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 Cognitive Behavioral Treatments for Post-traumatic Stress Disorder (PTSD) Sleep Disturbance (NCT00108628), a randomized na study. The primary outcome is Weekly Number of Nightmares.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00108628 |
| Phase | NA |
| Condition | Post-traumatic Stress Disorder |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 134 |
| Arms in the primary outcome | n/a |
| Lead sponsor | US Department of Veterans Affairs |
| Results posted | Yes |
2. Clinical Question
Population
Veterans with Post-traumatic Stress Disorder and subjective sleep disturbance. The registry record describes the study purpose in these terms, but does not report more detailed eligibility criteria or participant characteristics.
Intervention
Imagery Rehearsal Therapy, a behavioral group psychotherapy intervention. The registry record does not give further details about session content, duration, or delivery.
Comparator
Sleep and Nightmare Management, also identified as a behavioral intervention. Additional information about its content and delivery is not reported in the registry record.
Primary question
The trial was intended to compare the interventions in relation to subjective sleep disturbance, with weekly number of nightmares named as the primary outcome. The outcome was scheduled for assessment at baseline and 1, 3, and 6 months post-treatment. The registry record does not report the observed values or an estimate of the difference between the groups, so the comparative result cannot be assessed from this record.
3. Trial Design
The registry identifies NCT00108628 as a randomized, single-masked, parallel-group trial. Its listed enrollment is 134, and its status is completed. The listed start is 2004-04 and primary completion is 2008-09. The sponsor is the US Department of Veterans Affairs. The phase is listed as NA.
The two arms were Imagery Rehearsal Therapy and Sleep and Nightmare Management. The study summary describes the purpose as comparing two cognitive behavioral group psychotherapy interventions for controlling subjective sleep disturbance in veterans with Post-traumatic Stress Disorder. Both interventions are categorized as behavioral. Further information about the treatment procedures, treatment duration, or how participants were assigned is not reported in the registry record.
Single masking means that the record identifies masking of one party, but it does not say who was masked. The registry also does not report the randomization method, whether allocation was concealed, or how masking was maintained. These omissions prevent a detailed appraisal of those design features, but they do not change the basic description of the study as a randomized parallel comparison.
The primary outcome was assessed at baseline and at 1, 3, and 6 months post-treatment. The record lists additional outcomes relating to sleep quality, nightmare effects, PTSD symptoms, depression, physical and mental health, and clinician-assessed PTSD. It does not report the sequence or timing of those secondary assessments beyond the primary outcome timeframe.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Before assignment: Ten participants dropped out prior to randomization.
Overall Study
| Stage | Imagery Rehearsal Therapy | Sleep and Nightmare Management |
|---|---|---|
| STARTED | 61 | 63 |
| Received One or More Sessions | 53 | 58 |
| Completed Treatment | 42 | 57 |
| COMPLETED | 41 | 53 |
| NOT COMPLETED | 20 | 10 |
Reasons for not completing this period:
| Reason | Imagery Rehearsal Therapy | Sleep and Nightmare Management |
|---|---|---|
| Withdrawal by Subject | 17 | 9 |
| Lack of Efficacy | 2 | 1 |
| Death | 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.
| Characteristic | Unit | Imagery Rehearsal Therapy | Sleep and Nightmare Management | Total |
|---|---|---|---|---|
| Participants analysed | 61 | 63 | 124 | |
| Age, Continuous | years | 59.79 (SD 3.18) | 59.06 (SD 3.86) | 59.42 (SD 3.55) |
| Sex: Female, Male: Female | Participants | 0 | 0 | 0 |
| Sex: Female, Male: Male | Participants | 61 | 63 | 124 |
| Region of Enrollment: United States | participants | 61 | 63 | 124 |
6. Primary Endpoint
The registry lists the primary outcome as Weekly Number of Nightmares, measured over Baseline and 1, 3, and 6 months post-treatment.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | weekly nightmares |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is weekly number of nightmares, expressed as a mean with standard deviation and measured in weekly nightmares. It is listed at baseline and 1, 3, and 6 months post-treatment. The record does not describe the instrument or procedure used to count nightmares, or how the measure was summarized when observations were missing.
As a general statistical point, an outcome expressed as a mean describes the average value in a group, while a standard deviation describes the spread of individual values around that average. The mean can help characterize the typical reported frequency, and the standard deviation gives context about variation among participants. Neither quantity, by itself, establishes whether groups differ or how precisely an estimated difference is known.
Weekly nightmare frequency is relevant to the stated study purpose because the trial concerned subjective sleep disturbance and included nightmare management interventions. Repeated assessments can describe how the outcome is recorded across follow-up, but a treatment comparison requires reported group results and a specified analysis. Those outcome values and the associated comparison are not reported in the registry record. The record also does not identify one follow-up time point as the sole primary comparison, so the scheduled assessments should not be treated as a single result.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies the trial question and primary outcome, but it does not provide the numerical primary-outcome results. No group means, standard deviations, estimated treatment difference, confidence interval, or statistical test result are reported in the available record. The treatment comparison therefore cannot be quantified or interpreted as favoring either intervention on the basis of this record.
The primary outcome was scheduled at baseline and 1, 3, and 6 months post-treatment. That is a set of repeated assessment times rather than one reported comparison. The registry record does not identify which follow-up assessment was intended to carry the main treatment contrast, whether change from baseline was analyzed, or how results across the assessment times were handled. It would be inappropriate to select a time point or infer a trend without reported values.
In general, a group mean describes the average outcome in that group, and a between-group estimate describes the contrast used to answer a comparative question. A confidence interval would communicate the range of values compatible with the data and analysis under its assumptions. A p-value, if reported, would address compatibility with a statistical null model; it would not by itself measure the size or practical importance of a difference. None of these inferential results for the primary outcome is reported in the registry record.
The record lists 134 enrolled participants, but does not report how many contributed primary-outcome data at each assessment or how participants were included in the analysis. Enrollment alone cannot establish the amount of information available for a particular comparison, especially when the outcome is assessed repeatedly. Missing-data handling and analysis-population definitions are not reported in the registry record.
The record lists 10 outcome measures and 0 analyses. The latter means that no analysis entries are present in the registry information; it does not establish what analyses may have been conducted outside the registry record. The absence of reported results is not evidence that the interventions had identical outcomes, nor does it establish that either intervention was better. The appropriate reading is that the comparative effect and its precision are not assessable from the posted results represented by this record.
9. Statistical Methods Explained
The registry describes a randomized, parallel-group design and a continuous primary outcome summarized as a mean and standard deviation. It does not report an outcome analysis or numerical treatment comparison. The general concepts below explain how such a design and outcome are commonly interpreted; they are not claims about procedures used in this trial unless explicitly identified in the registry record.
Randomization and parallel groups
In general, random assignment aims to make the groups comparable at the start of a trial with respect to measured and unmeasured characteristics. It supports a causal comparison when assignment is implemented as planned and participants are analyzed in a way that respects that assignment. The registry record says that allocation was randomized and that the model was parallel, meaning the trial had separate groups receiving the respective interventions rather than a crossover arrangement. The method used to generate the allocation sequence, conceal allocation, and analyze participants by assigned group is not reported in the registry record.
A parallel-group comparison generally contrasts outcomes between participants assigned to each arm. The record names Imagery Rehearsal Therapy and Sleep and Nightmare Management as the arms, but provides no analyzed group sizes or primary-outcome estimates. The total enrollment of 134 does not show how many participants had usable data at any follow-up or how the enrolled participants were distributed across the reported analyses.
Continuous outcomes and summary statistics
The primary endpoint is identified as weekly number of nightmares, with the parameter described as a mean and the dispersion described as a standard deviation. In general, a mean gives a measure of the group’s average outcome, whereas the standard deviation describes variability among individual observations. A standard deviation is not the same as the uncertainty in a group mean or in a between-group contrast. To assess the precision of a treatment comparison, an estimate and an uncertainty measure such as a confidence interval are needed. These are not reported for this outcome in the registry record.
The outcome is assessed at baseline and 1, 3, and 6 months post-treatment. Repeated measurements can be analyzed in different ways, including separate comparisons at selected assessment times or a model that uses measurements across time. Those approaches answer related but not identical questions and can make different assumptions. The registry record does not report which approach was used, whether baseline values were incorporated into the analysis, or how within-participant correlation across repeated measurements was handled. No particular model should therefore be attributed to the trial.
Masking and analysis details
The registry classifies the trial as single-masked. Masking can reduce the influence of expectations on aspects of trial conduct or assessment, depending on who is masked and how the outcome is collected. The identity of the masked party and the procedures used to maintain masking are not reported in the registry record. Because the primary outcome is a count of nightmares, the way participants reported or recorded it could matter to measurement, but the registry does not describe that process.
Methods such as confidence intervals, hypothesis tests, and regression models are general tools for quantifying a treatment contrast. Their interpretation depends on the estimand, analysis population, model assumptions, and handling of missing observations. The registry record does not report the statistical analysis plan, an inferential test, confidence intervals, or model specifications for the primary outcome. It also does not report interim analyses or a sample-size justification for the trial.
Planning illustrations and precision
The record includes assumptions for planning illustrations: a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation, with the effect to detect described as a stated fraction of the observed effect. Such an illustration is a hypothetical planning exercise, not a report of the trial’s observed statistical power. It cannot replace a confidence interval or an analysis of the trial data. The specific planning values are not reported in the registry record, and the record does not state that these assumptions were used to design the trial.
In general, the precision of an estimate depends on factors including the amount of outcome information available, variability, and the analysis method. The registry record gives no primary-outcome estimates or uncertainty measures from which to judge precision. No conclusion about the size, direction, or statistical compatibility of the intervention contrast can be drawn from the design description alone.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 10 outcome measures and names several secondary outcomes: the Pittsburgh Sleep Quality Index - Addendum, Nightmare Effects Survey, PTSD Military Checklist, Beck Depression Inventory, SF-36 Physical Component, SF-36 Mental Component, and Clinician-Administered PTSD Scale (CAPS). The primary outcome is weekly number of nightmares. The record does not give a complete analysis for these measures, or explain how their results were prioritized.
When a study examines multiple outcomes or assessment times, the number of statistical comparisons can affect how results are interpreted. In general, multiplicity procedures may be used to control the chance of misleading findings across a family of tests, but whether and how such procedures are appropriate depends on the planned questions. The registry record does not report a multiplicity adjustment, a hierarchy of outcomes, or a prespecified primary follow-up contrast. It also reports 0 analyses, so no outcome-specific statistical results are available in the record.
Missing-data methods are not reported in the registry record. The record does not state how many participants posted primary-outcome observations at baseline or at each post-treatment assessment, why any observations were absent, or whether imputation or another method was used. Analysis populations, including whether the primary analysis followed randomized assignment, are also not reported. These details matter because missingness and exclusions can affect both the size and interpretation of an estimated treatment difference. No assumptions about attrition, imputation, or analysis populations can be made from the enrollment count alone.
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 |
|---|---|---|---|
| Imagery Rehearsal Therapy | 0 | 53 | 0.0% |
| Sleep and Nightmare Management | 0 | 58 | 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 |
|---|---|
| Imagery Rehearsal Therapy | 0 of 0 |
| Sleep and Nightmare Management | 0 of 0 |
The safety fields list 53 participants at risk for serious adverse events in the Imagery Rehearsal Therapy arm and 58 in the Sleep and Nightmare Management arm. Serious adverse events affected 0 participants in each arm in the reported fields. These are the registry’s recorded counts; they should not be read as a complete account of all possible harms or as proof that no events occurred outside the recorded scope.
The fields for other adverse events list 0 participants at risk and 0 affected in both arms. With no participants listed as at risk in those fields, the entries do not provide a useful basis for comparing other adverse events between groups. Death counts are null, so deaths are not reported in the registry record. The record does not provide event descriptions, definitions, ascertainment procedures, or follow-up details that would support a broader safety assessment.
The enrollment count is not a substitute for the arm-specific at-risk counts. The record does not explain how the safety denominators were determined or whether they represent everyone enrolled or a subset. Without event-level information and fuller follow-up context, the safety fields should be interpreted narrowly as the counts recorded in the registry.
12. What the Result Does, and Does Not, Mean
The trial record establishes that a randomized, single-masked, parallel-group comparison was conducted between Imagery Rehearsal Therapy and Sleep and Nightmare Management. It identifies veterans with Post-traumatic Stress Disorder and subjective sleep disturbance as the population of interest, and weekly number of nightmares as the primary outcome. It also specifies assessments at baseline and 1, 3, and 6 months post-treatment.
What the record does not establish is the comparative result. It contains no reported primary-outcome values, treatment-effect estimate, confidence interval, or statistical test result. Therefore, the available registry information does not show whether the groups differed, in what direction any difference might have been, or how precisely a difference was estimated. This absence of a reported comparison should not be interpreted as evidence of no difference.
In general, a statistically estimated difference and its uncertainty are needed to distinguish the observed data from a qualitative description of the study question. Even a reported difference would need to be interpreted in light of the outcome scale, time point, analysis population, missing data, and design. The registry record does not provide those analytical details or outcome results for this trial.
The record’s safety entries report 0 participants affected by serious adverse events in each arm among the listed at-risk groups, while deaths are not reported. These entries are limited registry data and do not establish a comprehensive safety profile. The record’s summary should not be extended beyond the reported counts and the trial’s stated purpose.
Accordingly, the supported conclusion is descriptive: the study compared two behavioral group interventions and selected weekly nightmare frequency as its primary outcome, but the registry record does not report the results needed to quantify or interpret their relative outcomes.
13. Why This Trial Matters Statistically
This trial is statistically notable as a randomized comparison of two active behavioral interventions, rather than a comparison with no intervention. That design makes the intended question comparative: how the groups’ outcomes differed under the interventions being studied. The registry record identifies that question and its population, while leaving the numerical answer unreported.
The repeated primary-outcome schedule also illustrates why a clearly specified estimand matters. Weekly number of nightmares was assessed at baseline and 1, 3, and 6 months post-treatment. A reader needs to know which time point or longitudinal contrast is central, how baseline information is used, and how repeated observations are modeled before interpreting a treatment effect. Those analysis details are not reported in the registry record.
The record also demonstrates the distinction between trial registration and a complete statistical results report. Registration information can describe the design and planned outcomes, but an interpretable treatment comparison requires observed group data and an analysis with uncertainty. Although the record lists 10 outcome measures, it reports 0 analyses. As a result, neither the primary result nor the handling of secondary outcomes and multiple comparisons can be assessed.
For biostatisticians and clinical researchers, this example underscores that enrollment, randomization, and endpoint naming are not substitutes for effect estimates, precision measures, and transparent analysis details. Without those elements, the study question can be understood, but its statistical answer cannot be evaluated from the registry record.
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 interpretation is that the registry record does not report primary-outcome values or an analysis comparing the two groups. It also does not provide estimates or confidence intervals for the secondary outcomes. The listed outcome measures therefore cannot be used to determine the direction, magnitude, or precision of any treatment contrast.
The primary outcome is scheduled at multiple post-treatment assessments, but the record does not identify a single primary follow-up comparison or describe the handling of repeated measurements. The measurement instrument and the method used to ascertain weekly nightmare frequency are not reported. This limits assessment of how the endpoint was defined and collected.
Important design and analysis details are also absent: the randomization procedure, allocation concealment, identity of the masked party, statistical analysis plan, analysis populations, missing-data methods, and interim analyses are not reported in the registry record. The record does not report the trial’s sample-size justification. The planning assumptions listed in the record do not establish that those assumptions determined the trial’s design.
The enrollment figure does not supply arm-specific outcome denominators at each assessment. The serious adverse-event entries give at-risk counts and affected counts, but provide no event descriptions or fuller ascertainment context; deaths are not reported in the registry record. These limitations restrict interpretation of both the comparative outcome and the safety information. They do not establish that the trial lacked analyses or that any particular result occurred; they describe what cannot be evaluated from the registry record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Cognitive Behavioral Treatments for Post-traumatic Stress Disorder (PTSD) Sleep Disturbance — NCT00108628.
- Registry record last updated 2015-02-18; status last verified 2015-02.
- Results first posted 2015-02-18.
- 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
NCT00108628 is a completed randomized, single-masked, parallel-group trial sponsored by the US Department of Veterans Affairs. The listed enrollment is 134. The listed start is 2004-04 and primary completion is 2008-09. The trial compared Imagery Rehearsal Therapy with Sleep and Nightmare Management in veterans with Post-traumatic Stress Disorder and subjective sleep disturbance.
The primary outcome was weekly number of nightmares, recorded as a mean with standard deviation at baseline and 1, 3, and 6 months post-treatment. The registry lists 10 outcome measures and 0 analyses. It does not report the primary-outcome results, a treatment-effect estimate, or its precision. Serious adverse events affected 0 participants in each arm among those listed at risk; deaths are not reported in the registry record.