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 The Effects of Obstructive Sleep Apnea and Its Intervention on Coronary Heart Disease (NCT02059993), a randomized na study. The primary outcome is Change of Daytime Systolic Blood Pressure (SBP) and Diastolic Blood Pressure (DBP) Pre-treatment and Post-treatment.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02059993 |
| Phase | NA |
| Condition | Hypertension, Metabolic Disorder |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 83 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Chinese Pulmonary Vascular Disease Research Group |
| Results posted | Yes |
2. Clinical Question
The trial asked whether long-term CPAP treatment was associated with changes in daytime systolic and diastolic blood pressure among people with obstructive sleep apnea (OSA) and coronary heart disease (CHD). Its registry description also identifies hypertension and metabolic disorder as conditions of interest. The primary outcome was the change in blood pressure from baseline to follow-up at 36 months.
Population
Participants with CHD and OSA were described in the study summary. The registry lists hypertension and metabolic disorder as conditions. Further eligibility details, such as age criteria and how OSA or CHD was defined, are not reported in the registry record.
Intervention
The intervention was continuous positive airway pressure. The CPAP group received fixed-level treatment titrated using an automated pressure. Mean use was at least 4 hours per night, according to the arm description.
Comparator
The control group received standardised anti-hypertension medications according to the current guideline, as described in the registry. Whether other aspects of care were identical between groups is not reported in the registry record.
Primary question
How did daytime systolic and diastolic blood pressure change from baseline to follow-up at 36 months in the randomized groups? Numerical group results and a direct between-group estimate are not reported in the registry record.
3. Trial Design
This was a randomized, single-masked, parallel-group study with an enrollment of 83. It was marked completed. The recorded start was 2009-01 and primary completion was 2013-12. The listed phase was NA, which is not a drug-development phase designation for this device intervention.
Participants were assigned to a CPAP group or a control group. The CPAP description specifies fixed-level titration using an automated pressure and mean CPAP use of at least 4 hours per night. The control description says participants received standardised anti-hypertension medications according to the current guideline. The particular method used to generate or conceal the random allocation is not reported in the registry record.
The trial is described as single-masked, but the identity of the masked group—participants, clinicians, outcome assessors, or another party—is not reported in the registry record. The study model was parallel, meaning the listed arms represent separate groups rather than a crossover sequence. The registry does not report whether participants could change treatment groups or how treatment adherence was assessed beyond the CPAP use description.
The primary outcome concerned change in daytime systolic and diastolic blood pressure, measured in mm Hg at baseline and follow-up at 36 months. A change in Epworth Sleepiness Scale was listed as a secondary outcome. The registry lists three outcome measures and two analyses, but further detail about the analyses is not reported in the registry record. The study summary describes a hypothesis about blood pressure and metabolic disorder; numerical results for the stated primary outcome 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: A total of 243 patients were screened between January 2009 and June 2012. Out of 97 (39.9%) patients diagnosed with obstructive sleep apnea (OSA), 5 subjects declined to participate in the study, and 9 subjects were excluded because of the following: apnea-hypopnea index (AHI) \<15 (n = 8 patients) and severe heart failure (n = 1 patient).
Overall Study
| Stage | Continuous Positive Airway Pressure(CPAP) Group | Control |
|---|---|---|
| STARTED | 42 | 41 |
| COMPLETED | 40 | 37 |
| NOT COMPLETED | 2 | 4 |
Analysis population for the primary outcome, as defined in the registry: 4 participants withdrew before the end of study. Two subjects were lost to follow-up in the control group, and 4 patients (all of them had no SCCE) with very poor CPAP compliance were also excluded.
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
Population: A total of 243 patients were screened between January 2009 and June 2012. Out of 97 (39.9%) patients diagnosed with OSA, 5 subjects declined to participate in the study, and 9 subjects were excluded because of the following: AHI \<15 (n = 8 patients) and severe heart failure (n = 1 patient).
| Characteristic | Unit | Continuous Positive Airway Pressure(CPAP) Group | Control | Total |
|---|---|---|---|---|
| Participants analysed | 42 | 41 | 83 | |
| Age, Continuous | years | 62.0 (SD 6.8) | 62.7 (SD 6.7) | 62.4 (SD 6.6) |
| Sex: Female, Male: Female | Participants | 12 | 10 | 22 |
| Sex: Female, Male: Male | Participants | 30 | 31 | 61 |
| Region of Enrollment: China | participants | 42 | 41 | 83 |
| morning systolic and diastolic BP (mmHg): systolic BP | mm Hg | 146 (SD 8) | 148 (SD 11) | 147 (SD 9) |
| morning systolic and diastolic BP (mmHg): diastolic BP | mm Hg | 83 (SD 7) | 83 (SD 8) | 83 (SD 7) |
6. Primary Endpoint
The registry lists the primary outcome as Change of Daytime Systolic Blood Pressure (SBP) and Diastolic Blood Pressure (DBP) Pre-treatment and Post-treatment, measured over baseline and follow-up at 36 months.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | mm Hg |
| Endpoint classification | Continuous Endpoint |
The primary endpoint was change in daytime systolic blood pressure (SBP) and diastolic blood pressure (DBP) between pre-treatment baseline and follow-up at 36 months. Both are continuous measurements of blood pressure, and the registry specifies mm Hg as the unit. The outcome was described using means and standard deviations.
SBP and DBP capture different components of a blood-pressure reading. Assessing change over time can describe whether the measured values at follow-up differ from those at baseline. In a randomized comparison, the central treatment question is generally whether the amount of change differs between groups, rather than whether one group changed on its own. That is a general statistical distinction; the registry does not report the numerical group changes or the direct between-group estimate for this trial.
A mean describes the average measurement in a group, while a standard deviation describes the spread of individual measurements around that mean. Reporting both can convey the group average and the variability among participants, but neither alone indicates how precisely a treatment contrast has been estimated. Confidence intervals or other uncertainty estimates for this endpoint are not reported in the registry record.
Blood pressure was selected as the primary measure in the context of the study’s stated interest in OSA, CPAP, and hypertension. The registry summary also mentions metabolic disorder, but the primary endpoint described in the record is blood pressure. The particular measurement procedures, the exact visit windows, and any prespecified definition of the change score are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies the primary outcome and its timing, but does not report numerical SBP or DBP results. It therefore does not support a conclusion about the size, direction, or precision of the blood-pressure difference between the randomized groups. Numerical means, standard deviations, group changes, a between-group contrast, and uncertainty estimates for the primary outcome are not reported in the registry record. A p-value for that comparison is also not reported in the registry record.
The primary outcome is framed as change from baseline to follow-up at 36 months. A within-group change answers whether measurements differed over time among the participants included in that group’s analysis. It does not, by itself, establish that changes differed between groups. The randomized comparison is the relevant contrast for assessing how outcomes differed according to assignment, subject to the trial’s analysis and missing-data handling. Those details and the numerical contrast are not reported in the registry record.
The participant counts in the adverse-event record are not substitutes for primary-outcome results. Safety counts and blood-pressure measurements concern different outcomes, and the former cannot establish the magnitude or precision of the latter. Similarly, the study summary’s statement of a hypothesis is not an outcome result.
The registry describes exclusions and losses before completion: four participants withdrew before the end of the study; two control subjects were lost to follow-up; and four patients with very poor CPAP compliance were excluded. The record says these four had no SCCE, but does not define that abbreviation. It does not provide a complete participant flow or explain how these categories relate to each other. Consequently, the number enrolled should not be treated as the number contributing to each reported outcome.
The record says planning illustrations use an observed effect and specified assumptions, but the effect estimate and resulting planning counts are not reported in the registry record. Such planning values are not observed power and do not replace the trial’s outcome estimates. Overall, interpretation of the primary comparison is limited by the absence of its numerical results and uncertainty measures in the registry record.
9. Statistical Methods Explained
The registry identifies random allocation, single masking, and a parallel-group model. These features describe broad elements of trial design, not the full statistical analysis. The sequence-generation method, allocation concealment, identity of the masked party, and prespecified analysis plan are not reported in the registry record. It is therefore not possible to determine from the record exactly how the groups were formed or how the primary comparison was calculated.
What does a change score represent?
In general, a change score is a participant’s follow-up measurement compared with that participant’s baseline measurement. Group summaries can then describe average change and variation in change. Another general approach is to compare follow-up measurements between groups while accounting for baseline measurements. These approaches can yield different estimates, especially when baseline values vary, so knowing the chosen model matters. The exact calculation and model used for SBP and DBP are not reported in the registry record.
For a randomized trial, a treatment contrast should compare the groups rather than rely only on separate within-group tests. A difference between one group’s baseline and follow-up values does not by itself show that the group changed more or less than the other group. The registry does not report the primary between-group estimate, its standard error, confidence interval, or p-value. It also does not say whether SBP and DBP were analyzed together or as separate outcomes.
How should means and standard deviations be read?
As a general statistical explanation, the mean is an average and the standard deviation describes the spread of observations around that average. The standard deviation is not the same as the standard error: the former describes participant-level variability, while the latter describes uncertainty in an estimated mean. A confidence interval, when reported, gives a range of values compatible with the data and a stated method under its assumptions. No confidence interval for the primary outcome is reported in the registry record, so the precision of the estimated blood-pressure effect cannot be assessed from the numerical results.
Continuous outcomes are often analyzed with methods that rely on assumptions about the distribution of measurements or model residuals. The suitability of a method depends on the data and the analysis plan. The registry does not report distribution checks, transformations, covariate adjustments, or the model used. General explanations of these methods should not be mistaken for a description of what this trial actually did.
What do the planning assumptions mean?
The record describes planning illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. The illustrations consider an effect to detect expressed as a stated fraction of the observed effect. These are planning assumptions, not evidence about the trial’s actual analysis or a justification for its enrollment. The corresponding effect estimate and planning counts are not reported in the registry record.
In general, a planning calculation estimates how many participants may be needed under stated assumptions to detect a specified effect with a chosen probability, if the assumptions hold. That is distinct from observed power calculated after a trial; sample-size illustrations should not be interpreted as observed power. The registry does not report its original sample-size justification, target enrollment, or whether the actual enrollment was determined using the described illustration.
The use of a normal approximation is an assumption in the described planning calculation. A normal approximation can be useful for planning under suitable conditions, but the registry does not report diagnostics or explain whether the approximation was checked against the actual outcome data. None of these general methodological points supplies the missing primary-outcome estimates. The record’s reported design and planning description can be interpreted, but the effect and its precision remain unavailable in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists three outcome measures and two analyses. It identifies change in Epworth Sleepiness Scale as a secondary outcome and describes change in SBP and DBP as the primary outcome. The full list of outcome measures, the analyses corresponding to them, and which outcomes were included in each analysis are not reported in the registry record.
Multiplicity is the general statistical issue that can arise when several outcomes, time points, groups, or analyses are tested. If many hypotheses are examined, the chance of at least one apparently unusual result can increase unless the analysis plan accounts for that. Whether and how multiplicity was handled in this trial is not reported in the registry record. No adjustment method, testing hierarchy, or prespecified primary contrast is described beyond the stated SBP and DBP outcome.
The registry’s primary outcome description includes two blood-pressure measures and baseline and follow-up time points. The record does not say whether each measure was tested separately, whether a combined criterion was used, or how any multiple comparisons were interpreted. It also does not report interim analyses or stopping rules. Their presence or absence cannot be inferred from the record.
Missing-data information is limited. The record says four participants withdrew before study end, two control subjects were lost to follow-up, and four patients with very poor CPAP compliance were excluded; it notes that the latter four had no SCCE. It does not explain whether these groups overlap, how missing blood-pressure values were handled, or which participants were included in each analysis. The analysis population, imputation methods, and sensitivity analyses are not reported in the registry record. These omissions limit assessment of how attrition and exclusions may have affected the estimated comparison.
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 |
|---|---|---|---|
| Continuous Positive Airway Pressure(CPAP) Group | 1 | 42 | 2.4% |
| Control | 5 | 41 | 12.2% |
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 |
|---|---|
| Continuous Positive Airway Pressure(CPAP) Group | 0 of 42 |
| Control | 0 of 41 |
Most frequent serious adverse event terms
| Event term | Organ system | Continuous Positive Airway Pressure(CPAP) Group | Control |
|---|---|---|---|
| stroke | Nervous system disorders | 0 of 42 | 3 of 41 |
| acute myocardial infarction | Cardiac disorders | 0 of 42 | 2 of 41 |
| heart failure | Cardiac disorders | 1 of 42 | 0 of 41 |
Serious events with the highest arm-level rate: stroke (7.3%), acute myocardial infarction (4.9%), heart failure (2.4%).
The registry reports serious adverse events for 42 participants at risk in the CPAP group and 41 at risk in the control group. It records one affected participant in the CPAP group and five in the control group. These are counts of participants with serious adverse events, not estimates of the primary blood-pressure outcome. They do not by themselves describe event timing, duration, recurrence, or the uncertainty around a comparison.
The record lists zero affected participants in the “other” adverse-event category among 42 at risk in the CPAP group and among 41 at risk in the control group. The category definitions and the method used to collect these events are not reported in the registry record. Death counts are not reported in the registry record.
The listed serious-event terms are stroke at 7.3%, acute myocardial infarction at 4.9%, and heart failure at 2.4%. The record does not clarify the denominator or group attribution for these term-specific percentages, so they should be read as listed rather than used to infer participant counts or group-specific rates. The registry does not report further detail about severity grading, relatedness to treatment, or event-by-event timing.
12. What the Result Does, and Does Not, Mean
The registry record establishes that a randomized, parallel-group study compared CPAP with a control regimen described as standardised anti-hypertension medication, and that the primary outcome concerned change in daytime SBP and DBP through follow-up at 36 months. It also records exclusions and losses and provides limited serious and other adverse-event counts. Those details describe the study and the available registry entries; they do not supply the numerical primary-outcome comparison.
Without the group results and a between-group estimate, the size and direction of any difference in blood-pressure change cannot be determined from the registry record. Without an uncertainty interval or other precision measure, it is also not possible to judge how precisely that difference was estimated. The absence of a reported estimate is not evidence that there was no difference. Nor does the study’s hypothesis, design, or safety count establish the result of the primary endpoint.
More generally, statistical evidence about an average group contrast is not identical to a statement about every participant. A mean can conceal variation across individuals, and an estimate should be considered together with its uncertainty and the analysis population. These are general principles; participant-level blood-pressure results and a complete account of the analysis population are not reported in the registry record.
The serious-event counts should be interpreted separately from the efficacy endpoint. They do not establish a causal explanation for the events or a definitive safety comparison, particularly because event definitions, term denominators, and uncertainty estimates are not reported. The registry entry is therefore informative about the trial’s question, design, and selected recorded events, while important information needed to interpret its primary statistical result is not reported in the registry record.
13. Why This Trial Matters Statistically
This trial is statistically notable for asking a long-term question about blood pressure in people described as having both OSA and CHD, with follow-up at 36 months. The registry also describes random allocation and a parallel-group comparison. These design features frame a comparison over time, but design alone cannot establish the size or precision of an outcome difference.
The outcome is continuous and described using means and standard deviations. That makes it important to distinguish the average change within each group from the contrast between groups. It also makes reporting uncertainty important: averages alone do not show how precisely a difference has been estimated. Because the primary numerical results and their uncertainty are not reported in the registry record, this central statistical interpretation remains unresolved.
The record also illustrates why analysis populations and missing data matter. It reports withdrawal, loss to follow-up, and exclusion for very poor CPAP compliance, but does not explain their overlap or how the missing and excluded observations were treated. Excluding participants after randomization can affect what the resulting comparison represents; the actual impact cannot be assessed without fuller participant-flow and analysis details.
Finally, the planning assumptions described in the record should be kept distinct from trial findings. Planning calculations based on an observed effect are illustrations under stated assumptions, not observed power and not a substitute for reporting outcome estimates. The statistical importance of the trial lies in its clearly stated long-term comparison and endpoint, alongside the need for transparent outcome estimates, precision, and analysis-population reporting to interpret that comparison.
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 principal limitation for statistical interpretation is that numerical results for the primary SBP and DBP outcome are not reported in the registry record. Group means, standard deviations, changes, between-group estimates, and uncertainty measures are therefore unavailable. Without them, the magnitude, direction, and precision of the primary comparison cannot be assessed.
The record’s account of participant disposition is incomplete for evaluating the analysis population. It states that four participants withdrew before study end, two control subjects were lost to follow-up, and four patients with very poor CPAP compliance were excluded. It does not state whether these categories overlap or how many participants contributed to each outcome analysis. The meaning of SCCE is not reported in the registry record.
Further design and analysis details are not reported in the registry record, including eligibility criteria, OSA and CHD definitions, randomization procedures, the identity of the masked party, measurement procedures, the analysis model, handling of missing measurements, and any sensitivity analyses. The registry does not report whether multiplicity was addressed or whether interim analyses were planned or conducted. These points should be treated as unavailable rather than inferred.
The CPAP arm description records mean use of at least 4 hours per night, but the record does not provide adherence distributions or explain how compliance exclusions were determined. The serious-event term percentages lack a clearly stated denominator and group attribution. These limitations affect interpretation of both outcome reporting and safety summaries; they do not establish what the unreported results would have been.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: The Effects of Obstructive Sleep Apnea and Its Intervention on Coronary Heart Disease — NCT02059993.
- Registry record last updated 2020-07-16; status last verified 2020-07.
- Results first posted 2015-04-09.
- 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
NCT02059993, titled “The Effects of Obstructive Sleep Apnea and Its Intervention on Coronary Heart Disease,” is recorded as a completed, randomized, single-masked, parallel-group study with an enrollment of 83. Its recorded start was 2009-01 and primary completion was 2013-12. The intervention was CPAP; the control group received standardised anti-hypertension medications according to the registry description.
The primary outcome was change in daytime SBP and DBP from baseline to follow-up at 36 months, measured in mm Hg and described using means and standard deviations. Change in Epworth Sleepiness Scale was listed as a secondary outcome. Numerical results for the primary blood-pressure comparison are not reported in the registry record.
The record reports serious adverse events among participants at risk and lists stroke, acute myocardial infarction, and heart failure as serious-event terms. It also records withdrawals, loss to follow-up, and exclusions for very poor CPAP compliance, without a complete account of how these affected the analysis population. The statistical analysis plan and detailed missing-data methods are not reported in the registry record.