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 Transcranial Direct Current Stimulation (tDCS) and Parkinson's Disease (NCT01100762), a na na study. The primary outcome is Stride Length.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01100762 |
| Phase | NA |
| Condition | Parkinson's Disease |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 10 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Maryland, Baltimore |
| Results posted | Yes |
2. Clinical Question
Population
People with Parkinson's disease. The registry record lists an enrollment of 10. It does not report further details about the participants in the primary outcome record.
Intervention
The study describes sessions involving tDCS, treadmill walking, and tDCS combined with treadmill walking. The registry intervention list uses the name Cranial Electric Stimulation (CES), while the study summary describes transcranial direct current stimulation (tDCS).
Comparator
The conditions are assessed within a single group across sessions, rather than in a randomized, parallel-group comparison. The registry record does not describe a separate control group.
Primary question
Does stride length change from before to immediately after each training session, and how do the changes across the described sessions compare? The registry record identifies stride length as the primary outcome but does not report numerical outcome results.
The study's broader stated question concerns whether stimulation can affect stepping and walking ability, including performance on a treadmill. The listed primary outcome narrows that question to stride length, measured in centimeters. The record describes assessment before and immediately after each session. It does not report a numerical estimate of change, uncertainty around an estimate, or a statistical test for the primary outcome.
Because the same group is described across the sessions, the question is not equivalent to asking whether a randomized treatment group did better than a concurrently followed control group. The sequence of conditions matters when interpreting any differences: a contrast across sessions could reflect the session condition, but also changes associated with time, repeated testing, or the order in which conditions were received. The record does not report an analysis that separates these possibilities. It therefore supports describing the study question and design, but not estimating from the registry record whether one condition changed stride length more than another.
3. Trial Design
The registry classifies this as a single-group study with an enrollment of 10 and a completed status. Allocation is listed as not applicable, and masking is listed as none. The record does not describe random assignment to different treatment groups or a separate control group. Its design is therefore best understood as a sequence of sessions in one group, not as a like-for-like comparison between independently assigned groups.
The study summary describes three sessions. In the first, participants were to be tested, receive tDCS, and be tested again. In the second, they were to be tested, walk on a treadmill, and be tested again. In the third, they were to be tested, walk on a treadmill while also receiving tDCS, and be tested at the end. The summary describes the sessions as 7 days apart. The arm description instead describes the later sessions as 7-10 days apart. This difference in the interval wording is present in the registry record.
The intervention list calls the stimulation device Cranial Electric Stimulation (CES), whereas the study summary describes tDCS. The arm description also uses the term tPCS. The record does not explain these differences in terminology, so the intervention labels should be read as recorded rather than treated as evidence that the terms are interchangeable.
The study began in 2010-01 and had a primary completion date of 2011-06. The registry record does not report a statistical analysis plan, a rationale for the enrollment, interim analyses, or details of how the order of sessions was selected. Those design details should not be inferred from the planned session sequence alone.
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.
Overall Study
| Stage | Single Group |
|---|---|
| STARTED | 10 |
| COMPLETED | 10 |
| NOT COMPLETED | 0 |
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 | Single Group |
|---|---|---|
| Participants analysed | 10 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 1 |
| Age, Categorical: >=65 years | Participants | 9 |
| Sex: Female, Male: Female | Participants | 3 |
| Sex: Female, Male: Male | Participants | 7 |
6. Primary Endpoint
The registry lists the primary outcome as Stride Length, measured over Data collection occurred before and immediately after each training session.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | cm |
| Endpoint classification | Continuous Endpoint |
The primary outcome is stride length, measured in centimeters. The record identifies the outcome as a continuous measure summarized by a mean and standard deviation. It says measurements were collected before and immediately after each training session. Stride length represents the distance covered by a step in the gait assessment; as a quantitative measure, it allows the recorded distance to be described across participants and assessment times.
In general, a continuous endpoint can retain more detail than a simple classification such as whether a participant did or did not meet a threshold. Reporting a mean can describe the group's central level, while a standard deviation describes how spread out individual measurements are around that mean. Neither statistic alone establishes whether a change is important to participants or exceeds ordinary measurement variability.
The registry record does not report a clinical threshold for meaningful change, the numerical means or standard deviations, or the number of participants contributing data at each assessment. It also does not report a numerical pre-session to post-session change. Without those results, the endpoint's name and measurement scale clarify what was intended to be assessed, but they do not establish the direction, magnitude, precision, or clinical relevance of any change.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a primary endpoint and describes when it was to be measured, but it does not report numerical results for stride length. It lists zero analyses. Consequently, no outcome estimate, interval of uncertainty, or test result can be interpreted from the record. The absence of a posted numerical result is not evidence that stride length stayed the same, nor does it establish that it changed.
The study's single-group structure also shapes what a comparison across sessions could mean. In general, repeated assessments in the same participants can account for some stable differences between people when within-person changes are analyzed. However, session-to-session contrasts can also be influenced by the order of conditions, practice with the assessment, changes over time, or other factors that vary across sessions. The record does not report an analysis addressing those possibilities. There is no randomized allocation or separate control group listed that would make a treatment contrast independent of the session sequence.
The registry describes stride length measurements before and immediately after each session, which could support an assessment of short-term change if the corresponding observations and analysis were reported. But the record does not provide the before-and-after values, a change estimate, the number of observations included, or a measure of uncertainty. It is therefore not possible to assess how consistent the measurements were across participants or how precisely any average change was estimated.
The record also does not report a threshold for judging the importance of a change in stride length. Even if an average change were available, statistical evidence and clinical importance would be separate questions. A confidence interval, in general, describes the range of estimates compatible with the data and the method's assumptions; it does not itself decide whether a change matters to patients. No such interval is reported for this primary outcome.
The listed enrollment and completed status describe the record's study-level information, not the amount of usable primary outcome data. The registry record does not state how many participants completed each session or contributed measurements at every time point. As a result, neither the completeness of outcome follow-up nor the degree to which missing observations might affect an estimate can be assessed.
Overall, the available record establishes what the study intended to measure and the broad sequence of conditions. It does not establish whether stride length changed after any session, whether changes differed across the sessions, or how precise any estimate might have been. Any interpretation that assigns a direction or size to an effect would go beyond the results reported in the registry record.
9. Statistical Methods Explained
The registry record describes a continuous primary outcome, stride length, with a mean and standard deviation as the stated summary statistics. It does not report a statistical method used to compare the measurements or any numerical analysis results. The explanations below are general guidance for reading this kind of design and outcome, not a description of methods confirmed as having been used in this study.
What does a mean describe?
For a continuous measure such as stride length, the mean gives a summary of the measured values' central level. It can be useful for describing the group, but it does not show how much participants differ from one another. A mean can also conceal varied individual patterns: some participants could have measurements that rise while others fall, even if the group average changes little. Individual values or other distribution summaries can help show that variation, but they are not reported for this endpoint in the registry record.
What does a standard deviation describe?
In general, a standard deviation describes the spread of observations around their mean. It is not the same as the standard error, which describes uncertainty in an estimated mean and depends on the amount of data used. A relatively broad spread can coexist with a precisely estimated mean when there are many observations, while a narrow spread does not by itself guarantee a precise estimate when the number of observations is small. The registry identifies standard deviation as the intended dispersion measure but does not report its value for stride length.
How could repeated measurements be compared?
In general, when the same participants are measured before and after a session, an analysis can focus on each participant's within-person change. This differs from treating the before-session and after-session measurements as if they came from unrelated groups. A paired analysis uses the fact that observations from the same person are related; the size and direction of that relationship can affect the uncertainty of the estimated average change. The registry record does not report whether a paired method was used, how changes were calculated, or whether any model accounted for measurements across all sessions.
A repeated-measures model can, in general, account for correlations among multiple observations from the same participant. Its choice depends on the study question, the pattern of measurements, and assumptions about the data. It may also require decisions about how to represent session, time, and their relationship. The record does not report a model specification or enough outcome data to determine which approach was used. No model should be attributed to the study based only on the described schedule.
What does a confidence interval add?
In general, a confidence interval communicates uncertainty around an estimate. It is useful alongside an estimated change because it indicates which values are reasonably compatible with the observed data under the method's assumptions. A narrow interval indicates greater precision than a wide one, but precision is not the same as clinical importance, and an interval does not correct for limitations in the design. The registry record does not report a confidence interval for stride length.
What can a p-value tell a reader?
In general, a p-value evaluates how unusual data at least as incompatible with a specified null hypothesis would be if that hypothesis and the analysis assumptions were true. It is not the probability that a treatment has no effect, and it does not measure the size or practical importance of a difference. A p-value is most informative when read with an effect estimate, its uncertainty, the design, and the analysis plan. No p-value or inferential test is reported for the primary outcome in the registry record.
How should the planning assumptions be read?
The record gives assumptions for a planning illustration: a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a stated fraction of the observed effect. It says that non-time-to-event planning values are participants per arm and that time-to-event values are total events. These are planning assumptions, not a report of the study's analysis or observed precision. The described study is single-group and does not list two randomized arms. The record does not report the illustration's resulting sample-size values or the observed effect used as its reference. Such planning values, when available, would not be observed power and would not replace the study's outcome results.
In general, over-dispersion means that variation in observed data is greater than a statistical model assumes. When that occurs, a model that ignores the extra variation can understate uncertainty and make results appear more precise than they are. The registry record does not report a model or a distributional assessment for the continuous stride-length endpoint, so there is no basis to say whether over-dispersion was assessed or relevant in the study's analysis.
The study's sequential conditions also matter for method choice. In general, if condition order is fixed, a difference between sessions cannot automatically be attributed to the condition alone. Repeated testing, practice, time, and possible carryover are potential design considerations; identifying them as possibilities does not establish that they affected these observations. The registry record does not report randomization of session order or an analysis of order effects.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists six outcome measures and identifies stride length as the primary outcome. It lists zero analyses. It does not report which outcomes were analyzed, whether any secondary outcomes were designated in advance, or how multiple statistical tests were handled. The record also does not provide numerical results for the primary endpoint.
In general, multiplicity arises when several outcomes, time points, or comparisons are tested. Conducting many tests can increase the chance of obtaining at least one apparently unusual result by chance. A prespecified primary outcome can help distinguish the main question from additional analyses, while a stated adjustment or a clear hierarchy of tests can explain how multiplicity was addressed. The registry record does not report such a procedure, so the handling of multiplicity is not reported in the registry record.
The record describes measurements before and immediately after each session, but it does not report the data available at each assessment, participant flow through the sessions, or reasons for missing measurements. It does not state whether the analysis used all enrolled participants, only those with complete measurements, or another analysis population. The enrollment figure and safety at-risk figures do not establish the number included in an efficacy analysis.
In general, missing outcome data can reduce precision and can bias a result if the likelihood of missingness is related to participants' measurements or other relevant factors. Statistical approaches to missing data rely on assumptions, which should be described alongside the analysis. No missing-data method or assumption is reported in the registry record. The extent and potential effect of missing primary outcome data therefore cannot be assessed from this record.
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 |
|---|---|---|---|
| Single Group | 0 | 10 | 0.0% |
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 |
|---|---|
| Single Group | 0 of 10 |
The safety record lists 10 participants at risk in the single group, with 0 participants affected by serious adverse events and 0 affected by other adverse events. No serious adverse event terms are listed. The death field is not reported in the registry record; it should not be read as a reported zero.
These figures describe the adverse-event information entered in the registry record. They do not establish that no events occurred outside the recorded reporting categories or during periods not covered by the safety data. The record does not describe how adverse events were collected, the observation period for safety outcomes, or the criteria used to classify events. It also does not provide event-level narratives or a comparison with a control group.
In general, a zero count in a small study does not prove that an event cannot occur or that a procedure is risk-free. It means that the registry lists no affected participants for the specified category in the reported group. The safety figures should therefore be read as descriptive registry entries, not as a precise estimate of risk or as a comparison of safety between treatments.
12. What the Result Does, and Does Not, Mean
The record establishes that a completed, single-group study was designed to examine stride length around sessions involving stimulation, treadmill walking, and their combination in people with Parkinson's disease. It identifies stride length as the primary outcome and specifies a before-and-immediately-after measurement schedule. Those details clarify the study question, but they are not outcome findings.
Numerical results for stride length are not reported in the registry record. A direction or magnitude of change cannot be stated, and the record does not allow an assessment of statistical precision. There is also no reported clinical threshold with which to judge whether a possible change would be meaningful. The described session sequence does not provide a randomized comparison against a separate control group, so any session differences would need cautious interpretation even if numerical results were available.
In general, a statistical association or change observed across assessments is not automatically proof that the session condition caused it. Design features, repeated measurement, session order, and the completeness of outcome data are relevant to causal interpretation. The registry record does not report analyses that address these issues. It also does not report sufficient information to determine whether the primary outcome was analyzed as planned or how any missing observations were handled.
The listed safety figures report no participants affected in the serious or other adverse-event categories, but the record does not supply enough detail to interpret those counts as a comprehensive assessment of safety. Likewise, the completed status does not substitute for numerical efficacy results.
The appropriate conclusion is limited: the record describes the intended clinical question and study structure, but it does not report results that establish whether stride length changed or whether one session condition differed from another. Any stronger claim about benefit, lack of benefit, or comparative effects would exceed what the registry record reports.
13. Why This Trial Matters Statistically
This study is statistically notable because its central question is framed around several conditions delivered to a single group over successive sessions. That structure differs from a randomized parallel-group trial. It makes within-person measurement potentially relevant, but it also means that condition and session sequence may be difficult to disentangle. The record describes the schedule but does not report an analysis addressing order or time.
The choice of stride length as a continuous primary outcome also illustrates why an endpoint definition is only part of a statistical result. To understand a change, readers would need an estimate, a measure of its uncertainty, information about how many observations contributed, and a clear account of how repeated measurements were analyzed. The registry record identifies the unit and summary form but does not report those outcome results.
The record's planning assumptions offer a further statistical distinction. A planning illustration based on a two-arm allocation and a fraction of an observed effect is not the same as an analysis of a single-group session sequence. Planning quantities describe assumptions used to explore study size; they do not show what the study found, how precise its observed data were, or the probability that its result is correct.
Finally, the absence of reported analyses and numerical primary outcome results limits what can be learned from the registry entry. This is not a finding of no effect. It is a limitation on what can be concluded from the posted record. Keeping that distinction clear prevents a study description, a safety count, or a planning assumption from being mistaken for evidence about the primary clinical outcome.
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 main limitation for interpreting this trial from the registry record is the absence of numerical results for the primary outcome. Means, standard deviations, changes, uncertainty estimates, and test results are not reported. Without them, the direction and precision of any stride-length change cannot be assessed.
The single-group design does not include a separate randomized control group in the registry description. The sessions are presented in a sequence, and the record does not say that their order was randomized. In general, when conditions occur in a fixed sequence, condition differences may be entangled with time, practice, or other session-related influences. This is a design consideration, not evidence that any one influence affected this study.
The interval between sessions is described differently in the study summary and the arm description: one states 7 days apart, while the other states 7-10 days apart. The registry also uses CES, tDCS, and tPCS terminology in different places and does not explain the differences. These inconsistencies make the exact description less clear, and should not be resolved by assuming details that are not reported.
The registry does not report participant-level outcome availability, the analysis population, missing-data handling, or reasons for any missing observations. It also does not report the statistical model, a method for handling multiple outcomes, or a clinical threshold for meaningful stride-length change. The safety entry provides counts but not collection methods or observation details. These omissions limit assessment of both the outcome analysis and the scope of safety reporting.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Transcranial Direct Current Stimulation (tDCS) and Parkinson's Disease — NCT01100762.
- Registry record last updated 2019-10-30; status last verified 2019-10.
- Results first posted 2012-05-07.
- 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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Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
The registry record describes a completed, single-group study of stimulation, treadmill walking, and the combination in people with Parkinson's disease. Enrollment is listed as 10, allocation as not applicable, and masking as none. Stride length, measured in centimeters and summarized by a mean and standard deviation, is the primary outcome; measurements were planned before and immediately after each session.
The record lists six outcome measures and zero analyses, but it does not report numerical results for stride length. It also does not report a statistical analysis plan, missing-data methods, or a clinical threshold for meaningful change. Safety entries list 0 participants affected by serious and other adverse events among 10 at risk; the death field is not reported in the registry record. The posted information describes the study question and design, but does not establish the direction, size, or precision of an outcome effect.