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 Relationship Between Sleep and Glucose Tolerance in Prediabetes: the Role of GLP-1 in Short Sleepers (NCT02229487), a non-randomized na study. The primary outcome is GLP-1 Levels in Response to Oral Glucose Tolerance Test.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02229487 |
| Phase | NA |
| Condition | Prediabetes |
| Allocation | Non-Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 51 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Ramathibodi Hospital |
| Results posted | Yes |
2. Clinical Question
Population
People with prediabetes. The registry record separates participants according to objectively measured sleep duration. It describes normal sleep duration as 7-8 hours per night and short sleep duration as <6 hours per night. The record does not report further eligibility criteria or a demographic description of the population.
Intervention
The registry lists an oral glucose tolerance procedure as the intervention, classified as other. It describes measurement of GLP-1 levels in response to an oral glucose tolerance test. This is not a randomized treatment intervention: the comparison concerns sleep-duration groups.
Comparator
The comparator is the group with objectively measured normal sleep duration, compared with the group with short sleep duration. Because allocation was non-randomized, these groups should not be treated as if they were assigned to sleep durations under controlled conditions.
Primary question
The primary question is whether GLP-1 levels in response to an oral glucose tolerance test differ between people with prediabetes who have short sleep and those with normal sleep duration. The study summary also states hypotheses about glucose tolerance and a delayed or reduced GLP-1 response. Those hypotheses are not themselves results. The registry record does not report measured GLP-1 values or a between-group estimate, so it does not establish the direction or size of any observed difference.
3. Trial Design
The registry describes a completed, parallel, non-randomized study sponsored by Ramathibodi Hospital. It lists enrollment of 51 and identifies the condition as prediabetes. The study began in 2014-10, and primary completion is recorded as 2017-03. The phase is listed as NA. These administrative details describe the registered study; they do not provide evidence about the endpoint results.
The two groups are defined by objectively measured sleep duration. The normal-sleeper group is described as having 7-8 hours per night, and the short-sleeper group as having <6 hours per night. No random allocation is reported; allocation is explicitly listed as non-randomized. Masking is listed as none. The record therefore describes an observational group comparison rather than a blinded randomized comparison.
The intervention entry is oral glucose tolerance, classified as other. The primary outcome description says that people with and without short sleep undergo an oral glucose tolerance test with measurement of GLP-1 levels. The stated timeframe for that outcome is 2 weeks. The record does not explain the timing of that timeframe in relation to enrollment or testing, nor does it report a more detailed visit schedule.
Non-randomized groups can differ for reasons beyond the characteristic used to define them. Sleep duration may be associated with other measured or unmeasured characteristics, and those characteristics can complicate interpretation of a group contrast. The registry record does not report adjustment variables, matching, or another method intended to address such differences. It also does not report a detailed statistical analysis plan, recruitment procedures, or a sample-size justification. Those omissions limit what can be concluded about the design and analysis beyond the registry entries explicitly recorded.
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 | Normal Sleepers | Short Sleepers |
|---|---|---|
| STARTED | 24 | 27 |
| COMPLETED | 24 | 27 |
| 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 | Normal Sleeper | Short Sleeper | Total |
|---|---|---|---|---|
| Participants analysed | 24 | 27 | 51 | |
| Age, Continuous | years | 55.5 (SD 9.8) | 55.8 (SD 6.7) | 55.7 (SD 8.2) |
| Sex: Female, Male: Female | Participants | 19 | 20 | 39 |
| Sex: Female, Male: Male | Participants | 5 | 7 | 12 |
| Race/Ethnicity, Customized: Thai | Participants | 24 | 27 | 51 |
| Region of Enrollment: Thailand | Participants | 24 | 27 | 51 |
| BMI | kg/m^2 | 26.7 (SD 3.2) | 26.8 (SD 3.8) | 26.8 (SD 3.5) |
6. Primary Endpoint
The registry lists the primary outcome as GLP-1 Levels in Response to Oral Glucose Tolerance Test, measured over 2 weeks.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | pmol/l.h |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is GLP-1 levels in response to an oral glucose tolerance test, reported with the unit pmol/l.h. The registry specifies a median as the summary parameter and an inter-quartile range as the measure of dispersion. Its description says GLP-1 levels are measured in people with and without short sleep, and gives a timeframe of 2 weeks.
GLP-1 is the biological measure named in the endpoint. A response measured during an oral glucose tolerance test can characterize how the measured signal changes in the context of that test. The study summary proposes that short sleepers may have a delayed or reduced response, but the endpoint description alone does not show whether such a pattern occurred. The record does not specify the exact sampling schedule, the calculation used to derive the endpoint, or the definition of a delayed response.
General statistical context: a median describes the middle of an observed distribution and is less sensitive to extreme values than a mean. The inter-quartile range describes the spread of the central portion of the observations. Reporting these summaries can be useful when a distribution is skewed or contains outlying values. Neither summary, on its own, quantifies the uncertainty in a comparison between groups. The registry record does not report the group medians, inter-quartile ranges, or a comparative estimate for this endpoint.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a primary endpoint and its planned summary format, but it does not report the observed endpoint values. No group median, inter-quartile range, between-group estimate, confidence interval, or test result is reported in the registry record. The direction and magnitude of the observed GLP-1 response therefore cannot be described from this record. The hypotheses in the study summary are questions the study was intended to address, not evidence that either hypothesis was confirmed.
The intended comparison is between people with prediabetes classified by objectively measured sleep duration. That classification is not randomized. A difference between the groups, if reported, would describe an association in the studied groups; it would not by itself establish that sleep duration caused the difference. People in the groups could differ in other ways that affect glucose tolerance or GLP-1 response. The registry record does not report whether those characteristics were measured or adjusted for.
Precision also cannot be judged from the registered endpoint description. General statistical context: a confidence interval expresses a range of values compatible with the data and the method used to calculate it. A narrow interval generally indicates more precision than a wide interval, while an interval that spans values representing materially different effects leaves greater uncertainty. No confidence interval is reported for the primary endpoint in the registry record, so the precision of any group contrast cannot be assessed.
The enrollment entry is 51. The record does not state how many participants contributed usable primary-endpoint data, whether all enrolled participants underwent the test, or whether any measurements were excluded. Consequently, the enrollment entry alone cannot establish the effective analysis size. The endpoint timeframe is recorded as 2 weeks, but the record does not provide enough detail to interpret the timing of endpoint collection beyond that notation.
The registry lists one outcome measure and one analysis, but this count does not reveal the analysis method or the completeness of reporting. No statistical test, adjustment strategy, missing-data method, or analysis population is described. Without these details and the endpoint results, the record supports a description of the research question and design, not a conclusion about whether the groups differed. The findings should not be inferred from the stated hypotheses, enrollment, or safety counts.
9. Statistical Methods Explained
General statistical context: the design determines what a comparison can support. This study is registered as non-randomized and parallel. A parallel design compares separate groups rather than following a crossover in which participants receive each condition. Here the groups are defined by sleep duration, not assigned at random to different sleep durations. A comparison can therefore describe how the measured outcome differs across those groups, but group differences may reflect factors other than sleep duration. The registry record does not report an adjustment plan or other method for addressing confounding.
What does non-randomized allocation imply?
Randomization, when used, aims to make treatment groups comparable in expectation with respect to both measured and unmeasured characteristics. That protection is not available from the registered design. Objective measurement of sleep duration describes how the groups were categorized, but it does not make the groups exchangeable. General statistical context: confounding occurs when another characteristic is associated with both the exposure or group membership and the outcome, potentially distorting the group contrast. Whether particular confounders were present or addressed is not reported in the registry record.
How should the endpoint summaries be read?
The primary outcome is summarized using a median and inter-quartile range. General statistical context: the median is the central observation after values are ordered, while the inter-quartile range characterizes spread across the middle half of the distribution. These are descriptive summaries. A difference between medians, if reported, would not automatically be the estimated difference in every aspect of the distributions. The registry record does not provide the medians or inter-quartile ranges, and it does not describe the comparison statistic or inferential method.
The endpoint unit is pmol/l.h. The record names GLP-1 levels in response to an oral glucose tolerance test, but does not explain the derivation of the reported endpoint or its sampling schedule. It would be inappropriate to assume a particular summary of repeated measurements, such as an area-under-the-curve calculation, without that information. The timeframe is recorded as 2 weeks, but how that timeframe maps onto the test and measurement schedule is not reported in the registry record.
What would uncertainty measures add?
General statistical context: an estimate describes the observed contrast, whereas a confidence interval communicates uncertainty around that estimate under the chosen analysis assumptions. A p-value, when used, describes how compatible the observed data are with a specified null model; it is not the probability that the null hypothesis is true, and it does not measure clinical importance. The registry record does not report a confidence interval or p-value for the primary outcome. It also does not identify the statistical test, model, or significance threshold used for the endpoint analysis.
The record's sample-size assumptions describe planning illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The illustrated effect is defined as a stated fraction of the observed effect. General statistical context: such calculations estimate the number of participants per arm needed under their assumptions to detect a specified effect with a chosen power. They are planning illustrations, not observed power and not evidence that the study had a particular probability of detecting its true effect. The record does not report the study's own sample-size justification. The actual illustration values are not reported in the registry record.
Those planning assumptions also require care in this setting. Equal allocation is an assumption for the illustration, not proof that the observed groups were equally sized. A normal approximation is a calculation choice, not a description of the observed endpoint distribution. If the observed effect is used as the basis for planning, the resulting illustration inherits uncertainty from that estimate. The registry record does not provide enough detail to assess those calculations or to determine whether they reproduce a prespecified design target.
Why can distribution shape matter?
General statistical context: over-dispersion means that variability is greater than a statistical model expects. If a model assumes less variability than is present, standard errors may be too small and uncertainty may be understated. Conversely, an analysis that does not fit the distribution may give misleading estimates or intervals. The endpoint is summarized by median and inter-quartile range, but no distributional assessment or model is reported in the registry record. It is therefore not possible to evaluate whether a particular model fit the measured values.
Likewise, a single summary can conceal patterns over time. The study summary raises the possibility of a delayed or reduced GLP-1 response, while the primary outcome is described as GLP-1 levels in response to the test. To distinguish response timing from response magnitude, an analysis would need measurements and a method suited to that question. Sampling details and the corresponding analysis are not reported in the registry record. No conclusion about delayed response can be drawn from the endpoint title alone.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists one outcome measure and one analysis. It does not state whether other outcomes or analyses were conducted but not entered, whether the primary outcome was selected before examining the data, or whether any multiplicity adjustment was planned. A count of registered outcomes and analyses does not, by itself, establish the full set of statistical comparisons performed.
General statistical context: when many outcomes, time points, subgroups, or statistical tests are examined, the chance of obtaining an apparently notable result by chance can increase. Multiplicity procedures can control particular error rates, but their appropriateness depends on the questions and analysis plan. No multiplicity procedure is reported in the registry record. Because endpoint results and analysis details are also absent, the potential impact of multiple testing cannot be assessed.
Missing-data handling is not reported in the registry record. The record does not say whether any GLP-1 measurements were unavailable, how missing measurements were handled, or whether exclusions were made. It also does not report whether the analysis included all enrolled participants or a defined subset. The enrollment entry is 51, but enrollment is not necessarily the same as the number contributing to a particular endpoint analysis.
The analysis population is not reported in the registry record. There is no description of eligibility for the endpoint analysis, handling of participants who did not complete testing, or rules for excluding observations. Without these details, readers cannot determine how the analyzed participants relate to the enrolled population or assess the risk that missingness or selection affected the 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 |
|---|---|---|---|
| Normal Sleeper | 0 | 24 | 0.0% |
| Short Sleeper | 0 | 27 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Normal Sleeper | 0 of 24 |
| Short Sleeper | 0 of 27 |
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 |
|---|---|
| Normal Sleeper | 0 of 24 |
| Short Sleeper | 0 of 27 |
The registry safety record lists a normal-sleeper group with 24 at risk and a short-sleeper group with 27 at risk. In each group, the recorded counts are zero for affected participants with serious adverse events, zero for affected participants with other adverse events, and zero deaths. These are the registry's reported counts, not estimates of comparative safety.
General statistical context: a count of zero recorded events does not establish that an event is impossible or that risks are identical between groups. Interpretation depends on how events were defined, collected, and followed, and on the amount of observation available. The registry record does not report further event definitions, event-collection procedures, or follow-up details. It also does not list serious adverse-event terms.
The at-risk counts are the denominators associated with the safety entries. They should not be treated as proof that every participant completed the primary endpoint or had the same duration of safety observation. Safety counts do not supply information about the GLP-1 outcome, and they cannot substitute for its unreported results.
12. What the Result Does, and Does Not, Mean
The record identifies a focused physiological question: whether GLP-1 levels in response to an oral glucose tolerance test differ between people with prediabetes classified as short sleepers and those classified as normal sleepers. It also records hypotheses concerning glucose tolerance and the timing or size of the GLP-1 response. These statements clarify the motivation for the comparison; they do not establish what the measurements showed.
The record does not report primary endpoint values or a statistical comparison. It therefore does not support a statement that one group had higher or lower GLP-1 levels, a delayed response, or a difference in glucose tolerance. It also does not permit an assessment of the magnitude or precision of a group contrast. Those results are not reported in the registry record.
Even if a difference were available, the non-randomized design would limit causal interpretation. People were grouped by objectively measured sleep duration rather than randomly assigned to sleep-duration categories. Differences could reflect other characteristics of the groups. The registry record does not describe adjustment for potential confounders, so it is not possible to determine how such factors were handled.
General statistical context: statistical evidence and practical importance are distinct. A result can be estimated precisely yet be small in practical terms, or be uncertain even when its point estimate appears substantial. Interpretation requires the estimate, its uncertainty, the measurement context, and a defensible analysis. None of those endpoint result details is reported in the registry record.
The safety entries are limited to the event counts recorded for the groups. They do not answer the primary biological question or establish comparative safety. Overall, the registry record describes the design, endpoint, and stated hypotheses, but does not report outcome findings that would resolve those hypotheses.
13. Why This Trial Matters Statistically
This study is statistically informative as an example of how a carefully defined exposure can still lead to a non-randomized comparison. Sleep duration was measured objectively and used to distinguish the groups, which makes the group definition explicit. However, objective measurement of the grouping variable does not remove the possibility that the groups differ in other factors related to GLP-1 response or glucose tolerance.
The endpoint also raises a measurement and analysis question. A response to an oral glucose tolerance test may involve measurements taken in relation to the test, while the registry lists a median and inter-quartile range for the primary outcome. Clear reporting of measurement timing and the construction of the endpoint is important for understanding whether the analysis addresses response magnitude, timing, or both. Those details are not reported in the registry record.
The record illustrates why hypotheses, design details, and results must be read separately. The study summary proposes expected differences, but the registry record does not report measured endpoint results. The enrollment entry and the safety counts do not reveal the direction or precision of the primary comparison. Without effect estimates and uncertainty measures, readers cannot judge how much information the study contributes to the stated question.
Finally, planning calculations and observed findings have different purposes. The record describes sample-size illustrations based on an observed effect and specified planning assumptions. Such illustrations can help frame future study planning, but they are not observed power and do not replace transparent reporting of the study's endpoint estimates, analysis population, and missing-data handling. These distinctions matter when interpreting registry records across clinical research.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The main limitation for interpretation is that the registry record does not report primary endpoint results. Group medians, inter-quartile ranges, a comparative estimate, and measures of uncertainty are absent. The stated hypotheses therefore cannot be evaluated using the registered outcome information.
The non-randomized allocation limits causal interpretation. Group membership is based on objectively measured sleep duration, but the record does not report whether potentially relevant characteristics were measured or adjusted for. As a result, any observed group difference, if one exists, could not be attributed to sleep duration solely on the basis of this design description.
The outcome description leaves important measurement details unspecified. The record names GLP-1 levels in response to an oral glucose tolerance test, gives the unit pmol/l.h, and records a timeframe of 2 weeks. It does not report the sampling schedule, endpoint derivation, or the specific analysis used to evaluate response timing or magnitude.
Other important analysis details are not reported in the registry record, including the analysis population, handling of missing measurements, statistical model or test, and any adjustment for multiplicity. The enrollment entry does not identify how many participants contributed data to the primary endpoint. The record also does not report a sample-size justification for the study itself; the described planning illustrations are not a substitute for one.
These limitations concern what can be learned from the registry record. They do not establish that the study lacked procedures or analyses that were not recorded. Rather, those procedures and results are not reported in the registry record, so their adequacy cannot be assessed.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: The Relationship Between Sleep and Glucose Tolerance in Prediabetes: the Role of GLP-1 in Short Sleepers — NCT02229487.
- Registry record last updated 2017-10-10; status last verified 2017-09.
- Results first posted 2017-08-14.
- 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
The registry record describes a completed, non-randomized, parallel study sponsored by Ramathibodi Hospital. It lists enrollment of 51 and the condition as prediabetes. Sleep groups are defined using objective measurement: normal sleep duration is 7-8 hours per night, and short sleep duration is <6 hours per night. Masking is listed as none, and phase as NA.
The primary outcome is GLP-1 levels in response to an oral glucose tolerance test, summarized by median and inter-quartile range, with a timeframe of 2 weeks and unit pmol/l.h. The record lists one outcome measure and one analysis, but does not report the primary endpoint findings or the analysis methods needed to interpret a group comparison.
Safety entries list zero affected participants with serious adverse events, zero with other adverse events, and zero deaths in each group. These counts do not provide primary endpoint results. Overall, the record describes the research question and design but does not report findings that resolve the stated hypotheses.