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 Obesity, Sleep Apnea, and Insulin Resistance (NCT02192684), a randomized na study. The primary outcome is Change in Apnea-hypopnea Index (AHI) Outcome Measure in Response to Pioglitazone or Placebo.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02192684 |
| Phase | NA |
| Condition | Insulin Sensitivity, Obstructive Sleep Apnea |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 45 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Stanford University |
| Results posted | Yes |
2. Clinical Question
Population
Patients with obstructive sleep apnea (OSA) are named for the primary AHI outcome. The registry’s brief summary describes randomization among participants considered at highest risk of diabetes, but the primary outcome’s population field is blank. The characteristics of participants included in the reported comparison are not reported in the registry record.
Intervention
Pioglitazone, described in the arm information as 45 mg orally once daily.
Comparator
Placebo, described as one pill daily.
Primary question
What happens to AHI over 8 weeks in the pioglitazone and placebo groups? The registry frames the endpoint as a change in AHI, but does not clarify whether the posted medians represent change scores or values at a particular assessment.
AHI is a measure of apnea and hypopnea events per hour. Comparing it between randomized groups is intended to assess whether the groups’ sleep-apnea measurements differ during the specified treatment period. The outcome is described as a measure of response to pioglitazone or placebo, but the posted information does not include a between-group effect estimate, confidence interval, or test of statistical significance. The median summaries alone therefore describe the groups, rather than establishing the size or precision of a treatment contrast.
The brief summary describes several related investigations: insulin resistance among overweight patients with OSA, a pioglitazone-versus-placebo intervention, a separate CPAP intervention, and screening-questionnaire assessments in community participants without known sleep apnea. The reported primary outcome specifically concerns AHI in the pioglitazone and placebo arms. Details linking the wider activities to the participants in this particular outcome are not reported in the registry record.
3. Trial Design
The registry lists a randomized, single-masked, parallel-group study. The primary outcome compares a pioglitazone arm with a placebo arm. The registry reports 45 participants enrolled overall; the outcome summaries list 30 participants in the pioglitazone arm and 15 in the placebo arm. Enrollment is not necessarily the same as the number contributing data to a particular outcome, and the registry does not explain whether any participants were excluded from the outcome summaries.
The record identifies the study phase as not applicable and classifies the study as “other.” Stanford University is listed as the sponsor. The recorded start is 2010-09, the primary completion is 2014-07, and the study status is completed. These dates describe the registry timeline; they do not establish when each participant received treatment or when individual outcome data were collected.
The brief summary describes randomization of participants at highest diabetes risk to pioglitazone or placebo, and separately describes a 12-week CPAP intervention. The primary AHI outcome, however, specifies an 8-week timeframe and concerns pioglitazone versus placebo. The relationship between the separate CPAP activity and the primary outcome is not reported in the registry record. Nor are the randomization procedure, allocation concealment, masking procedures, or the identity of the masked party reported.
The registry does not report a protocol-based sample-size justification, a detailed statistical analysis plan, or how the study’s broader activities were organized into analysis populations. The observed arm sizes should therefore be read as reported counts, not as evidence about the planned statistical power or the adequacy of the design.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Overall Study
| Stage | Pioglitazone | Placebo |
|---|---|---|
| STARTED | 30 | 15 |
| COMPLETED | 30 | 15 |
| NOT COMPLETED | 0 | 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 | Pioglitazone | Placebo | Total |
|---|---|---|---|---|
| Participants analysed | 30 | 15 | 45 | |
| Age, Continuous | years | 51 (SD 11) | 50 (SD 12) | 50.5 (SD 11.5) |
| Sex: Female, Male: Female | Participants | 10 | 5 | 15 |
| Sex: Female, Male: Male | Participants | 20 | 10 | 30 |
| Changes in sleep measure | Apnea-hypopnea index (AHI) events/hour | 36.9 (SD 11.9) | 40.8 (SD 12.3) | 38.9 (SD 12.1) |
| Insulin Sensitivity | mmol/L | 11.9 (SD 2.1) | 12.3 (SD 2.0) | 12.1 (SD 2.1) |
6. Primary Endpoint
The registry lists the primary outcome as Change in Apnea-hypopnea Index (AHI) Outcome Measure in Response to Pioglitazone or Placebo, measured over 8 weeks.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | AHI events/hour |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is titled “Change in Apnea-hypopnea Index (AHI) Outcome Measure in Response to Pioglitazone or Placebo.” AHI is expressed in events per hour and describes the frequency of apnea and hypopnea events during sleep. It is used as a quantitative measure of sleep-disordered breathing, allowing the registry to summarize the outcome numerically in each treatment group.
The registry specifies an 8-week timeframe and says the outcome is summarized by the median with interquartile range. The posted pioglitazone summary is a median of 35.8 events/hour, with an interquartile range of 21.0 to 49.0. The placebo summary is a median of 34.4 events/hour, with an interquartile range of 18.0 to 47.0. The corresponding outcome counts are 30 and 15.
Although the endpoint title calls the measure a change, the registry does not explain whether the posted numbers are changes from baseline, values at the 8-week assessment, or another summary. Baseline AHI values and the calculation of change are not reported in the registry record. This limits how the medians can be interpreted: they describe the posted outcome summaries, but do not by themselves establish the amount of change within either group or the difference in change between groups.
AHI is a relevant quantitative endpoint for the stated sleep-apnea question, but a group median does not show the full distribution or the experience of each participant. The interquartile range conveys the middle spread of values; it is not a confidence interval for the median or a measure of uncertainty in the treatment contrast.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted results give median AHI summaries for the two randomized groups at the outcome’s stated 8-week timeframe. The pioglitazone group has a reported median of 35.8 events/hour, with an interquartile range of 21.0 to 49.0; the placebo group has a reported median of 34.4 events/hour, with an interquartile range of 18.0 to 47.0. The record lists 30 participants for pioglitazone and 15 for placebo. These are descriptive summaries, not an estimate of the uncertainty around a between-group treatment effect.
The registry record does not report an analysis of the treatment contrast. There is no posted confidence interval, p-value, adjusted estimate, or test statistic for this endpoint. The registry also does not clarify whether the listed medians represent change from baseline or AHI values at an assessment. Consequently, the summaries cannot establish whether the groups differed statistically, how precise a possible difference might be, or the amount of change attributable to either treatment.
The interquartile ranges describe the middle half of the observed values in each group. Their overlap does not constitute a formal test of a group difference, and their width does not quantify uncertainty in the treatment effect. A proper comparison would require an analysis suited to the outcome and study design, with a clear definition of the endpoint and information about participants included in the analysis. Those details are not reported in the registry record.
The sample-size counts also matter for interpretation. There are 30 participants in the pioglitazone outcome group and 15 in the placebo outcome group, but the record does not explain why those counts differ or whether all enrolled participants contributed data. The overall enrollment count is 45. No account of missing outcome observations or exclusions is reported, so the relationship between enrollment and the analyzed participants cannot be assessed from the record.
The registry labels the study randomized and single-masked, features that can help limit bias when implemented as intended. But details about how randomization and masking were conducted are not reported. The posted arm summaries should therefore be read as the reported descriptive results, without assuming that unreported procedures or analyses were carried out.
The results support a narrow conclusion: the registry reports these median AHI summaries for the pioglitazone and placebo groups. They do not, on their own, show that one treatment changed AHI more than the other or establish the precision of any such contrast. No medical conclusion should be drawn from these descriptive figures alone.
9. Statistical Methods Explained
Randomized parallel-group comparison. The record describes randomized allocation and a parallel model, with separate pioglitazone and placebo groups. In general, randomization is used to reduce systematic differences between groups at the point of allocation. Parallel-group designs follow different participants in each assigned group rather than comparing each participant under both conditions. These design labels do not reveal how the allocation sequence was generated, how assignment was concealed, or how masking was implemented; those details are not reported in the registry record.
Median and interquartile range. The primary outcome is reported as a median with an interquartile range. In general, the median is the middle point of an ordered set of observations. The interquartile range gives the lower and upper bounds of the central half of the distribution. These summaries can be useful when observations are skewed or when a few extreme values could pull a mean away from the center. They describe location and spread among observed values, but do not show the complete distribution or provide an estimate of uncertainty in a comparison between groups.
For this outcome, the pioglitazone median is 35.8 events/hour, and its reported interquartile range is 21.0 to 49.0. The placebo median is 34.4 events/hour, and its reported interquartile range is 18.0 to 47.0. The registry does not state whether these are baseline-adjusted results, change scores, or values measured at the end of the 8-week period. Although the endpoint title refers to change, that wording alone does not resolve how the reported summaries were calculated.
Estimating a treatment contrast. A treatment comparison is usually expressed as an effect estimate, such as a difference in group summaries, together with a measure of uncertainty. A confidence interval is a general statistical tool that gives a range of values compatible with the data and the analysis assumptions. Its width helps readers judge precision; it is not a guarantee that the true value lies within a particular interval. No confidence interval or other inferential estimate for the AHI comparison is reported in the registry record.
A p-value, when reported, describes how unusual data at least as incompatible with a specified null hypothesis would be under the test assumptions. It does not measure the size or clinical importance of an effect. No p-value or test result for the primary AHI comparison is reported. The record lists zero posted analyses, so there is no reported inferential analysis to interpret alongside the descriptive medians.
Distribution and model choice. Statistical methods should match the outcome’s distribution and the question being asked. For skewed data, methods based on ranks or robust summaries may be considered; for outcomes analyzed using a model, assumptions should be checked. Over-dispersion is a general concern for count models when variability exceeds what a chosen model expects, and can make standard errors too small if ignored. AHI is expressed as events per hour, but the registry does not report the model, distributional assumptions, diagnostic checks, or any use of a count model. It would therefore be inappropriate to infer that a particular method was used or that over-dispersion was assessed.
Adjusted and unadjusted analyses. An unadjusted comparison uses the observed group data without accounting for other variables. An adjusted analysis incorporates specified covariates, potentially improving precision or addressing imbalance, depending on the design and assumptions. Neither an adjusted nor an unadjusted inferential result is reported for the primary endpoint. Covariates, adjustment methods, and any sensitivity analyses are not reported in the registry record.
Sample-size planning. A sample-size calculation is a planning exercise based on assumptions about the effect to detect, variability, significance level, power, and allocation. A planning illustration is not an observed result and does not show the power achieved by the completed study. The record does not report the trial’s own sample-size justification. Any displayed planning illustration based on an observed effect should be understood as a separate hypothetical calculation, not as the study’s original design calculation or an analysis of observed power. The registry’s stated illustration assumptions include a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the effect expressed as a fraction of the observed effect. The listed outcome groups are not equally sized, so those illustration assumptions should not be confused with the reported group counts.
What the reported summaries support. The medians and interquartile ranges describe central tendency and spread in each group. They do not supply a formal test, a measure of precision for a treatment contrast, or a basis for concluding that a difference is statistically meaningful. The missing definition of the reported AHI values, together with the absence of an inferential analysis, limits interpretation to the descriptive information that the registry reports.
10. Multiplicity, Missing Data and Analysis Populations
The record lists one primary outcome measure and zero posted analyses. It also reports zero posted secondary outcomes. This describes what is posted in the registry record; it does not establish that no other outcomes were collected or examined. The brief summary describes several related research activities, but the record does not explain their relationship to the registered outcome or identify a full set of planned analyses.
Multiplicity arises when multiple outcomes, comparisons, time points, or analytical choices are tested. In general, repeated testing can increase the chance of a positive finding arising by chance unless the analysis plan addresses that issue. A multiplicity adjustment or prespecified testing strategy is not reported in the registry record. Because no inferential results are posted for the primary comparison, there is no reported significance result to assess for multiplicity.
Missing-data handling is also not reported. The record does not state how many participants had an AHI measurement available, whether any outcome observations were missing, why data might be absent, or how missing observations were treated. The arm counts associated with the outcome are 30 for pioglitazone and 15 for placebo, while overall enrollment is 45; the record does not explain the relationship between these counts or whether the outcome counts reflect all enrolled participants.
The analysis population is not defined. The registry does not say whether results were analyzed according to randomized assignment, treatment received, or another rule, and it does not describe exclusions after randomization. The primary outcome’s population field is blank. Interim analyses, stopping rules, and a detailed statistical analysis plan are not reported in the registry record. These omissions limit the ability to evaluate whether the posted summaries reflect the originally planned analysis.
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 |
|---|---|---|---|
| Pioglitazone | 0 | 30 | 0.0% |
| Placebo | 0 | 15 | 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 |
|---|---|
| Pioglitazone | 2 of 30 |
| Placebo | 0 of 15 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Pioglitazone | Placebo |
|---|---|---|---|
| weight gain | Product Issues | 2 of 30 | 0 of 15 |
The registry reports zero serious adverse events among 30 participants at risk in the pioglitazone group and zero among 15 participants at risk in the placebo group. These are the reported serious-event counts for the two groups. The record does not provide serious adverse-event terms, and the list of top serious-event terms is empty.
For other adverse events, the registry lists 2 affected in the pioglitazone group, among 30 at risk, and 0 affected in the placebo group, among 15 at risk. These are counts, not a formal comparison of risk. No calculation of relative or absolute risk is needed to read the counts, and the record does not report an inferential safety analysis.
Death counts are not reported in the registry record. The absence of a posted death count should not be interpreted as confirmation that no deaths occurred. Likewise, zero recorded serious events in these groups does not establish that serious events are impossible or that the treatments have equivalent safety. The safety information is limited to the counts posted and does not give event descriptions, timing, severity details, or information about causality.
12. What the Result Does, and Does Not, Mean
The registry reports an 8-week primary AHI outcome framed as a change in response to pioglitazone or placebo. Its posted summaries are medians of 35.8 events/hour for pioglitazone and 34.4 events/hour for placebo, with interquartile ranges of 21.0 to 49.0 and 18.0 to 47.0, respectively. The outcome counts are 30 and 15. These figures describe the posted group summaries; they do not provide a formal estimate of the between-group difference.
The record does not clarify whether the medians are changes from baseline or measurements at a particular assessment. It also does not report a confidence interval, p-value, adjusted comparison, or other inferential result. Without those details, the precision of a treatment contrast and the compatibility of the data with different possible effects cannot be assessed. The interquartile ranges are not confidence intervals and should not be read as such.
Randomization is an important design feature in general because it aims to make groups comparable at allocation. The registry also identifies the study as single-masked. However, the procedures used to randomize and mask participants are not reported. The posted descriptions therefore do not permit an independent assessment of how those design protections were implemented.
The result does not establish that pioglitazone improves, worsens, or has no effect on AHI compared with placebo. It does not establish that the treatments are equivalent, since no equivalence analysis or precision estimate is reported. Nor can the descriptive summaries answer questions about effects on insulin resistance, insulin secretion, or CPAP, which are mentioned in the broader brief summary but are not represented by the posted primary AHI outcome.
The narrow interpretation is that the registry lists these AHI medians and interquartile ranges for the two groups at an 8-week timeframe. Stronger conclusions would require clarity about how the endpoint was calculated, who contributed data, and the statistical comparison and uncertainty estimates. Those details are not reported in the registry record.
13. Why This Trial Matters Statistically
This trial record illustrates why an outcome’s label and summary statistics need to be read together. The primary endpoint title refers to a change in AHI, but the record does not say whether the arm medians are changes from baseline or values at a specific assessment. Without that definition, the same numerical summary can be difficult to connect to the underlying clinical question.
It also demonstrates the distinction between describing groups and estimating a treatment effect. Medians and interquartile ranges show central tendency and spread, but they do not directly quantify the contrast between randomized groups or its precision. Reporting an effect estimate with an uncertainty interval would help readers assess both the size and the precision of a comparison. Such an inferential result is not reported in the registry record.
The group sizes differ: the outcome summaries list 30 participants for pioglitazone and 15 for placebo. Unequal group counts are not, by themselves, proof of a design problem. But the registry does not explain the reason for the difference or whether all randomized participants contributed outcome data. Clear accounting of participants assigned, measured, and analyzed is important for understanding attrition and the population represented by the result.
Finally, this record describes multiple related activities while posting one primary outcome and no analyses. Distinguishing the scope of a broad research program from the specific randomized comparison helps prevent readers from attributing findings from one activity to another. The statistical importance lies not in claiming a particular treatment result, but in identifying what the posted data can support and what remains uncertain.
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 outcome’s population field is blank, and the registry does not provide a detailed description of the participants contributing to the AHI summaries. The brief summary mentions overweight patients with OSA and participants considered at high risk of diabetes, but it does not specify the characteristics of the analyzed outcome groups. Generalizability to other patient groups cannot be assessed from the posted information.
The endpoint is titled as a change in AHI, but the record does not clarify whether the reported medians represent change scores or measurements at an assessment. Baseline AHI values, the method of calculating change, and the exact assessment procedure are not reported. This makes the clinical interpretation of the numerical summaries uncertain.
The registry gives no inferential comparison, confidence interval, p-value, model specification, or adjustment strategy. It also does not report missing-data handling, analysis-population definitions, exclusions, or the relationship between overall enrollment and outcome counts. These gaps prevent evaluation of the precision and robustness of the comparison.
The record identifies randomization and single masking but does not describe their implementation. It does not report the sample-size justification, multiplicity plan, interim analysis procedures, or a full statistical analysis plan. The broader summary includes other activities, including a separate CPAP intervention, but the relationship of those activities to the primary AHI outcome is not detailed. These limitations are specific to the information available in the registry record and do not establish that omitted procedures were absent from the study.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Obesity, Sleep Apnea, and Insulin Resistance — NCT02192684.
- Registry record last updated 2017-04-21; status last verified 2017-03.
- Results first posted 2017-04-21.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
NCT02192684 is a completed, randomized, single-masked, parallel-group study sponsored by Stanford University. The registry lists overall enrollment of 45, a start date of 2010-09, and primary completion in 2014-07. The primary outcome compares pioglitazone with placebo for AHI over 8 weeks and is specified as a median with interquartile range.
The reported pioglitazone summary is 35.8 events/hour, with an interquartile range of 21.0 to 49.0, among 30 participants. The placebo summary is 34.4 events/hour, with an interquartile range of 18.0 to 47.0, among 15 participants. The record does not clarify whether these values represent changes or measurements at an assessment, and it does not report an inferential comparison or confidence interval.
The registry lists zero serious adverse events in either group, other adverse events affecting 2 in the pioglitazone group and 0 in the placebo group, and no reported death counts. Missing-data procedures, analysis populations, and a trial-specific sample-size justification are not reported in the registry record.