Obstructive Sleep Apnea Treatment to Improve Cardiac Rehabilitation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Obstructive Sleep Apnea Treatment to Improve Cardiac Rehabilitation (NCT02005445), a randomized na study. The primary outcome is WHO Disability Assessment Scale 2 Scores.

2. Clinical Question

The study was intended to examine whether treating obstructive sleep apnea could influence the effectiveness of cardiac rehabilitation. Its broader stated interests included exercise capacity, disability, and quality of life. The registered primary outcome focused on disability-related functional status; the registry record does not report a comparative result for that measure.

Because only 1-2 participants completed the study in each arm, the record says that outcome data are not presented due to confidentiality concerns. It also says no analysis was performed because recruitment did not reach a level considered sufficient for meaningful analysis. Consequently, the clinical question remains unanswered by the posted primary outcome data. The record does not establish whether CPAP or HLSE led to better functional status, nor does it provide an estimate of the size or precision of any difference.

3. Trial Design

This was a randomized, single-masked, parallel-group clinical trial. The registry lists CPAP as a device intervention and Healthy Lifestyle and Sleep Education (HLSE) as a behavioral intervention. The descriptions identify CPAP as continuous positive airway pressure and HLSE as healthy living and sleep education. The record does not explain who was masked or how masking was maintained, so those details are not reported in the registry record.

The study addressed obstructive sleep apnea and coronary heart disease in U.S. Veterans receiving cardiac rehabilitation. Its stated purpose was to evaluate the impact of obstructive sleep apnea treatment on the effectiveness of rehabilitation, including exercise capacity, disability, and quality of life. The registered primary outcome was the WHO Disability Assessment Scale 2.0 score at 12 weeks. The registry lists enrollment as 4.

The study start date was 2014-10-01, and the primary completion date was 2017-12-29. Its status is terminated. The registry record attributes the inability to recruit a sufficient number of patients for meaningful analysis to closing of the cardiac rehabilitation program. It reports that only 1-2 participants completed the study in each arm and that outcome data were withheld because of confidentiality concerns.

Although randomization is listed, the record does not report the sequence-generation method, allocation concealment, or any stratification or blocking. It also does not give further details about treatment delivery, adherence, follow-up procedures, or the masking procedure. These omissions limit the extent to which the design can be reconstructed from the registry record. No completed comparative analysis is available to assess the intended contrast between the interventions.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: As we were unable to recruit a sufficient number of patients for meaningful analysis, due to closing of the cardiac Rehabilitation program, no analysis was performed. Because there were only 1-2 participants completing the study in each arm, data are not presented due too confidentiality concerns.

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 WHO Disability Assessment Scale 2 Scores, measured over 12 weeks.

The primary endpoint was the WHO Disability Assessment Scale 2.0 score at 12 weeks. The scale measures functional status, with a stated range of 0-48; higher scores indicate more disability. It is relevant to the study’s rehabilitation focus because disability and everyday functioning are outcomes that may reflect how a health condition affects a person’s activities.

A disability measure can complement measures focused on symptoms or physiological function. In a rehabilitation study, it may help characterize whether participants’ functional limitations change during the intervention period. The registry record describes the endpoint but does not provide scores, a treatment contrast, or a measure of uncertainty. It also does not report an analysis of this endpoint.

The record states that data are not presented because only 1-2 participants completed the study in each arm and confidentiality concerns applied. Therefore, the endpoint’s scale and interpretation can be described, but the posted record cannot show how scores differed between CPAP and HLSE, whether scores changed over time, or how precisely any treatment difference was estimated.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does randomization contribute?

In general, randomization assigns participants to study groups through a chance-based process. Its purpose is to reduce systematic differences between groups at the start of a trial, including differences that researchers may not have measured. When enough participants are enrolled and outcomes are observed, this can support a fair comparison of the assigned interventions. Randomization does not guarantee that groups will be alike in every feature, and it cannot compensate for a lack of outcome data.

The registry lists this study as randomized and parallel, with CPAP and HLSE as the intervention groups. The method used to generate assignments and the process for concealing allocation are not reported in the registry record. The record also does not provide an analysis that would show how assignment was reflected in the endpoint results.

What would an outcome comparison estimate?

In general, an unadjusted comparison estimates the difference between groups using the outcome summaries as recorded, without accounting for other measured characteristics. An adjusted comparison uses a statistical model to account for specified factors. Either approach requires outcome observations and a defined analysis. For the primary outcome in this trial, scores and a comparative estimate are not reported, and no analysis was performed. It is therefore not possible to describe an unadjusted or adjusted treatment effect.

The WHO Disability Assessment Scale 2.0 is scored from 0-48, with higher values indicating more disability. A group summary could describe observed functional status, while a difference between groups could describe the contrast at the registered assessment time. Those summaries would still need uncertainty measures to convey how much the estimate might vary because of limited data. None are available in the registry record for this endpoint.

How should uncertainty be understood?

In general, a confidence interval combines an estimate with an indication of its statistical uncertainty under a specified model. A narrow interval indicates greater precision than a wide interval, but precision is distinct from whether an effect is clinically important. A p-value, when reported, describes how compatible the observed data are with a statistical null model under the assumptions of the analysis. It does not measure the probability that a treatment works or the probability that the null hypothesis is true.

These concepts cannot be applied to a treatment contrast that was not estimated. The registry provides no primary-outcome confidence interval or p-value. Given the limited completion described in the record, even an available estimate would require cautious interpretation; but no numerical estimate should be reconstructed from information that is not reported.

What is over-dispersion, and does it matter?

In general, over-dispersion occurs when observed variation is greater than a statistical model expects. It can affect the uncertainty assigned to estimates, particularly for count outcomes. Analysts may use a model that allows greater variability when the outcome and data support it. The primary outcome is a disability scale score, and the registry record does not describe a fitted statistical model or report a dispersion estimate. There is no basis to assess over-dispersion or to claim that a particular correction was used.

What can adverse-event counts tell us?

In general, adverse-event counts describe events observed and recorded during follow-up. Serious events and other events are distinct categories in the registry summary. Counts alone do not establish that an intervention caused an event, and comparisons based on very few observations are imprecise. The record lists counts for each group, but does not provide event terms for serious events. The counts should therefore be read descriptively, not as a formal comparative safety analysis.

Can a planning calculation replace the missing analysis?

No. A sample-size calculation is a planning exercise that asks how much information might be needed to detect a specified effect under stated assumptions. It is not an observed treatment effect, and it cannot recover results that were not analyzed or reported. The registry record does not provide an observed primary-outcome effect on which to base a planning illustration. The trial’s own sample-size justification and design assumptions are not reported in the registry record.

More broadly, a statistical plan would usually specify the primary analysis, analysis population, handling of missing outcomes, and any adjustments or sensitivity analyses. Those details are not reported in the registry record. Because no primary analysis was performed and participant outcome values are unavailable, the registered design alone cannot establish what the intervention comparison would have shown.

10. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when a study makes several statistical comparisons or tests multiple outcomes. In general, the more questions tested, the greater the chance that at least one result may appear statistically notable by chance alone. A statistical plan can identify which outcome is primary and specify whether adjustments or a hierarchy of tests will be used. The registry record identifies the WHO Disability Assessment Scale 2.0 at 12 weeks as the primary outcome, but does not report a multiplicity strategy or a complete statistical analysis plan.

The study’s brief description mentions exercise capacity, disability, and quality of life as areas of interest. The registry lists 1 outcome measure. The record does not provide results for additional measures or clarify whether other outcomes were planned outside the registry listing. Any multiplicity procedures are not reported in the registry record.

Missing outcome information is central to interpretation. The record says no analysis was performed because recruitment was insufficient for meaningful analysis following closure of the cardiac rehabilitation program. It also says that only 1-2 participants completed the study in each arm and that outcome data are not presented because of confidentiality concerns. The record does not describe the number of missing observations at each assessment, reasons for individual missingness, or any method for addressing missing data.

Analysis populations are also not specified. The registry record does not state whether an intention-to-treat, per-protocol, or other population was planned for the primary analysis. In general, an intention-to-treat approach retains participants in their randomized groups, while other approaches may depend on treatment received or protocol adherence. Without an analysis and without details of the intended population, no such approach can be attributed to this trial. These reporting gaps mean that the intended handling of multiplicity, missing outcomes, and analysis populations cannot be evaluated.

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.

Most frequent non-serious adverse event terms

The registry safety summary reports zero serious adverse events among 2 participants at risk in the CPAP group and zero among 2 at risk in the HLSE group. Deaths are recorded as zero in each group. For other adverse events, the record reports zero among 2 at risk in CPAP and one among 2 at risk in HLSE. No serious adverse event terms are listed.

These are small descriptive counts. They do not establish that the groups have the same safety profile, nor do they show that an intervention caused or prevented an event. With so few participants represented, the absence of a recorded serious event cannot rule out events that might occur in a larger or different population. Likewise, the other adverse-event count in HLSE does not by itself establish a treatment-related risk.

The record does not provide further detail about the nature, timing, severity, or relatedness of the other event. The counts should be interpreted as the adverse-event information posted in the registry, rather than as a complete or precise estimate of comparative safety.

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

The record documents a randomized comparison of CPAP and healthy lifestyle and sleep education in a cardiac rehabilitation setting, with functional status as the registered primary outcome. Its primary measure was the WHO Disability Assessment Scale 2.0 at 12 weeks. The registry also documents why an outcome analysis was unavailable: the cardiac rehabilitation program closed, recruitment was insufficient for meaningful analysis, and only 1-2 participants completed the study in each arm. Outcome data were not presented due to confidentiality concerns.

What this means is that the posted record cannot answer whether the groups differed on the primary outcome. There are no reported scale scores, changes, effect estimates, confidence intervals, or p-values. It cannot show the direction or magnitude of a treatment contrast, and it cannot establish the precision of any contrast. No conclusion that the interventions were equivalent, that one was superior, or that either changed disability is supported by the posted primary outcome information.

That absence of a result is not the same as a finding of no effect. A study can be unable to estimate an effect because of limited recruitment or missing outcome information even if a difference exists. Conversely, the stated purpose and randomized design do not establish that a difference exists. Distinguishing those possibilities requires outcome data and an analysis, neither of which is reported for the primary endpoint.

The safety counts offer only a narrow descriptive account. The record lists no serious adverse events or deaths in either arm and one other adverse event in HLSE. These counts are too limited to establish a comparative safety pattern, and they do not answer the primary disability question.

The study’s stated aims included exercise capacity and quality of life as well as disability. The available registry information does not support conclusions on those broader areas. Overall, the record describes an intended clinical comparison that ended without a reportable primary outcome analysis. Its importance for interpretation lies in recognizing the difference between an inconclusive record and evidence for or against a treatment effect.

13. Why This Trial Matters Statistically

This trial illustrates that randomization is valuable only when the study also obtains enough usable outcome information to support a comparison. Random assignment can help address confounding in a completed analysis, but it cannot create precision when recruitment is limited, nor can it replace outcomes that were not analyzed or presented. The registry lists enrollment as 4 and reports only 1-2 completions in each arm. The primary outcome data are unavailable, leaving the intended contrast unestimated.

It also shows why operational events matter to statistical interpretation. The registry attributes the insufficient recruitment to closing of the cardiac rehabilitation program. This is not a statistical finding about CPAP or HLSE, but it affected the study’s ability to answer its research question. Recruitment and retention determine how much information is available for estimation and how credible a comparison can be.

The record is also a useful reminder that a registered endpoint is not itself a result. Naming the WHO Disability Assessment Scale 2.0 and its score range clarifies what the study intended to measure, but without reported participant scores there is no treatment estimate to interpret. Statistical concepts such as confidence intervals, p-values, or adjustment for multiplicity only become relevant to a result when an analysis has been carried out and reported.

Finally, a terminated study with no primary analysis should not be mistaken for a negative trial. The absence of an estimate leaves uncertainty unresolved. Transparent reporting of recruitment barriers, the lack of analysis, and the confidentiality reason for withholding data helps readers distinguish an unavailable result from evidence that a treatment has no effect.

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 is that the primary outcome was not analyzed or presented. The registry record states that recruitment was insufficient for meaningful analysis following closure of the cardiac rehabilitation program. It reports only 1-2 participants completing the study in each arm and says the outcome data are not presented because of confidentiality concerns. Without those data, no comparative estimate or measure of precision can be assessed.

The record contains limited information about methods beyond randomized, single-masked, parallel design. It does not report how the random sequence was generated, how allocation was concealed, who was masked, or whether masking was successful. It does not describe adherence, treatment exposure, follow-up procedures, or baseline characteristics. These omissions prevent fuller evaluation of the trial’s conduct and comparability of the groups.

The statistical plan is also not reported. The registry does not specify the planned analysis model, the analysis population, how missing observations would be handled, or whether there were any multiplicity adjustments. No protocol or sample-size justification is described in the registry record. Given the absent outcome analysis, these details cannot be checked against the analysis that was actually performed.

The safety information is sparse. The posted record gives event counts but no serious-event terms, and it provides no further details about the other adverse event. The small number of participants represented limits the usefulness of these counts for comparing safety. These limitations are specific to the available record and do not establish what unreported outcomes or procedures might have shown.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Obstructive Sleep Apnea Treatment to Improve Cardiac Rehabilitation — NCT02005445.
• Registry record last updated 2019-07-05; status last verified 2019-06.
• Results first posted 2019-07-05.
• 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

NCT02005445 is a randomized, single-masked, parallel-group study of CPAP versus Healthy Lifestyle and Sleep Education in U.S. Veterans with obstructive sleep apnea and coronary heart disease receiving cardiac rehabilitation. The registry lists enrollment as 4 and the study status as terminated. The study start date was 2014-10-01, and the primary completion date was 2017-12-29.

The primary outcome was WHO Disability Assessment Scale 2.0 functional status at 12 weeks, with higher scores on its 0-48 range indicating more disability. The registry says no analysis was performed because recruitment was insufficient after the cardiac rehabilitation program closed. It reports 1-2 participants completing in each arm and says outcome data are not presented due to confidentiality concerns.

The safety summary records no serious adverse events or deaths in either group and one other adverse event in HLSE. No comparative primary-outcome result is available.