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 Gabapentin for Insomnia Symptoms and Nighttime Vasomotor Symptoms (VMS) in Peri- and Postmenopausal Women (NCT02040532), a na na study. The primary outcome is Tolerability of Gabapentin.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02040532 |
| Phase | NA |
| Condition | Menopause, Hot Flashes, Vasomotor Disturbance |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 32 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Massachusetts General Hospital |
| Results posted | Yes |
2. Clinical Question
Population
Peri- and postmenopausal women with vasomotor symptoms were the intended population. The registry lists menopause, hot flashes, and vasomotor disturbance as conditions. Enrollment was 32 participants; the primary analysis population consisted of all 26 participants who initiated gabapentin. The registry record does not explain the disposition of enrolled participants who did not initiate treatment.
Intervention
Participants received open-label gabapentin at bedtime, with dose titration described as 100mg for 1 week, 300mg for 3 weeks, and 600mg for 3 weeks. The stated aim was to assess tolerability and preliminary efficacy for insomnia symptoms and nighttime vasomotor symptoms.
Comparator
There was no comparison group. The study is listed as single-group, with no allocation and no masking. Consequently, the registry record does not describe a randomized or controlled treatment comparison.
Primary question
The primary endpoint asks whether participants could increase the dose from 300-mg to 600-mg and remain on the higher dose for the duration of the trial. Tolerability was assessed through self-report questionnaires and reports of adverse events at study contacts. The registry record does not report the numerical primary endpoint result, so the proportion meeting this definition cannot be read from the posted results.
The study’s stated broad goal was to collect pilot data about tolerability and preliminary efficacy. Its hypothesis anticipated that the majority of participants would be able to increase and tolerate treatment, with insomnia symptoms and nighttime vasomotor symptom frequency improving. That is the investigators’ stated hypothesis, not a reported finding. The absence of a comparator means changes observed during participation would not, by themselves, establish that gabapentin caused those changes.
3. Trial Design
This was a completed, single-group, open-label pilot study sponsored by Massachusetts General Hospital. The registry lists phase as NA, allocation as NA, and masking as none. It records enrollment of 32 and identifies one intervention, gabapentin. The study began in 2014-01 and had primary completion in 2015-08.
The treatment description specifies a bedtime dose schedule: 100mg for 1 week, followed by 300mg for 3 weeks, then 600mg for 3 weeks. This was a titration regimen rather than a comparison of assigned treatment arms. Because the study was open-label and had no control group, participants and study staff were not masked to treatment, and the posted record does not offer a like-for-like control comparison.
The primary endpoint population is described as all 26 participants who initiated gabapentin. This is distinct from the listed enrollment of 32. The registry record does not explain why the two counts differ, describe the disposition of participants who did not initiate treatment, or give a participant flow account beyond the primary analysis population statement.
The primary endpoint timeframe is listed as baseline, the Week 4 visit, and study completion at 7 weeks. The endpoint description says tolerability was assessed at week 1, week 4, and week 7 contacts using the SAFTEE-SI and CPFQ questionnaires and by prompting participants to report adverse events at each study visit. The registry lists eight outcome measures but no analysis entries. A detailed statistical analysis plan, sample-size justification, and any interim analysis plan are not reported in the registry record.
With this design, the study can describe the experience of the treated group and the recorded counts. It cannot isolate treatment effects from changes over time, expectations, or other influences because there is no concurrent comparator. The registry record’s stated scope is pilot data on tolerability and preliminary efficacy; the design should be read in that exploratory context.
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 | Open-label Gabapentin |
|---|---|
| STARTED | 32 |
| Received at Least One Dose of Medication | 26 |
| COMPLETED | 20 |
| NOT COMPLETED | 12 |
Reasons for not completing this period:
| Reason | Open-label Gabapentin |
|---|---|
| Lost to Follow-up | 1 |
| Physician Decision | 4 |
| Adverse Event | 4 |
| Withdrawal by Subject | 3 |
Analysis population for the primary outcome, as defined in the registry: All 26 participants who initiated treatment with gabapentin were included in this analysis.
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 | Open-label Gabapentin |
|---|---|---|
| Participants analysed | 26 | |
| Age, Continuous | years | 55.31 (SD 4.5) |
| Sex: Female, Male: Female | Participants | 26 |
| Sex: Female, Male: Male | Participants | 0 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 2 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 24 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 10 |
| Race (NIH/OMB): White | Participants | 16 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Region of Enrollment: United States | Participants | 26 |
| Highest Level of Education: Less than College Graduate | Participants | 18 |
| Highest Level of Education: College Graduate/Baccalaureate Degree | Participants | 4 |
| Highest Level of Education: Graduate Degree | Participants | 4 |
| Employment: Employed Full-Time | Participants | 8 |
| Employment: Employed Part-Time | Participants | 6 |
| Employment: Retired or Unemployed | Participants | 8 |
| Employment: Disabled, Unable to work, on Medical Leave | Participants | 4 |
| Marital Status: Never Married | Participants | 7 |
| Marital Status: Divorced or Separated | Participants | 5 |
| Marital Status: Widowed | Participants | 2 |
| Marital Status: Presently Married or Living with Partner | Participants | 12 |
| Gynecological History: Perimenopausal | Participants | 5 |
| Gynecological History: Naturally Postmenopausal | Participants | 18 |
| Gynecological History: Surgically Postmenopausal | Participants | 3 |
| Years since last menstrual period (LMP): <1 Years | Participants | 5 |
| Years since last menstrual period (LMP): 1-5 Years | Participants | 13 |
| Years since last menstrual period (LMP): >5 Years | Participants | 8 |
| Number of Children: No Children | Participants | 12 |
| Number of Children: 1 to 4 Children | Participants | 14 |
| Smoking History: Current Smoker | Participants | 4 |
| Smoking History: Non-Current Smoker | Participants | 22 |
| Baseline BMI | kg/m^2 | 29.4 (SD 6.6) |
| Provider Status: Has Doctor/Nurse Providing Regular Care | Participants | 25 |
| Provider Status: Does not have Doctor/Nurse Providing Regular Care | Participants | 1 |
6. Primary Endpoint
The registry lists the primary outcome as Tolerability of Gabapentin, measured over Baseline, Week 4 visit, and study completion at 7 weeks.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is tolerability of gabapentin, defined by whether a participant could increase the dose from 300-mg to 600-mg and remain on the higher dose for the duration of the trial. This definition focuses on reaching and continuing the planned higher dose; it is not itself a measure of insomnia improvement or reduction in nighttime vasomotor symptoms.
The record says tolerability was assessed by self-report at the week 1, week 4, and week 7 contacts. Participants completed the SAFTEE-SI and CPFQ questionnaires, and were prompted to report adverse events at each study visit. The timeframe is described as baseline, Week 4 visit, and study completion at 7 weeks. The registry does not report questionnaire scores, a count of participants who met the dose-based definition, or a percentage for this endpoint.
A dose-tolerance endpoint is useful in a pilot study because it describes whether participants could follow the planned titration and continue at the intended higher dose. It can inform the feasibility of delivering that regimen in a later study. In general, tolerability is distinct from efficacy: remaining on a dose does not show that symptoms changed, and symptom changes do not by themselves establish that a regimen was tolerable for all participants.
The record identifies insomnia symptoms and nighttime vasomotor symptoms as study aims, but the posted primary endpoint is tolerability. Without numerical outcome results for that endpoint, the registry record does not establish how many participants reached or maintained the 600mg dose.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes the design and the population used for the primary endpoint: a single-group, open-label study with 32 enrolled participants and 26 participants who initiated treatment included in the primary analysis. It also defines tolerability in terms of dose escalation from 300-mg to 600-mg and remaining on the higher dose. However, it does not report a numerical result for this endpoint. The stated hypothesis that the majority would tolerate the higher dose must therefore remain a hypothesis rather than a conclusion supported by a posted endpoint estimate.
The safety record lists 26 participants at risk for serious adverse events and 0 affected. For other adverse events, it lists 26 at risk and 11 affected. These are counts in the open-label gabapentin group, not comparative estimates. The record does not report the serious-event terms, and deaths are not reported in the registry record. These counts should not be treated as a complete description of all possible safety outcomes beyond what the record lists.
The study’s scope includes preliminary efficacy for insomnia symptoms and nighttime vasomotor symptoms, but the primary endpoint is tolerability. Numerical results for symptom outcomes are not reported in the registry record. Therefore, the posted information cannot establish the direction or magnitude of symptom change, nor how precisely any such change was estimated.
In general, an estimate describes the observed result in the participants studied, while its precision depends on the amount and variability of the data. A confidence interval, when reported, communicates a range of values compatible with the data under the chosen statistical method. No primary endpoint estimate or confidence interval is reported in the registry record, so the uncertainty around the endpoint cannot be quantified from the posted results.
The single-group design also limits causal interpretation. Without a comparator, changes over the study period cannot be separated from natural symptom variation, expectations associated with open-label treatment, or other concurrent influences. Those are general considerations for uncontrolled studies, not findings about what occurred in this trial. The record lists no analysis entries, so adjusted estimates, inferential tests, or model-based results are not available to interpret.
Overall, the posted results support a description of the study structure and the recorded safety counts, but not a numerical conclusion about the primary tolerability endpoint or symptom efficacy. The absence of a reported estimate is not evidence that the endpoint was either met or not met. It means the registry record does not provide the result needed to assess that question.
9. Statistical Methods Explained
The statistical interpretation begins with the design. This is a single-group study with open-label treatment, no allocation, and no masking. Those characteristics determine what comparisons are possible: the record describes outcomes among participants receiving gabapentin, but it does not provide a separate control group for estimating a between-group treatment contrast.
What does a single-group result describe?
In general, a single-group result is a description of the participants observed under the study conditions. It may summarize counts, proportions, or changes over time, depending on the endpoint and the analysis. Such a description does not automatically identify a treatment effect. Without a concurrent comparator, other explanations for an observed change cannot be ruled out by the treatment-group data alone. This is especially relevant when the study is open-label, because knowledge of treatment may influence expectations, reporting, or study interactions. These are general design considerations, not claims that any particular influence occurred in this study.
How should the primary endpoint be understood?
The endpoint is a participant-level tolerability definition: being able to increase the dose from 300-mg to 600-mg and remain on the higher dose for the duration of the trial. The record describes 26 participants who initiated treatment as the primary analysis population. For a binary endpoint, a complete report would ordinarily identify how many participants met the definition and how many were included in the denominator, and might also report a proportion with an uncertainty interval. The registry record does not report the primary endpoint count, proportion, or confidence interval. It is therefore not possible to assess the endpoint’s observed frequency or precision from the posted results.
What do counts and uncertainty mean?
For a count endpoint, the count states how many participants experienced the defined event. For a proportion, the numerator is interpreted relative to a stated denominator. A confidence interval is a statistical range that reflects sampling uncertainty under its assumptions; it does not guarantee that the true value lies within the interval. Wider intervals generally indicate less precision, while narrower intervals indicate greater precision. No interval for the primary endpoint is reported in the registry record, and no new estimate can be reconstructed in the registry record.
In general, small pilot studies tend to have limited precision for estimating event proportions, particularly when events are uncommon. This is a general statistical point and is not a calculated assessment of this study’s power or precision. The record’s enrollment and primary analysis population counts do not substitute for a reported endpoint result.
Why does the missing comparator matter?
A randomized comparison can support a direct contrast between assigned groups, subject to the design and analysis assumptions. This study has no randomized comparison: the registry lists a single group and no allocation. Any within-group change, if reported, would combine the effects of time, treatment exposure, measurement, and other influences that are not separated by a control arm. Accordingly, no treatment-versus-control effect estimate is available from the described design.
What can be inferred from the safety counts?
The serious adverse event record lists 0 affected among 26 at risk, and the other adverse event record lists 11 affected among 26 at risk. These are observed counts for the listed categories. They do not identify the severity, duration, or clinical course of the other events, and the record does not list serious-event terms. In general, a zero count in a study group does not prove that an event cannot occur; it describes what was recorded in the participants at risk during the study. No comparative safety estimate can be made without another group.
What is the role of sample-size planning?
The registry record does not report a sample-size justification for the trial. Any sample-size illustration based on an observed effect is a planning exercise, not an observed outcome and not evidence that a study had adequate power. In general, a planning calculation depends on assumptions about the target effect, significance level, allocation, and statistical model. If a calculation uses a fraction of an observed effect, it explores a hypothetical future design; it does not change the result observed in the pilot. The record does not provide the primary endpoint estimate needed to assess such an illustration against the tolerability outcome.
Power is the probability that a specified analysis will detect an effect of a defined size under stated assumptions. It is not a measure of the probability that a treatment works, and retrospective “observed power” is not a substitute for an estimate and confidence interval. The registry record does not report a power calculation for the study. Thus, no conclusion about planned or achieved power should be attached to the posted data.
Finally, the record lists eight outcome measures and no analysis entries. It does not report model specifications, adjustment methods, handling of repeated measurements, or a detailed inferential plan. These methods are not reported in the registry record, so it is not possible to evaluate assumptions or reproduce an analysis beyond the descriptive details that are posted.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists eight outcome measures and no analysis entries. The record does not describe which outcomes were treated as primary or secondary beyond identifying tolerability of gabapentin as the primary outcome, nor does it report a multiplicity adjustment or a hierarchy for testing multiple outcomes. A detailed statistical analysis plan is not reported in the registry record.
Multiplicity is a general concern when several outcomes or several statistical tests are examined. As the number of tests increases, the chance of at least one apparently unusual result can increase if each test is interpreted in isolation. Some studies address this through prespecified outcome hierarchies, adjusted significance thresholds, or other procedures. The registry record does not report whether any such approach was planned or used. Since no analysis entries are listed, there are no posted test results for which an adjustment can be evaluated.
The primary analysis population is explicitly described as all 26 participants who initiated gabapentin. The registry does not describe an intention-to-treat population, a per-protocol population, or other analysis sets. It also does not report how missing questionnaire data, missed study contacts, or incomplete treatment exposure were handled. These missing-data methods are not reported in the registry record.
In general, missing data can affect estimates when the participants with recorded outcomes differ from those without them. Statistical approaches depend on the outcome, the amount and pattern of missingness, and assumptions about why data are absent. No assumptions or sensitivity analyses addressing missing data are reported. The enrollment count of 32 and the primary analysis population of 26 should therefore be reported as distinct the registry entries, without assuming why they differ or how the difference was handled analytically.
Because the numerical primary result is absent, neither the impact of missing observations nor the consequences of multiple outcome testing can be assessed from the posted results. That uncertainty concerns reporting and analysis documentation; it does not establish that data were missing or that a particular adjustment was required.
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 |
|---|---|---|---|
| Open-label Gabapentin | 0 | 26 | 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 |
|---|---|
| Open-label Gabapentin | 11 of 26 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Open-label Gabapentin |
|---|---|---|
| Headaches | Nervous system disorders | 9 of 26 |
| Sweating | Respiratory, thoracic and mediastinal disorders | 8 of 26 |
| Feeling drowsy during the day | General disorders | 8 of 26 |
| Hot flashes | Pregnancy, puerperium and perinatal conditions | 7 of 26 |
| Nasal congestion | Respiratory, thoracic and mediastinal disorders | 6 of 26 |
| Feeling tired/fatigue | General disorders | 6 of 26 |
| Problems falling asleep | General disorders | 4 of 26 |
| Weight gain | Metabolism and nutrition disorders | 4 of 26 |
| Stomach/abdominal discomfort | Gastrointestinal disorders | 4 of 26 |
| Gas | Gastrointestinal disorders | 4 of 26 |
The registry lists 26 participants at risk for serious adverse events, with 0 affected. It lists 26 participants at risk for other adverse events, with 11 affected. These are counts for the open-label gabapentin group, not comparisons against an untreated or alternative-treatment group.
The count of 0 serious adverse events means none were recorded in that listed category among the participants at risk in this record. In general, a zero count does not establish that the underlying risk is zero; it describes the observed experience in the recorded group. The registry does not provide serious adverse event terms. Deaths are not reported in the registry record.
The other adverse event count indicates that 11 participants were recorded as affected in that category. The record does not identify the specific events, their severity, timing, duration, or whether they led to dose changes or discontinuation. It is therefore not possible to characterize the nature or clinical importance of those events from these counts alone.
These figures should be read within the study’s open-label, single-group design and the stated safety reporting. They do not establish comparative safety, and they are not the primary tolerability result. The primary endpoint’s numerical result is not reported in the registry record.
12. What the Result Does, and Does Not, Mean
The registry record describes a pilot study designed to assess tolerability and preliminary efficacy of bedtime gabapentin for insomnia symptoms and nighttime vasomotor symptoms in peri- and postmenopausal women with vasomotor symptoms. It specifies a dose titration schedule and defines the primary endpoint by participants’ ability to increase from 300-mg to 600-mg and remain at the higher dose for the trial duration.
What the posted results do show is the study structure, the primary analysis population, and safety counts. Enrollment was 32, and the primary analysis included all 26 participants who initiated treatment. The serious adverse event count was 0 among 26 at risk, and 11 participants were affected in the other adverse event category among 26 at risk. The record does not give details of the other events.
What the posted results do not show is the numerical result for the primary tolerability endpoint. There is no reported count or proportion of participants who met the dose-based definition, and no confidence interval is reported. The record also does not provide numerical results for insomnia symptoms or nighttime vasomotor symptom frequency. The investigators’ hypothesis about tolerability and symptom improvement is not a substitute for observed results.
In general, a pilot study can provide preliminary information about whether a regimen and outcome assessment are feasible, while estimates from a small study may remain uncertain. The registry record does not include a numerical estimate with which to judge the precision of the primary endpoint. Nor can a change over time in a single group, if available, distinguish treatment effects from other explanations without a comparator.
Accordingly, the record supports a description of the planned regimen, endpoint definition, participant counts, and posted safety counts. It does not support a conclusion about the proportion tolerating the higher dose, the size of any symptom change, or a causal treatment effect. Those questions remain unanswered by the numerical results reported in the registry.
13. Why This Trial Matters Statistically
This study illustrates why a clear endpoint definition and a reported endpoint result are both essential. The registry defines tolerability in a concrete way: participants must increase the dose from 300-mg to 600-mg and remain on the higher dose for the trial duration. That definition identifies what the primary question means, but without the observed count or proportion, readers cannot determine how frequently it was met.
The distinction between enrollment and the primary analysis population also matters. The record lists enrollment of 32 and states that all 26 participants who initiated treatment were included in the primary analysis. Reporting those counts separately helps readers understand which participants the endpoint population describes. The reason for the difference and the disposition of the other enrolled participants are not reported in the registry record.
The open-label, single-group design is another important statistical feature. It can describe experience during the treatment regimen, but it cannot provide a controlled estimate of what would have happened under a different condition. This matters when interpreting preliminary efficacy aims: without a comparator, any symptom changes cannot be attributed to gabapentin on the basis of this design alone.
Finally, the safety counts are useful only within their definitions and reporting limits. The record lists no serious adverse events among those at risk, and lists 11 participants affected by other adverse events. The specific other events and their clinical detail are not reported. These counts add descriptive context but do not replace the primary tolerability outcome.
Statistically, the main lesson is that study aims, endpoint definitions, analysis populations, and numerical results answer different questions. The registry provides substantial design detail but lacks the primary endpoint estimate needed to judge the stated tolerability question. That gap limits interpretation without implying what the unreported result would have been.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The most direct limitation for interpreting the primary question is that the registry record does not report a numerical result for tolerability. Although it defines the endpoint and identifies the analysis population, it gives no count or proportion of participants who increased to 600mg and remained on that dose. Precision therefore cannot be assessed from a reported estimate or confidence interval.
The study is open-label and single-group, with no allocation and no comparator. This prevents a like-for-like comparison and limits causal interpretation of any changes over time. The registry’s stated aim includes preliminary efficacy for insomnia symptoms and nighttime vasomotor symptoms, but numerical results for those outcomes are not reported in the registry record.
There is a difference between the listed enrollment of 32 and the primary analysis population of 26 participants who initiated treatment. The reason for this difference, participant disposition, and any outcomes for those who did not initiate are not reported in the registry record. It also does not describe a broader analysis population or sensitivity analyses.
The safety information is limited to counts: 0 serious adverse events among 26 at risk and 11 participants affected by other adverse events among 26 at risk. Serious-event terms, the specific other events, their severity, timing, and consequences are not reported. Deaths are not reported in the registry record.
The record lists eight outcome measures and no analysis entries. Statistical methods beyond the endpoint description, including handling of missing data, multiplicity procedures, model specifications, and a sample-size justification, are not reported in the registry record. These omissions restrict assessment of analysis assumptions and completeness. They do not establish that a particular outcome occurred or that a particular analysis was or was not conducted outside what the registry records.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Gabapentin for Insomnia Symptoms and Nighttime Vasomotor Symptoms (VMS) in Peri- and Postmenopausal Women — NCT02040532.
- Registry record last updated 2019-08-07; status last verified 2019-07.
- Results first posted 2017-02-27.
- 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
NCT02040532 is a completed, open-label, single-group pilot study sponsored by Massachusetts General Hospital. It enrolled 32 peri- and postmenopausal women with vasomotor symptoms and evaluated bedtime gabapentin using a titration schedule of 100mg for 1 week, 300mg for 3 weeks, and 600mg for 3 weeks.
The primary endpoint was tolerability, defined as increasing the dose from 300-mg to 600-mg and remaining on the higher dose for the duration of the trial. The primary analysis population comprised all 26 participants who initiated treatment. The numerical result for this endpoint is not reported in the registry record.
The safety record lists 0 serious adverse events among 26 at risk and 11 participants affected by other adverse events among 26 at risk. Specific event details are not reported. With no comparator and no posted numerical primary result, the registry supports description of the design and counts, but not a controlled treatment-effect estimate.