Feasibility of Improving Sleep Apnea Treatment Adherence After Brain Injury: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Feasibility of Improving Sleep Apnea Treatment Adherence After Brain Injury (NCT04221009), a na na study. The primary outcome is Narrative Evaluation of Intervention Interview (Post-intervention Qualitative Interview).

2. Clinical Question

3. Trial Design

This was a completed, single-group behavioral feasibility study. The registry lists an enrollment of 17, no allocation to treatment groups, and no masking. The intervention was a four-session manualized program derived from MI and CBT and adapted with cognitive accommodations. The stated goal was to test the feasibility and acceptability of delivering this approach to Veterans with TBI and OSA. The registry describes no like-for-like control comparison.

The study began on 2020-08-03 and had a primary completion date of 2022-03-31. The registry status is COMPLETED. The phase is listed as NA, which is consistent with a behavioral feasibility study rather than a drug-phase description. The sponsor is the VA Office of Research and Development.

The primary endpoint was a Narrative Evaluation of Intervention Interview (NEII), a 16-item semi-structured interview conducted after the intervention, up to 8 weeks after completion. The registry says the interview data were qualitative and analyzed thematically. All 13 participants who completed the study also completed the NEII. Secondary outcomes named in the record were the Epworth Sleepiness Scale, Fatigue Severity Scale, and Functional Outcomes of Sleep Questionnaire.

The registry lists four outcome measures, but does not report a numerical intervention effect or the results of the qualitative thematic analysis. It also reports no analyses. Details such as the full protocol, specific eligibility criteria, intervention delivery fidelity procedures, and any analysis plan are not reported in the registry record.

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: All 17 participants who agreed to participate were enrolled in the study and assigned to the single arm of the study.

Overall Study

Reasons for not completing this period:

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Narrative Evaluation of Intervention Interview (Post-intervention Qualitative Interview), measured over Post-intervention (up to 8 weeks after completion of the single arm intervention).

The primary endpoint was participant feedback obtained with the Narrative Evaluation of Intervention Interview (NEII) after the intervention. The NEII is described as a 16-item semi-structured interview designed to elicit feedback about an intervention. Interviews occurred post-intervention, up to 8 weeks after completion of the single-group program. The registry states that all 13 participants who completed the study also completed the interview.

The endpoint is qualitative: the data were to be examined using thematic analysis, and the registry labels the outcome as a number of themes. This type of endpoint can organize participants’ accounts into recurring topics, concerns, or experiences. In a feasibility study, those accounts can help describe whether the intervention was acceptable and identify aspects of delivery that may warrant attention in later research. That is a general role of qualitative feedback, not a report of what participants said in this study.

The registry record does not report the themes, their definitions, their frequency, or illustrative interview findings. It therefore does not support a conclusion about how acceptable participants found the intervention or which parts they considered useful or difficult. The interview endpoint also does not itself provide a controlled estimate of change in PAP adherence. No such comparative estimate is reported.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods depend on the question being asked and on the type of outcome collected. Here, the study is described as a single-group feasibility study, and the primary endpoint is qualitative interview feedback. The registry record does not report a statistical analysis plan or analyses. The following explains the relevant concepts in general and distinguishes them from methods actually documented for this study.

What does a single-group design estimate?

A single-group study observes participants receiving an intervention without a separate comparison group. It can describe whether the intervention was delivered, whether participants completed study procedures, and what participants report about their experience. If repeated measures are collected, a single group can also describe observed changes over time. But without a concurrent comparison group, a change cannot be attributed uniquely to the intervention. Other influences, such as natural variation, changes in care, or repeated measurement, may contribute. These are general limits of causal interpretation; the registry does not report a comparative analysis for this study.

The study’s stated focus was feasibility and acceptability. Those aims differ from testing whether an intervention outperforms another approach. A feasibility study may inform the design of later research by documenting whether procedures can be carried out and by identifying issues for consideration. The registry does not report a formal progression criterion or a prespecified threshold for deciding whether feasibility was achieved.

How should qualitative thematic analysis be understood?

Qualitative thematic analysis works with interview material rather than reducing responses to a single treatment-effect estimate. Analysts identify and organize patterns in participants’ accounts, then interpret those patterns in relation to the study question. The number of themes is not, by itself, a measure of the size of an intervention effect. Themes also require context: the meaning of a theme depends on how it was defined, what interview material supported it, and how the analysis was conducted.

The registry describes the NEII as a 16-item semi-structured interview and states that the data were analyzed thematically. It does not report the resulting themes, the analysis procedures in detail, whether multiple analysts were involved, or how interpretation was checked. Accordingly, readers cannot assess the thematic findings or the way the analysis was carried out from the registry record alone. That absence does not show that thematic analysis was not performed; it means the findings and further methods are not reported in the registry record.

What can outcome scales contribute?

The registry lists the Epworth Sleepiness Scale, Fatigue Severity Scale, and Functional Outcomes of Sleep Questionnaire as secondary outcomes. In general, a scale can convert responses into a score that researchers summarize or compare over time. Interpreting a score requires knowing how it was scored, which participants contributed data, when it was measured, and how missing responses were handled. The registry does not report these details or the secondary-outcome results. No score change or treatment effect should be inferred from the outcome names alone.

A confidence interval is a general way to express uncertainty around an estimate. Its width depends on factors including the amount of information in the data and the variability of the outcome. A p-value, in general, describes how compatible data are with a specified statistical model and null hypothesis; it is not a measure of the probability that a treatment works. Neither a confidence interval nor a p-value for an intervention effect is reported for this study. For the qualitative primary endpoint, a numerical treatment-effect interval would not substitute for the missing thematic findings.

Why do comparison and distribution assumptions matter?

A planning calculation for a two-arm study ordinarily depends on assumptions about the target effect, variability, significance level, power, allocation, and analysis method. The registry describes planning illustrations using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a fraction of an observed effect. These are assumptions for planning illustrations, not a description of this trial’s single-group design or an analysis of its results. No numerical planning outputs are reported in the registry record in the information available for this account.

In general, over-dispersion means that observed variability is greater than a statistical model assumes. When that happens, methods that rely on the smaller variance assumption may understate uncertainty. This is a general consideration for count outcomes, not a reported finding in this study. The primary endpoint is described as qualitative thematic analysis, and no count-model analysis is reported. The registry’s label of a number of themes does not establish that themes were treated as independent count observations.

Planning sample sizes are not observed power. A planning illustration asks how much information might be needed under stated assumptions; it does not show that a completed study had a particular probability of finding an effect. Since this study had no randomized comparison and the registry reports no analysis, its planning illustrations cannot be used to claim observed power or evidence of comparative efficacy.

10. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when a study evaluates several outcomes or performs several statistical tests. In general, testing many hypotheses can increase the chance of obtaining at least one apparently unusual result by chance. Researchers may address this through a prespecified hierarchy, adjustment methods, or by treating analyses as exploratory. The registry lists one qualitative primary endpoint and three named secondary outcomes, but does not report a multiplicity strategy, a hierarchy of secondary analyses, or inferential results. No adjustment method should be assumed.

The record identifies 17 enrolled participants and says that all 13 participants who completed the study also completed the NEII. It does not describe the outcomes or interview data for participants who did not complete the study, nor does it state how missing scale measurements were handled. The number included in each secondary-outcome analysis is not reported in the registry record.

Analysis populations, such as an intention-to-treat population or a per-protocol population, are not reported in the registry record. These labels describe which participants are included in an analysis; the choice can affect what the result represents. Without a reported definition and participant-level accounting, the analysis population for any outcome cannot be determined.

Missing data can matter when the chance that an outcome is observed is related to a participant’s experience or outcome. General approaches include describing missingness, using assumptions about the missing values, and checking whether conclusions are sensitive to those assumptions. The registry record does not report a missing-data approach or sensitivity analysis. The fact that study completers completed the interview does not establish that interview results are available for all enrolled participants.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry lists the single intervention group with 17 participants at risk for serious adverse events and zero serious adverse events. It also lists 17 participants at risk for other adverse events and zero other adverse events. Deaths are listed as zero. These are the recorded counts for the study, not estimates of risk beyond the observed group.

A zero count means that no events in the relevant category were recorded among the participants at risk in this study. It does not prove that the event is impossible, or that the same count would be observed in a larger or different group. With a small study, uncommon events may not be observed even when they remain possible. That is a general limitation of interpreting zero-event counts, not a new estimate for this trial.

The registry record does not list serious-event terms and does not provide detail about the methods or timing of adverse-event collection. The count of zero other adverse events should likewise be read as the posted count, rather than as evidence that no symptoms or other experiences occurred outside the registry’s adverse-event categories. These safety counts do not establish a comparative safety profile because there was no separate control group.

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

The study addresses an important research question: whether a manualized behavioral intervention informed by MI and CBT, and adapted with cognitive accommodations, can be delivered and is acceptable to Veterans with TBI and OSA. The registry describes a four-session intervention and a qualitative interview intended to gather participant feedback. That focus is appropriate to a feasibility question, which is different from a definitive test of comparative treatment effects.

The record establishes that 17 participants were enrolled and that all 13 participants who completed the study also completed the NEII. It also lists zero serious adverse events, zero other adverse events, and zero deaths in the intervention group. These are descriptive details about enrollment, interview completion among study completers, and recorded events.

The record does not report the NEII themes or results for the secondary outcomes. It therefore does not establish how participants evaluated the intervention, whether PAP adherence changed, or whether sleepiness, fatigue, or functional outcomes changed. The intervention’s stated purpose should not be mistaken for a demonstrated result. Likewise, the absence of a control group means there is no direct comparison with usual care or another intervention.

In general, feasibility findings can inform whether and how a larger study might be designed. They do not automatically show that an intervention is effective, nor do they establish that the same delivery approach will be feasible in other populations or settings. The registry record does not report a sample-size justification, a complete protocol, or a statistical analysis plan, so those aspects cannot be assessed from the posted information.

The appropriate interpretation is bounded: the registry documents a completed single-group feasibility study with a post-intervention qualitative endpoint, a reported count of study completers who completed that interview, and the listed adverse-event counts. It does not provide the primary thematic findings or comparative efficacy evidence. No clinical recommendation follows from these registry entries alone.

13. Why This Trial Matters Statistically

Feasibility studies occupy a distinct role in clinical research. They examine whether an intervention and its study procedures can be carried out, and can collect information relevant to later research. The study’s focus on adapting an MI- and CBT-informed program with cognitive accommodations addresses a practical design question for work with Veterans who have TBI and OSA. The registry states that the intervention was manualized and delivered over four sessions.

Statistically, it is important not to confuse evidence about deliverability or participant experience with evidence of treatment effect. The single-group design has no concurrent control arm, while the primary endpoint is qualitative interview feedback. Those features fit a feasibility aim, but they do not produce a controlled estimate of how the intervention compares with another approach. The qualitative endpoint also requires its themes and supporting analysis to be reported before readers can assess the findings.

The distinction between planned and observed evidence matters as well. The registry describes hypothetical planning illustrations based on a two-arm framework, while the actual study is single-group. A planning calculation is not a result from the trial and is not observed power. Keeping those concepts separate prevents a hypothetical design assumption from being read as evidence that an intervention effect was detected.

Finally, clear reporting of participant flow, outcome availability, analysis populations, missing-data handling, and qualitative methods helps readers judge what a feasibility study has established and what should be examined next. Several of these details are not reported in the registry record. That limits statistical interpretation, but does not negate the study’s stated purpose: to examine the feasibility and acceptability of an adapted intervention.

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 for interpretation is the absence of reported endpoint findings. Although the NEII is described and its thematic-analysis approach is named, the registry record does not give the themes or qualitative results. Consequently, acceptability and participant experience cannot be assessed from the registry entries.

The single-group design has no control arm and no allocation to different treatments. It therefore cannot provide a like-for-like comparison or isolate intervention effects from other influences. This matters particularly for any interpretation of change in PAP adherence or secondary outcomes, for which results are not reported.

The record lists an enrollment of 17 and says all 13 study completers also completed the interview, but does not explain the status or outcome data for participants who did not complete the study. It does not report how missing secondary-outcome data were handled, which participants were included in each analysis, or whether any sensitivity analyses were conducted. The registry reports no analyses.

Further methodological details are not reported in the registry record, including the full statistical plan, a sample-size justification, detailed qualitative-analysis procedures, and the results for the named secondary outcomes. The registry does not report a multiplicity approach. These omissions limit reproducibility and assessment of uncertainty.

The adverse-event record reports zero events in the listed categories, but does not provide serious-event terms or detailed collection procedures. As with any small feasibility study, the observed event counts cannot establish the frequency of uncommon harms in a broader population. These limitations should be considered alongside the study’s stated feasibility purpose, rather than treating the record as a definitive comparative evaluation.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Feasibility of Improving Sleep Apnea Treatment Adherence After Brain Injury — NCT04221009.
• Registry record last updated 2024-07-08; status last verified 2024-03.
• Results first posted 2024-07-08.
• 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.

18. Record Summary

NCT04221009, titled “Feasibility of Improving Sleep Apnea Treatment Adherence After Brain Injury,” is a completed, single-group behavioral feasibility study sponsored by the VA Office of Research and Development. Enrollment was 17. The intervention was a manualized, four-session program derived from MI and CBT and adapted with cognitive accommodations.

The primary endpoint was a post-intervention NEII, described as a 16-item semi-structured qualitative interview analyzed thematically. All 13 participants who completed the study also completed the interview. The registry record does not report the resulting themes or numerical results for the named secondary outcomes: the Epworth Sleepiness Scale, Fatigue Severity Scale, and Functional Outcomes of Sleep Questionnaire.

The adverse-event record lists zero serious adverse events, zero other adverse events, and zero deaths. No analyses are reported. With no control group and no reported outcome findings, the registry supports a description of the study’s design and recorded counts, but not a comparative estimate of intervention effect.