for a difference.

The study is described as randomized and parallel. Random assignment is intended, in general, to support comparisons between groups by distributing participant characteristics across assignments, while a parallel design assigns participants to groups that are followed separately. Those general features do not reveal the details of how randomization was performed in this trial. The randomization method, allocation concealment, and identity of the masked party are not reported in the registry record. The “single-masked” label does not specify which participants or study personnel were masked.

There are four combinations of dosage and insole texture. General statistical explanation: when an intervention has more than one component, an analysis may examine individual components, interactions between components, or selected combinations. An interaction asks whether the effect associated with one component differs depending on the level of another component. The presence of four combinations makes such questions conceivable, but the registry does not report that any particular component or interaction analysis was planned or performed. No such result should be inferred from the four means alone.

The registry’s sample-size assumptions describe a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. These are planning assumptions, not results from the trial’s own design process. The registry record does not report a sample-size justification for the trial. Any sample-size illustration should be understood as a hypothetical planning exercise, not as observed power or as evidence that a comparison was adequately powered.

General statistical explanation: over-dispersion occurs when data vary more than a statistical model assumes. If present, it can make standard errors too small and confidence intervals too narrow when the model does not account for it. The primary outcome is continuous and reported with a standard deviation, but the registry record does not report a model, diagnostic assessment, or method for handling any unusual distribution or excess variation. It is therefore not possible to determine from the record whether over-dispersion was assessed or relevant to the analysis.

The record identifies no posted analyses. It does not report whether the primary endpoint was analyzed using an unadjusted or adjusted method, whether baseline values were included in a model, or how missing observations were handled. The group means and standard deviations remain useful descriptions of the posted results, but they do not replace a prespecified analysis and its uncertainty estimates.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("tsDCS Dosage A and Textured Insoles", "tsDCS Dosage B and Textured Insoles", "tsDCS Dosage A and Smooth Insoles", "tsDCS Dosage B and Smooth Insoles")
n   <- c(6, 5, 5, 7)
m   <- c(0.054, 0.078, 0.085, 0.039)
sp  <- c(0.054, 0.04, 0.04, 0.12)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  tsDCS Dosage A and Textured Insoles  6  0.054  0.054  -0.003  0.111
CARM  tsDCS Dosage B and Textured Insoles  5  0.078  0.040  0.028  0.128
CARM  tsDCS Dosage A and Smooth Insoles  5  0.085  0.040  0.035  0.135
CARM  tsDCS Dosage B and Smooth Insoles  7  0.039  0.120  -0.072  0.150

11. Multiplicity, Missing Data and Analysis Populations

The registry names one primary outcome, Walking Speed Change From Baseline, and one secondary outcome, Prefrontal fNIRS Change From Baseline. It lists no analyses. The record does not report how many statistical hypotheses were planned, whether multiple comparisons were intended among the four groups, or whether any adjustment for multiplicity was planned or performed. A multiplicity strategy is therefore not reported in the registry record.

General statistical explanation: when several outcomes or contrasts are tested, the chance of obtaining at least one apparently unusual result can increase. An analysis plan may address this by prioritizing a primary comparison, adjusting significance thresholds, or treating secondary analyses as exploratory. The registry record does not specify which approach, if any, applied to this study. The presence of four group summaries is not enough to determine the number or hierarchy of planned tests.

The posted primary results include a mean and standard deviation for each group, but the record does not describe missing outcome data, exclusions, or the analysis population. It does not state whether all randomized participants were included in the primary analysis, whether participants without a session 2 assessment were omitted, or whether missing values were imputed. These missing-data and analysis-population details are not reported in the registry record.

General statistical explanation: missing data can affect interpretation when the likelihood of having an observed outcome is related to participant characteristics or outcomes. The consequences depend on why observations are missing and on the analysis method. Without information about missingness and the analysis population, the impact of any missing data cannot be assessed from the posted results.

12. 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 adverse-event record lists 0 serious events and 0 other events in each of the four groups. The numbers at risk for serious and other events are 6 for dosage A with textured insoles, 5 for dosage B with textured insoles, 5 for dosage A with smooth insoles, and 7 for dosage B with smooth insoles. The record lists 0 deaths in each group.

These figures describe what was recorded for the listed groups and denominators. They do not establish that no event could occur, nor do they quantify the chance of an event beyond the observed participants and the reporting period. The registry does not provide event narratives, event definitions, or further details about safety monitoring in the record. No serious-event terms are listed.

General statistical explanation: when an event count is zero, the observed count is still based on a finite number of participants. A zero count is not equivalent to proof that the underlying event risk is zero. Because the group sizes are limited, the posted counts give only a narrow description of recorded events during the period captured by the registry. Follow-up duration for adverse-event collection is not reported in the registry record.

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

The posted results establish that the registry reports group-level mean changes in fastest safe walking speed for four combinations of tsDCS dosage and shoe-insole texture. The mean changes are 0.054 meters/second, 0.078 meters/second, 0.085 meters/second, and 0.039 meters/second in the group order listed in the primary results. Standard deviations and group sizes are also reported. These values describe the observed data at session 2, 2 days after baseline.

They do not establish that the groups differ. The registry record reports no statistical analyses, between-group estimates, confidence intervals, or p-values. The numerical differences among the group means are not, by themselves, evidence that the combinations have different effects. Nor do the results establish the separate contribution of stimulation dosage or insole texture, or whether those components interact.

The record also does not report a threshold for a clinically important change, participant-level outcomes, or longer-term primary walking-speed results. The observed group averages therefore cannot determine whether a change was meaningful for a particular participant or whether it persisted beyond the recorded assessment. A mean summarizes a group and can conceal variation in individual responses.

The trial’s randomized design is part of its record, but the details of randomization and masking are not reported. The posted numerical summaries alone do not show how missing outcomes were handled or which analysis population was used. The named secondary outcome, Prefrontal fNIRS Change From Baseline, has no numerical result reported in the registry record.

In short, these are descriptive primary-outcome results from a small, four-group study. They characterize the observed group means and variation but do not supply the inferential comparisons needed to determine the precision of differences or support conclusions about comparative effects. No medical conclusion should be drawn from these summaries alone.

14. Why This Trial Matters Statistically

This trial is statistically notable for presenting a continuous change outcome across four intervention combinations while posting descriptive group summaries without inferential analyses. The record makes it possible to see the mean change, standard deviation, and group size for each combination. It does not provide a contrast, confidence interval, or test to quantify how uncertain a difference between combinations would be.

That distinction matters in small randomized studies. Group means can vary because of intervention differences, participant-to-participant variation, or both. Standard deviations describe observed dispersion, but they do not quantify the uncertainty in a comparison. The group sizes—6, 5, 5, and 7—are essential context for reading the summaries, while the registry does not provide inferential estimates that would show the precision of the group results.

The four combinations also raise questions about the intended comparison. Readers might ask whether the central interest was dosage, texture, a particular combination, or an interaction between components. The registry record does not report the planned comparison or analysis model. Without that information, the four means should be treated as descriptive rather than as evidence for a particular component effect.

The study addresses walking performance and includes a named secondary measure of prefrontal fNIRS change, but that secondary result is not reported. The primary result is tied to one specified session, so its scope is limited to the assessment described in the registry. Details needed to assess missing data, multiplicity, and analysis populations are also absent from the record.

For biostatistical interpretation, the key lesson is to distinguish observed summaries from estimates of comparative effects. Reporting means and standard deviations is informative, but a reader also needs the analysis plan, contrast estimates, and uncertainty measures to understand the strength and precision of group comparisons.

15. 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 group sizes are 6, 5, 5, and 7, and the registry reports no inferential analyses for the primary outcome. The available summaries therefore do not quantify uncertainty around the group means or any between-group differences. The standard deviations provide information about observed participant-level spread, but they cannot establish the precision of a contrast.

The record does not report a planned primary comparison, analysis model, statistical test, adjustment for baseline values, or method for handling multiplicity. It also does not describe the analysis population, missing outcomes, exclusions, or imputation. These omissions limit assessment of how the posted summaries relate to the randomized groups and whether any potential missingness could influence interpretation.

The registry identifies four combinations of dosage and insole texture, but does not report the intended approach for distinguishing the components or assessing an interaction. Details of the randomization procedure, allocation concealment, and the party masked are likewise not reported in the registry record. The “single-masked” designation alone does not resolve who was masked.

The primary endpoint is measured at session 2, 2 days after baseline. Later primary walking-speed outcomes and a clinically meaningful threshold are not reported in the registry record. The record names a secondary outcome, but numerical results for it are not reported. Adverse-event follow-up details are also not reported, which limits interpretation of the zero event counts.

These are limitations of what can be concluded from the registry record; they do not establish that particular procedures were absent from the study itself. The record does not provide enough information to assess those procedures.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Spinal Excitation to Enhance Mobility — NCT03667573.
• Registry record last updated 2023-09-13; status last verified 2023-08.
• Results first posted 2023-07-28.
• 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.

19. Record Summary

The registry describes a completed, randomized, single-masked, parallel-group phase 1 trial with an enrollment of 23. It lists four combinations of tsDCS dosage A or B and textured or smooth shoe insoles. The primary endpoint is mean change from baseline in fastest safe walking speed over a complex walking course, assessed at session 2, 2 days after baseline.

Posted group means are 0.054, 0.078, 0.085, and 0.039 meters/second, with standard deviations of 0.054, 0.04, 0.04, and 0.12 and group sizes of 6, 5, 5, and 7, respectively. The registry lists 0 serious events, 0 other events, and 0 deaths in each group.

No statistical analyses or inferential comparisons are reported. Confidence intervals, p-values, missing-data methods, and analysis populations are not reported in the registry record. Prefrontal fNIRS Change From Baseline is named as a secondary outcome, but its numerical result is not reported.