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 Spinal Cord Stimulation to Treat Hypertension (NCT02828436), a randomized na study. The primary outcome is Change in Exercise Pressor Reflex From Baseline.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02828436 |
| Phase | NA |
| Condition | Hypertension |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | None (open label) |
| Enrollment | 9 |
| Arms in the primary outcome | 2 |
| Lead sponsor | University of Minnesota |
| Results posted | Yes |
2. Clinical Question
Population
The registry summary describes postmenopausal women with hypertension in its question about blood-pressure responses during lower-extremity dynamic exercise. It also describes women and men with hypertension in its question about whether lumbar epidural spinal cord stimulation changes blood pressure during exercise. The recorded endpoint population is not specified, so the posted results cannot be assigned confidently to either of those descriptions.
Intervention
The intervention of interest is spinal cord stimulation using the Boston Scientific Precision Spectra System. The registry describes stimulation as a way to investigate exercise-related afferent feedback and blood-pressure response. It does not report enough detail to establish how stimulation was delivered or how treatment periods were conducted.
Comparator
The other listed arm is Exercise Intervention. Its description says that a subject unable to tolerate spinal cord stimulation would be assigned to that arm. This makes the practical assignment rule difficult to reconcile with the registry’s randomized, crossover design labels. The record does not explain the relationship between those descriptions.
Primary question
The primary endpoint is change in the exercise pressor reflex from baseline, described as change in blood pressure during exercise and measured in mmHG. The research question is whether the recorded exercise-related blood-pressure change differs with spinal cord stimulation compared with the exercise intervention. The registry does not report an estimable statistical comparison answering that question.
3. Trial Design
The record describes a randomized trial with no masking and a crossover model. It lists two interventions: the Precision Spectra System, a device, and an exercise intervention, a behavioral intervention. The arm descriptions identify the spinal cord stimulation arm with the Boston Scientific Precision Spectra System. They describe the exercise arm as the assignment for a subject who cannot tolerate spinal cord stimulation.
Those descriptions do not make the trial structure fully clear. A crossover design generally entails participants receiving more than one condition in an ordered sequence, while the exercise-arm description sounds like an alternative assignment based on tolerability. The registry record does not report the treatment sequence, period structure, washout, or how the stated randomization relates to that assignment rule. It is therefore not possible to establish whether the posted arm results represent separate groups, treatment periods, or another arrangement.
Enrollment is recorded as 9. The posted primary-outcome arms report 1 participant in the spinal cord stimulation arm and 5 in the exercise intervention arm. The record does not explain how those endpoint counts relate to total enrollment. The study is marked completed, with a start date of 2017-03-22 and primary completion date of 2019-09-01. The phase is listed as NA, and the sponsor is the University of Minnesota.
The stated study aims concern blood-pressure response during lower-extremity dynamic exercise and whether lumbar epidural stimulation reduces that response in people with hypertension. The registry does not report enough design detail to determine exactly which participants contributed to each endpoint result or how within-participant observations, if any, were handled.
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.
Period 1
| Stage | Spinal Cord Stimulation | Exercise Intervention |
|---|---|---|
| STARTED | 0 | 9 |
| COMPLETED | 0 | 5 |
| NOT COMPLETED | 0 | 4 |
Reasons for not completing this period:
| Reason | Spinal Cord Stimulation | Exercise Intervention |
|---|---|---|
| Did Not Meet Inclusion Criteria | 0 | 3 |
| Lost to Follow-up | 0 | 1 |
Period 2
| Stage | Spinal Cord Stimulation | Exercise Intervention |
|---|---|---|
| STARTED | 9 | 0 |
| COMPLETED | 1 | 0 |
| NOT COMPLETED | 8 | 0 |
Reasons for not completing this period:
| Reason | Spinal Cord Stimulation | Exercise Intervention |
|---|---|---|
| Withdrawal by Subject | 4 | 0 |
| Did Not Meet Inclusion Criteria | 3 | 0 |
| Lost to Follow-up | 1 | 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.
Population: Only participants who completed the study are included in the baseline analysis.
| Characteristic | Unit | All Participants |
|---|---|---|
| Participants analysed | 5 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 2 |
| Age, Categorical: >=65 years | Participants | 3 |
| Age, Continuous | years | 62.6 (SD 10.6) |
| Sex: Female, Male: Female | Participants | 4 |
| Sex: Female, Male: Male | Participants | 1 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 1 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 |
| Race (NIH/OMB): White | Participants | 4 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Region of Enrollment: United States | participants | 5 |
6. Primary Endpoint
The registry lists the primary outcome as Change in Exercise Pressor Reflex From Baseline, measured over 2 years.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Error |
| Unit | mmHG |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is “Change in Exercise Pressor Reflex From Baseline.” It is a continuous measure, reported as a mean, with units of mmHG. Its description defines it as change in blood pressure during exercise, and its listed timeframe is 2 years. The registry does not clarify the measurement schedule or how the listed timeframe relates to each participant’s endpoint measurement.
Blood pressure during exercise is relevant to the stated research question because the study aims to characterize the exercise pressor response in people with hypertension and assess the response during spinal cord stimulation. A change-from-baseline endpoint expresses an outcome relative to a participant’s baseline measurement. In general, this can help describe how a measure changes over an intervention period, but interpretation depends on how baseline and follow-up measurements were obtained and analyzed. Those details are not reported in the registry record.
The posted means are 8.67 for spinal cord stimulation, based on 1 participant, and 16.29 for the exercise intervention, based on 5 participants. A standard error of 1.82 is reported for the exercise intervention mean; no spread estimate is posted for the spinal cord stimulation mean. These are arm-level summaries, not an estimated treatment contrast. The registry record says values are missing or not estimable for a two-arm comparison of this continuous endpoint, so the means alone do not establish a comparative effect.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted primary-outcome results are limited to descriptive summaries. The spinal cord stimulation arm has a reported mean change of 8.67, with 1 participant. The exercise intervention arm has a reported mean change of 16.29, with 5 participants, and a standard error of 1.82. The registry does not report an estimable two-arm comparison, and it posts no analyses. Thus, the arm means should not be read as a tested difference or as evidence that one intervention produced a greater or smaller response.
The precision of the summaries is also limited. The spinal cord stimulation result is based on a single participant, and no standard error or other spread estimate is reported for that arm. The exercise intervention standard error describes uncertainty around its mean under the assumptions of the calculation; it does not describe the range of individual participant responses. With no reported confidence interval or inferential analysis, the precision of a contrast between arms cannot be assessed from the registry record.
The reported endpoint counts do not account for all of the recorded enrollment, and the record does not explain that difference. It also does not identify the analysis population or clarify how the randomized crossover designation relates to the arm descriptions. This matters because a crossover study may require an analysis that uses within-participant comparisons, whereas a parallel-arm analysis compares distinct groups. The record does not say which approach was used or whether the posted summaries represent periods, participants, or another unit of analysis.
The registry describes the work as a pilot study, but it does not report a statistical analysis plan, a sample-size justification, or inferential results. The available figures therefore support a narrow description: the registry reports these arm-level means and counts for the named endpoint. They do not resolve the study’s intended comparative question. No conclusion about the size, direction, or statistical uncertainty of a treatment contrast can be drawn from the posted results alone.
9. Statistical Methods Explained
What does a mean describe?
In general, the mean is a summary of the measured values in a group. For a continuous endpoint such as change in blood pressure, it provides a central value in the endpoint’s stated units. It does not show how widely individual observations are distributed, whether there are unusual values, or whether participant responses were similar. Those questions require information about variability and the underlying observations.
The registry reports a mean for each arm. It reports a standard error for the exercise intervention arm, but not for the spinal cord stimulation arm. In general, a standard error describes the precision of an estimated mean, conditional on the data and statistical assumptions. It is not the same as a standard deviation: a standard deviation describes spread among individual observations, while a standard error concerns uncertainty in an estimate of the mean. With only 1 participant reported in the spinal cord stimulation arm, the record offers no posted spread estimate for that arm.
Why is a treatment contrast different from two arm means?
In general, a comparative treatment effect is an estimate of the difference between conditions, with a measure of its uncertainty. Arm means are inputs to such a comparison, but they do not by themselves provide the comparison’s standard error, confidence interval, or test result. The registry explicitly notes that values are missing or not estimable for a two-arm comparison of this continuous endpoint. It posts no analysis result, such as a confidence interval or p-value, for the primary outcome. The arm-level summaries should therefore remain descriptive.
A confidence interval, in general, gives a range of values compatible with a statistical estimate under a specified method and assumptions. Its width conveys precision: a wider interval indicates less precise estimation than a narrower interval. No confidence interval for the primary treatment contrast is reported. It would not be appropriate to reconstruct one without the necessary design and analysis information, particularly because the record identifies a crossover model but does not describe the participant-level data or analysis.
Why does the crossover label matter?
In general, crossover trials can compare conditions within the same participant. Such an analysis must account for the fact that observations from the same participant are related rather than independent. The treatment sequence, period, and any carryover effects may also matter to interpretation. These are general design considerations, not claims about what occurred in this study. The registry record does not report the sequence, treatment periods, washout, or an analysis accounting for repeated measurements.
The arm description creates additional uncertainty: it says that a participant unable to tolerate spinal cord stimulation would be assigned to the exercise intervention arm. The record does not explain how that rule fits the randomized crossover designation. Without clarification, the analysis unit and comparison structure cannot be established from the registration information.
What do the planning assumptions mean?
The record describes a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says that the target effect is a stated fraction of the observed effect. These are assumptions for a planning exercise, not a report of the trial’s original design or an observed measure of statistical power. The registry does not report the trial’s own sample-size justification, and the primary comparison is not estimable in the posted results. Consequently, the illustration cannot substitute for a formal analysis of the trial.
In general, a sample-size calculation asks how many participants would be needed to detect a specified effect under chosen assumptions. The answer depends on the target effect, variability, allocation, significance level, and analysis method. A planning calculation based on an observed effect is especially dependent on the estimate used as its starting point. It should not be interpreted as evidence that a completed study had adequate power, nor as proof that a result is meaningful or not meaningful. No numerical sample-size results are stated in the registry record.
Why can over-dispersion matter?
In general, over-dispersion means that the observed variability is greater than a statistical model expects. It can make standard errors too small if the model does not allow for that extra variability, which can make uncertainty appear narrower than it is. This concept is most relevant when the outcome and model have a variance structure that can be compared with a model assumption. The posted primary endpoint is continuous, but no fitted model or variance assessment is reported, so there is no basis to say whether over-dispersion was assessed or present in this study.
More broadly, the registry does not report an inferential method for the endpoint. It does not identify adjustment variables, a repeated-measures model, a crossover-specific comparison, or a method for handling incomplete observations. General statistical explanations cannot establish which approach the investigators used. The posted means and standard error are insufficient to recreate an analysis that accounts for the registered design.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one primary outcome measure and no posted secondary outcomes. It reports no analyses. A multiplicity adjustment is not described, and the record does not report whether additional outcomes or comparisons were prespecified outside the posted results. In general, when multiple hypotheses are tested, the chance of at least one false-positive result can increase; statistical plans may address that issue by defining a primary comparison or using an adjustment. The record does not state whether any such plan was used.
Missing-data handling is not reported in the registry record. The endpoint results list 1 participant for spinal cord stimulation and 5 for the exercise intervention, while total enrollment is 9. The record does not explain the endpoint counts, identify exclusions, or say whether observations were unavailable, not collected, or not estimable. These possibilities should not be inferred from the difference in counts alone.
The endpoint population is blank, and the analysis population is not specified. The record does not say whether participants were analyzed according to randomized assignment, treatment received, completed treatment periods, or another rule. This is particularly relevant given the crossover designation and the arm description based on stimulation tolerability. No statistical plan or sensitivity analysis is reported, so the effects of missing observations and analysis-population choices cannot be evaluated.
The planning illustration uses stated assumptions, including a two-sided significance level of 0.05, but it is not a report of the trial’s actual sample-size justification. The registry does not report the protocol’s approach to multiplicity, missing data, or analysis populations.
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 |
|---|---|---|---|
| Spinal Cord Stimulation | 0 | 1 | 0.0% |
| Exercise Intervention | 0 | 5 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Spinal Cord Stimulation | 0 of 1 |
| Exercise Intervention | 0 of 5 |
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 |
|---|---|
| Spinal Cord Stimulation | 0 of 1 |
| Exercise Intervention | 0 of 5 |
The registry reports serious adverse event figures for the two listed groups. In the spinal cord stimulation group, 1 participant was at risk, 0 had a serious adverse event, and 0 deaths were recorded. In the exercise intervention group, 5 participants were at risk, 0 had a serious adverse event, and 0 deaths were recorded. The record also reports 0 other adverse events among 1 participant at risk in the spinal cord stimulation group and 0 among 5 at risk in the exercise intervention group.
These counts describe the safety information posted for the recorded groups. They do not establish that no adverse events could occur, and the small numbers at risk limit how much can be learned about uncommon events. The registry does not report additional serious-event terms. It also does not explain how the adverse-event groups relate to the crossover designation, treatment periods, or the total enrollment. The figures should therefore be read as the recorded counts, not as a comprehensive estimate of risk or a comparative safety analysis.
12. What the Result Does, and Does Not, Mean
The registry record documents a pilot study intended to investigate exercise-related blood-pressure response in people with hypertension and the role of spinal cord stimulation during exercise. For the primary endpoint, it reports a mean change of 8.67 for the spinal cord stimulation arm and 16.29 for the exercise intervention arm. The corresponding reported participant counts are 1 and 5, and a standard error of 1.82 is posted for the exercise intervention mean.
Those summaries do not answer the comparative question. The registry says that values are missing or not estimable for a two-arm comparison, and no analysis results are posted. No treatment contrast, confidence interval, or p-value is reported. The means cannot be interpreted as evidence that stimulation did or did not change the exercise pressor response relative to the listed exercise intervention.
The record also leaves key aspects of the design and analysis unclear. It labels the study randomized and crossover, but the arm description assigns participants unable to tolerate stimulation to the exercise intervention. It does not explain treatment sequence, crossover periods, the endpoint population, or the handling of missing data. Total enrollment is recorded as 9, while the posted outcome counts cover 1 and 5 participants; the record does not reconcile those figures.
Accordingly, the posted results are best understood as limited descriptive information from a completed pilot study, not as a definitive estimate of a comparative treatment effect. The absence of an estimable comparison does not establish that the interventions are equivalent or different. It means the registry record does not provide the analysis needed to assess that question.
13. Why This Trial Matters Statistically
This study raises statistical issues that are important when interpreting small clinical trials. Its registered crossover model calls for clarity about whether participants receive multiple conditions and how within-participant observations are analyzed. Yet the arm description makes the exercise intervention sound like an alternative for people who cannot tolerate stimulation. The registry does not reconcile those descriptions, so readers cannot identify the intended comparison structure from the record alone.
The distinction between descriptive and comparative results is also central. Means are posted for both arms, but the registry states that a two-arm comparison is not estimable. A comparison requires more than placing arm means side by side: it requires a defined estimand, suitable data, and an analysis that reflects the design. Without that, the descriptive values should not be treated as an estimate of the treatment effect.
The reported endpoint counts are small relative to the recorded enrollment, and the spinal cord stimulation result is based on 1 participant. This makes transparent reporting of the analysis population, missing data, and uncertainty especially important. The registry does not report those details or an inferential analysis. These gaps illustrate why registration information and posted results must be read together with attention to what is and is not documented.
The study’s stated focus is a specific physiological response during exercise in people with hypertension. Statistically, the record is informative about the question the investigators intended to study and about the limited endpoint summaries posted. It does not provide a reliable comparative estimate or enough information to determine how the crossover design was implemented.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The primary limitation is that the registry does not report an estimable comparison for the continuous endpoint. The posted results are arm-level means, with a standard error for only one arm. There is no reported confidence interval, p-value, or model-based estimate of the treatment contrast. The primary statistical question therefore remains unanswered by the posted analysis.
Endpoint counts are 1 for spinal cord stimulation and 5 for the exercise intervention, while recorded enrollment is 9. The registry does not explain the difference or identify the analysis population. It does not describe missing observations, withdrawals, exclusions, or whether all enrolled participants contributed to the outcome. These omissions prevent assessment of how representative the reported endpoint results are of the enrolled group.
The design description is also incomplete. Randomized allocation and a crossover model are listed, but the exercise-arm description ties assignment to inability to tolerate spinal cord stimulation. Treatment order, periods, washout, and crossover-specific analysis are not reported. The endpoint population is not specified, while the study summary refers to different population descriptions for its two aims. The record does not clarify which population contributed to the posted endpoint values.
Finally, the registry does not report the trial’s statistical analysis plan, sample-size justification, multiplicity approach, missing-data method, or sensitivity analyses. The safety counts are based on small recorded groups and are not accompanied by further adverse-event terms. These limitations concern what can be established from the registry record; they do not identify why information is absent or what analyses may have been conducted outside it.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Spinal Cord Stimulation to Treat Hypertension — NCT02828436.
- Registry record last updated 2020-09-16; status last verified 2020-08.
- Results first posted 2020-09-16.
- 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
The registry describes a completed randomized crossover pilot study, without masking, sponsored by the University of Minnesota. Its aims concern exercise blood-pressure response in people with hypertension and spinal cord stimulation during exercise. Total enrollment is recorded as 9.
The primary endpoint is change in the exercise pressor reflex from baseline, described as change in blood pressure during exercise and measured in mmHG. The posted mean is 8.67 for spinal cord stimulation, based on 1 participant, and 16.29 for the exercise intervention, based on 5 participants; the latter has a reported standard error of 1.82. The record states that a two-arm comparison is not estimable and posts no analyses.
Serious and other adverse event counts are recorded as 0 in both groups, with 0 deaths. The record does not explain the endpoint counts in relation to enrollment, reconcile the crossover designation with the arm descriptions, or report an analysis plan.