Vestibular Rehabilitation and Otolith Dysfunction: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Vestibular Rehabilitation and Otolith Dysfunction (NCT02652442), a na na study. The primary outcome is Change in Static Subjective Visual Vertical (SVV).

2. Clinical Question

3. Trial Design

The registry record describes a completed, sequential study of centrifugation parameters. It lists enrollment as 6, phase as NA, allocation as NA, masking as none, and the model as sequential. The project was sponsored by the VA Office of Research and Development. The recorded study start was 2016-01-04, and primary completion was 2020-07-06.

The study’s stated purpose was to identify optimal stimulus parameters for off-axis rotation (centrifugation) in healthy participants. Three experiments were described: distance off-axis (3.5 versus 7 cm), duration (1 minute versus 3 minutes), and schedule (daily versus biweekly). The record characterizes the comparisons as within-subject: participants were tested systematically under different parameter settings. This differs from a randomized comparison in which separate groups are assigned to intervention and control conditions. The registry explicitly notes that the listed arms are not a like-for-like control comparison.

For the distance experiment, the record says participants were tested at 3.5 cm and then at 7.0 cm, both for 1 minute, after a two-week washout period. It also notes that six participants initiated testing at 3.5 cm for 1-minute duration, and one participant did not continue with the study. The available record does not establish how many participants contributed data to each of the other parameter comparisons or to the primary outcome analysis.

The record lists interventions for distance, duration, and schedule, but does not report the detailed analysis plan or the results for those comparisons. The sequential model and within-subject approach are important when interpreting the study: the comparisons concern parameter settings in the same participant framework, not treatment effects against an independent control group. Order, carryover, and incomplete participation may matter for interpreting such data, but the registry record does not describe how those issues were handled analytically.

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.

Centrifugation - Distance

Reasons for not completing this period:

Centrifugation - Duration

Centrifugation - Schedule

Analysis population for the primary outcome, as defined in the registry: The progression through the study is sequential with participants first being tested at 3.5 cm and then at 7.0 cm (both for 1 minute duration) after a two-week washout period. Six participants initiated study testing at 3.5 cm for 1- minute duration, but one participant did not continue with the study. Thus, that participants data are available for the dataset at Distance = 3.5 cm and Duration = 1 minute.

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 Change in Static Subjective Visual Vertical (SVV), measured over baseline, immediately after 5 sessions of OAR training (1 week).

The primary endpoint was change in static subjective visual vertical (SVV), measured in degrees. SVV assesses perceived vertical orientation and is influenced by otolith function, according to the registry description. During testing, a participant sits upright in a darkened room without other visual cues and adjusts a laser line until it is positioned as vertical. The starting position of the line is randomized. Participants use a track ball to make the adjustment.

Five trials are completed, and the software calculates the distance from true vertical for each trial. The average of those trials is used for data analysis. The endpoint is therefore a continuous measure: it can take values across a scale, rather than placing participants into categories such as improved or not improved. The registry specifies reporting the mean and standard deviation.

The stated timeframe is baseline and immediately after 5 sessions of off-axis rotation training over 1 week. Comparing measurements over time can describe whether the measured perception of vertical changed during the training period. In this study, the endpoint was selected because SVV reflects spatial perception and is influenced by otolith function, the function targeted by the project.

The registry record does not report the actual baseline or post-training means, standard deviations, or change estimates. Without those values, the direction, size, and precision of the primary endpoint result cannot be evaluated from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical methods described in the registry record are limited. It identifies a continuous primary measure, reports that the measure is summarized as a mean and standard deviation, and describes a sequential, within-subject study. It does not report the inferential procedure used to compare conditions, whether estimates were adjusted, or how uncertainty was quantified. The methods below explain general statistical concepts relevant to this design; they do not assert that a particular method was used in this study.

What does a mean and standard deviation describe?

For a continuous endpoint such as SVV in degrees, the mean describes the central average of the measured values. The standard deviation describes variation among those values. The mean alone does not show whether participants’ measurements were tightly clustered or widely dispersed. The standard deviation gives information about that spread, but it is not itself a measure of the precision of the mean. Precision also depends on the amount of usable information and on the analysis design.

The endpoint description says that five SVV trials are completed and their average is used for analysis. Averaging repeated trials can reduce the influence of trial-to-trial fluctuation on a participant’s measurement. However, the registry record does not report trial-level data, participant-level outcome summaries, or whether the analysis used only the participant averages described in the endpoint definition.

How does a within-subject comparison work?

In general, a within-subject design compares measurements or conditions within the same participants. Its analysis should account for the fact that measurements from one person are related to one another. Treating related measurements as though they came from unrelated people can misrepresent uncertainty. A paired analysis, for example, focuses on each participant’s difference between conditions; other repeated-measures approaches can model more than two conditions or additional structure. These are general examples only. The registry record does not report which method was used.

A within-subject design can be useful when participants vary substantially from one another, because each participant can serve as their own reference across conditions. But the design does not by itself ensure that the parameter conditions are comparable. If one condition consistently comes first, time or practice effects may be entangled with the condition contrast. A washout period may be intended to limit carryover, but the record does not report evidence that carryover was absent or a statistical method for assessing it. The distance sequence is described as 3.5 cm followed by 7.0 cm, after a two-week washout period.

What would uncertainty estimates add?

A point estimate, such as a mean change, gives a single summary of the observed data. A confidence interval would show uncertainty around that estimate under the chosen statistical model. A narrow interval generally indicates greater precision than a wide interval, although interpretation also depends on the endpoint and study context. A p-value, if reported, would describe how compatible the data are with a specified null model under the assumptions of the test. It would not describe the size or practical importance of a change. The registry record does not report confidence intervals or p-values for the primary endpoint.

For a small study, estimates can be especially sensitive to individual observations. That is a general statistical consideration, not a reported finding about this trial. Participant-level data, the analysis population, and measures of uncertainty would be needed to assess the influence of individual observations and the precision of the comparisons. Those details are not reported in the registry record.

How should the planning illustration be read?

The stated planning assumptions describe an illustration based on the observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is specified as a fraction of the observed effect. For time-to-event settings, the illustration refers to the total number of events; for other settings, it refers to participants per arm. These are planning assumptions, not a report of the trial’s design rationale, and the resulting sample-size values are not reported in the registry record.

A planning illustration asks what sample size might be needed under its stated assumptions for a chosen effect and power target. It is not observed power. Observed power is not a useful substitute for reporting the estimate and its uncertainty after data have been collected. In particular, a planning calculation based on an observed effect can reflect uncertainty in that effect estimate and should not be treated as a separate confirmation of a result. The registry record does not report the trial’s sample-size justification or whether these planning assumptions were part of the original design.

What is not specified?

The registry record does not report the statistical test or model, the handling of repeated observations, any covariate adjustment, the confidence level for intervals, or the method for handling missing outcomes. It also does not report an analysis population definition or whether analyses followed a prespecified statistical plan. These omissions prevent a detailed appraisal of the inferential methods. General principles about paired data and uncertainty can explain what would matter, but they cannot identify the method actually used or establish that its assumptions were met.

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("Centrifugation Distance - 3.5 cm", "Centrifugation Distance - 7.0 cm", "Centrifugation Duration - 1 Minute", "Centrifugation Duration - 3 Minutes", "Centrifugation Schedule - Daily", "Centrifugation Schedule - Biweekly")
n   <- c(6, 5, 6, 5, 5, 5)
m   <- c(0.69, 0.58, 0.69, 0.89, 0.89, 0.32)
sp  <- c(0.51, 1.47, 0.51, 1.14, 1.14, 1.22)
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  Centrifugation Distance - 3.5 cm  6  0.690  0.510  0.155  1.225
CARM  Centrifugation Distance - 7.0 cm  5  0.580  1.470  -1.245  2.405
CARM  Centrifugation Duration - 1 Minute  6  0.690  0.510  0.155  1.225
CARM  Centrifugation Duration - 3 Minutes  5  0.890  1.140  -0.525  2.305
CARM  Centrifugation Schedule - Daily  5  0.890  1.140  -0.525  2.305
CARM  Centrifugation Schedule - Biweekly  5  0.320  1.220  -1.195  1.835

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists one primary outcome measure and three analyses. It also describes three parameter experiments: distance, duration, and schedule. Looking across several comparisons can raise a multiplicity issue: when many hypotheses are examined, the chance of at least one apparently notable result can increase. Statistical approaches to multiplicity may include adjustment, hierarchical testing, or a clear distinction between confirmatory and exploratory questions. The registry record does not report whether any such approach was used, or how the three analyses relate to the three experiments.

The record does not report a statistical analysis plan, prespecified hypotheses for each parameter contrast, or whether the primary endpoint was analyzed separately for each experiment. It therefore does not allow readers to determine which comparisons were intended as confirmatory or whether the reported analysis accounted for multiple comparisons. The primary outcome values and inferential results are not reported in the registry record.

Missing-data handling is also not reported. The registry notes that six participants initiated testing at 3.5 cm for 1-minute duration and that one participant did not continue with the study. It does not state the reason, the measurements available from that participant, whether the participant contributed to any analysis, or how incomplete outcome data were handled. The number of participants contributing to each parameter comparison is not reported in the registry record.

The analysis population is not defined. The record does not say whether analyses included everyone who initiated testing, only participants who completed a particular comparison, or another group. In a within-subject design, the available paired measurements can affect which participants contribute to a contrast. Without a population definition and missing-data method, the scope of the estimated results cannot be assessed.

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 5% reporting threshold.

Most frequent non-serious adverse event terms

The registry lists serious adverse events separately from other adverse events for each displayed group. Serious adverse events affected 0 participants in each listed group. The listed groups are Centrifugation Distance - 3.5, Centrifugation Distance - 7.0, Centrifugation Duration - 3 Minutes, and Centrifugation Schedule - Biweekly. The registry lists 0 deaths in each of those groups, and no serious adverse-event terms are listed.

For other adverse events, the record lists 6 affected among 6 at risk for Centrifugation Distance - 3.5; 4 among 5 at risk for Centrifugation Distance - 7.0; 5 among 5 at risk for Centrifugation Duration - 3 Minutes; and 4 among 5 at risk for Centrifugation Schedule - Biweekly. These counts are reported as group-specific summaries. They should not be added across groups because the study uses within-subject comparisons and the same participant may appear in more than one parameter group.

The serious-event counts describe what was recorded in these groups; they do not establish that no adverse effects occurred. Other adverse events are listed, and the record does not provide their individual descriptions in the registry record used for this analysis. It also does not report event timing, attribution, severity beyond the serious/non-serious distinction, or a formal comparison of safety between settings. The counts should therefore be read as descriptive registry information, not as a causal or comparative safety analysis.

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

The study addresses a parameter-selection question: how distance, duration, and schedule of off-axis rotation relate to a measure of perceived vertical in healthy participants. Its design is described as sequential and within-subject, and its primary endpoint is static subjective visual vertical. These details explain the research question and the measurement strategy. They do not, on their own, indicate what the results were.

The registry record does not report the primary outcome values, changes from baseline, standard deviations, confidence intervals, or inferential results. As a result, it is not possible to state whether SVV changed, how large any change was, whether the changes differed across settings, or how precisely those comparisons were estimated. The stated aim of identifying optimal stimulus parameters is a purpose, not a reported finding.

The listed intervention contrasts are not randomized comparisons with an independent control group. Within-subject comparisons can address differences among conditions in the same participants, but sequence and time-related effects may complicate interpretation. The distance sequence and washout are described, but the record does not report analyses of order effects or carryover. The detailed procedures and results for the duration and schedule experiments are also not reported.

The project description refers to healthy participants, while the registry lists dizziness as a condition. The stated project purpose is to examine parameters for otolith dysfunction in healthy participants. The record does not report evidence that the findings, if available elsewhere, apply to people with a particular diagnosis or history. No clinical conclusion can be drawn from the registry entries alone.

The adverse-event counts show zero serious events in the listed groups and counts of other events as recorded. They do not describe whether an event was caused by centrifugation or whether risks differed between settings. Overall, the registry record establishes the study framework and outcome definition, but not the evidence needed to judge the size, precision, or clinical relevance of any outcome change.

14. Why This Trial Matters Statistically

This trial is statistically interesting because it compares parameter settings within participants rather than assigning independent groups to a treatment and control condition. This structure can make participant-level comparisons informative when individual baseline measurements vary. It also makes it important to recognize that observations from the same participant are related and should not be interpreted as independent group data.

The sequence matters as well. The distance comparison is described as testing 3.5 cm before 7.0 cm, with a two-week washout period. When conditions are ordered, condition effects can be difficult to separate from order, time, or practice effects unless the design or analysis addresses them. The record does not report whether these issues were evaluated, making this an important point for statistical interpretation rather than a basis for assuming a particular bias.

The study also illustrates the difference between a research aim and a reported result. Its objective was to identify optimal centrifugation parameters, and it specifies a continuous measure linked to spatial perception and otolith function. But the registry record does not report primary endpoint estimates or uncertainty. Without those, the statistical evidence for differences among settings cannot be assessed.

Finally, small enrollment and incomplete participation make clear reporting of the analysis population especially important. The record lists enrollment as 6 and notes that one participant did not continue after initiating a specified test sequence. It does not report how many participants contributed to each analysis or how missing observations were handled. These details matter for judging the precision and scope of within-subject comparisons. The record therefore offers a useful design description, while leaving central statistical results and methods unreported.

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 primary limitation for interpreting this record is that it does not report the primary outcome results. There are no reported mean SVV values, change estimates, standard deviations, confidence intervals, or test results. The direction, magnitude, and precision of the endpoint findings therefore cannot be assessed from the registry record.

The registry describes a sequential, within-subject structure and states that the distance testing proceeded from 3.5 cm to 7.0 cm, with a two-week washout period. It does not report whether condition order was randomized or counterbalanced, whether order and carryover effects were evaluated, or how repeated measurements were modeled. The record also does not explain how the washout period was selected or whether it was considered adequate.

Enrollment is listed as 6, and the record says that six participants initiated testing at 3.5 cm for 1-minute duration; one participant did not continue with the study. Reasons for discontinuation, available measurements, and the number included in each analysis are not reported. The analysis population and missing-data method are also not reported in the registry record. This limits assessment of how incomplete participation may have affected the comparisons.

Further limitations in the available record include the absence of a detailed statistical plan, inferential methods, multiplicity strategy, and outcome results for each parameter experiment. The registry lists three analyses, but does not explain their relationship to the three parameter experiments or whether any adjustment for multiple comparisons was made. The record identifies healthy participants as the target population for parameter testing, but does not provide enough information to assess participant characteristics or generalizability. These are limitations of what the registry record reports; they do not establish what may have been included in other study documents.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Vestibular Rehabilitation and Otolith Dysfunction — NCT02652442.
• Registry record last updated 2021-11-04; status last verified 2021-10.
• Results first posted 2021-11-04.
• 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

NCT02652442, titled “Vestibular Rehabilitation and Otolith Dysfunction,” is listed as completed and sequential, with enrollment of 6. The project aimed to identify centrifugation stimulus parameters in healthy participants. It describes within-subject comparisons of distance (3.5 versus 7 cm), duration (1 minute versus 3 minutes), and schedule (daily versus biweekly).

The primary endpoint was change in static subjective visual vertical, measured in degrees, from baseline to immediately after 5 sessions of training over 1 week. The registry describes the test procedure and specifies mean and standard deviation summaries, but does not report the primary outcome values or statistical comparison results. It also does not report the analysis population, missing-data method, inferential method, or multiplicity approach.

Serious adverse events affected 0 participants in each listed group, while other adverse events were reported in the group-specific counts. The record notes that one participant did not continue with the study after initiating distance testing at 3.5 cm for 1-minute duration. Without the endpoint estimates and analysis details, the registry record supports a description of study design and measurement, but not an assessment of the size or precision of the primary outcome findings.