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 Phase IIB 2-Period Crossover Polysomnography Study in Participants With Primary Insomnia (MK-4305-006) (NCT00792298), a randomized phase 2 study. The primary outcome is LS Mean Sleep Efficiency (SE) During Periods 1 and 2.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00792298 |
| Phase | Phase 2 |
| Condition | Primary Insomnia |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | Double |
| Enrollment | 254 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Merck Sharp & Dohme LLC |
| Results posted | Yes |
2. Clinical Question
Population
The study enrolled participants with primary insomnia. The registry records an enrollment of 254. The Full Analysis Set included randomized participants who received at least one dose of study medication and had post-randomization efficacy assessment data; its composition could vary by endpoint because of missing data. The record does not provide further eligibility details in the information available for this analysis.
Intervention
The intervention was suvorexant, also identified as MK-4305, taken daily before bedtime. The sequences included suvorexant 10 mg, 20 mg, 40 mg, or 80 mg during one treatment period and dose-matched placebo during the other. Each period included 4 weeks of treatment.
Comparator
The comparator was dose-matched placebo. This was a crossover comparison: participants followed a sequence in which suvorexant and placebo were taken in separate periods, with a single-blind placebo washout period between them. Thus, the study was designed to compare treatment conditions within a crossover framework rather than as a simple parallel-group trial.
Primary question
The primary question concerned sleep efficiency during Periods 1 and 2, measured on Night 1 and at the end of Week 4. Sleep efficiency was defined as total sleep time divided by time in bed, expressed as a percentage. The registry record identifies this outcome but does not report the numerical treatment estimates or a statistical comparison for it.
3. Trial Design
This Phase II study was randomized, double-blind, placebo-controlled, multicenter, and used a two-period crossover design. Participants were assigned to sequences that placed suvorexant and dose-matched placebo in different treatment periods. The listed sequences paired placebo with suvorexant at 10 mg, 20 mg, 40 mg, or 80 mg, with the order reversed across sequences. The registry records an enrollment of 254.
Before treatment, the sequence descriptions specify an approximately 1- to 2-week single-blind placebo run-in. In Period 1, participants received their assigned study treatment daily before bedtime for 4 weeks. A 1-week single-blind placebo washout followed, after which the sequence switched to the other treatment for Period 2. The descriptions available in the registry record are truncated, so further details of the second treatment period are not reported in the registry record.
In a crossover design, each participant can contribute measurements under more than one treatment condition. This can support comparisons that account for within-participant variation, but it also makes the analysis dependent on design features such as treatment sequence, period, and possible carryover. Which of these features was included in the statistical model is not reported in the registry record. Randomization and double blinding describe allocation and masking, but do not by themselves establish how the analysis handled the paired measurements.
The primary outcome was least-squares mean sleep efficiency during the two treatment periods, assessed on Night 1 and at the end of Week 4. Wake after persistent sleep onset and latency to the onset of persistent sleep were listed as secondary outcomes. The record states that there were 4 outcome measures and 32 analyses, but numerical efficacy estimates and inferential results are not reported in the registry record. The study is listed as completed; its start date was 2008-11-05 and its primary completion date was 2009-12-26.
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.
Only the first 6 of 8 groups are shown.
Treatment Period 1
| Stage | Suvorexant 10 mg → Placebo | Placebo → Suvorexant 10 mg | Suvorexant 20 mg → Placebo | Placebo → Suvorexant 20 mg | Suvorexant 40 mg → Placebo | Placebo → Suvorexant 40 mg |
|---|---|---|---|---|---|---|
| STARTED | 31 | 32 | 33 | 32 | 32 | 32 |
| COMPLETED | 30 | 31 | 31 | 28 | 32 | 29 |
| NOT COMPLETED | 1 | 1 | 2 | 4 | 0 | 3 |
Reasons for not completing this period:
| Reason | Suvorexant 10 mg → Placebo | Placebo → Suvorexant 10 mg | Suvorexant 20 mg → Placebo | Placebo → Suvorexant 20 mg | Suvorexant 40 mg → Placebo | Placebo → Suvorexant 40 mg |
|---|---|---|---|---|---|---|
| Adverse Event | 0 | 1 | 0 | 1 | 0 | 1 |
| Lack of Efficacy | 0 | 0 | 1 | 0 | 0 | 0 |
| Withdrawal by Subject | 1 | 0 | 1 | 2 | 0 | 2 |
| Lost to Follow-up | 0 | 0 | 0 | 0 | 0 | 0 |
| Physician Decision | 0 | 0 | 0 | 1 | 0 | 0 |
| Protocol Violation | 0 | 0 | 0 | 0 | 0 | 0 |
Washout
| Stage | Suvorexant 10 mg → Placebo | Placebo → Suvorexant 10 mg | Suvorexant 20 mg → Placebo | Placebo → Suvorexant 20 mg | Suvorexant 40 mg → Placebo | Placebo → Suvorexant 40 mg |
|---|---|---|---|---|---|---|
| STARTED | 30 | 31 | 32 | 28 | 32 | 29 |
| COMPLETED | 30 | 31 | 31 | 28 | 32 | 27 |
| NOT COMPLETED | 0 | 0 | 1 | 0 | 0 | 2 |
Reasons for not completing this period:
| Reason | Suvorexant 10 mg → Placebo | Placebo → Suvorexant 10 mg | Suvorexant 20 mg → Placebo | Placebo → Suvorexant 20 mg | Suvorexant 40 mg → Placebo | Placebo → Suvorexant 40 mg |
|---|---|---|---|---|---|---|
| Adverse Event | 0 | 0 | 0 | 0 | 0 | 1 |
| Withdrawal by Subject | 0 | 0 | 1 | 0 | 0 | 1 |
Treatment Period 2
| Stage | Suvorexant 10 mg → Placebo | Placebo → Suvorexant 10 mg | Suvorexant 20 mg → Placebo | Placebo → Suvorexant 20 mg | Suvorexant 40 mg → Placebo | Placebo → Suvorexant 40 mg |
|---|---|---|---|---|---|---|
| STARTED | 30 | 31 | 31 | 28 | 32 | 27 |
| COMPLETED | 29 | 30 | 30 | 26 | 30 | 27 |
| NOT COMPLETED | 1 | 1 | 1 | 2 | 2 | 0 |
Reasons for not completing this period:
| Reason | Suvorexant 10 mg → Placebo | Placebo → Suvorexant 10 mg | Suvorexant 20 mg → Placebo | Placebo → Suvorexant 20 mg | Suvorexant 40 mg → Placebo | Placebo → Suvorexant 40 mg |
|---|---|---|---|---|---|---|
| Lack of Efficacy | 0 | 0 | 0 | 0 | 1 | 0 |
| Physician Decision | 0 | 0 | 0 | 0 | 0 | 0 |
| Pregnancy | 0 | 0 | 1 | 0 | 0 | 0 |
| Withdrawal by Subject | 1 | 1 | 0 | 2 | 1 | 0 |
Analysis population for the primary outcome, as defined in the registry: Full Analysis Set (FAS) population; subset of all randomized participants who received at least one dose of study medication and had any post-randomization efficacy assessment data. The FAS population may have varied across endpoints due to the degree of missing data for each endpoint.
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 | All Treated Participants |
|---|---|---|
| Participants analysed | 254 | |
| Age, Continuous | years | 44.4 (SD 11.5) |
| Sex: Female, Male: Female | Participants | 148 |
| Sex: Female, Male: Male | Participants | 106 |
6. Primary Endpoint
The registry lists the primary outcome as LS Mean Sleep Efficiency (SE) During Periods 1 and 2, measured over Night 1 and end of Week 4.
| Element | Registry entry |
|---|---|
| Result type | Least Squares Mean |
| Measure of spread | Standard Error |
| Unit | percent of time in bed |
| Endpoint classification | Continuous Endpoint |
The primary endpoint was least-squares mean sleep efficiency, reported as a percent of time in bed, during Periods 1 and 2. The specified assessment times were Night 1 and the end of Week 4. Sleep efficiency was defined as total sleep time divided by time in bed, multiplied by 100. Total sleep time included time spent in Stages 1, 2, 3, and 4 and rapid eye movement sleep. Time in bed was measured from lights off to lights on and was fixed at 8 hours on each polysomnography night.
As a continuous measure, sleep efficiency represents the share of the specified time-in-bed interval spent asleep. General: continuous outcomes retain the magnitude of measurements rather than reducing them to categories such as improved or not improved. That can make treatment contrasts interpretable in the measurement scale, while the clinical importance of a difference still depends on context and is not established by the scale alone.
The endpoint is based on polysomnography, an objective recording of sleep during the specified nights. That measurement definition explains what the endpoint represents; it does not establish how the treatment groups differed. The registry record does not report least-squares mean values, standard errors, confidence intervals, or hypothesis-test results for sleep efficiency. The posted results therefore do not allow a numerical estimate of the treatment contrast or its precision to be described.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies sleep efficiency as the primary outcome and gives its definition, unit, and assessment times. It does not report numerical results for this endpoint. No treatment-specific least-squares means, treatment contrast, standard errors, confidence intervals, or p-values are reported in the registry record. Consequently, the posted results do not establish the direction, size, or precision of a sleep-efficiency difference between suvorexant and placebo.
The same limitation applies to the listed secondary outcomes: least-squares mean wake after persistent sleep onset and latency to the onset of persistent sleep during Periods 1 and 2. Their titles are recorded, but their numerical findings are not reported in the registry record. A name or definition for an outcome is not evidence of the observed result for that outcome.
General: a treatment estimate describes the observed contrast on an outcome scale, while a confidence interval describes the range of values compatible with the estimate and the analysis assumptions. A narrow interval indicates greater statistical precision than a wide interval, but precision is not the same as clinical importance. Without the estimate and uncertainty interval, neither the size of a possible contrast nor how precisely it was estimated can be assessed. A missing p-value also means that a threshold-based inference cannot be reconstructed from the registry record.
The crossover structure deserves attention when interpreting any treatment comparison. Measurements from the same participant are generally related, so a sound analysis needs to reflect that within-participant relationship. Period and sequence can also matter in a crossover trial. Which model terms or covariance assumptions were used is not reported in the registry record. It is therefore not possible to assess whether the posted analysis accounted for those features, or to independently reproduce the sponsor’s analysis.
The record states that 4 outcome measures and 32 analyses were registered. Multiple outcomes, time points, and comparisons can create multiplicity: when many statistical tests are considered, the chance of at least one apparently notable result can increase. The registry record does not report a multiplicity strategy, a hierarchy of tests, or which analysis was designated for each reported comparison. The existence of many analyses alone does not show that any particular finding is false, but it makes the analysis plan important for interpretation.
The reported enrollment is 254, but this is not necessarily the number contributing data to every endpoint. The Full Analysis Set is defined by receipt of at least one dose and availability of post-randomization efficacy data, and its size could vary across endpoints because of missing observations. Endpoint-specific analysis counts and reasons for missingness are not reported in the registry record. The enrollment figure therefore cannot substitute for an endpoint-specific denominator.
Safety information is reported separately from efficacy. The record lists no serious adverse events in the listed treatment groups, while it reports other adverse event counts that differ by group. Those counts describe events as tabulated in the registry; they do not supply a detailed event narrative, exposure-adjusted rate, or statistical comparison. The death fields are not populated, so deaths are not reported in the registry record.
9. Statistical Methods Explained
The registry describes the primary continuous endpoint as a least-squares mean with standard error. These terms characterize a type of summary and its uncertainty, but the numerical estimates are not reported in the registry record. The distinction between an outcome definition and an outcome result is essential: the former tells the reader what was measured; the latter would show what values were observed and how treatments compared.
What is a least-squares mean?
General: a least-squares mean is an estimate produced by a statistical model. It is often called a model-based or adjusted mean because it can account for factors included in that model. The meaning of the adjustment depends on the variables and assumptions specified. The registry record identifies the parameter as a least-squares mean but does not report the model specification or the factors used to obtain it. It is therefore not possible to say which adjustments were made or to reproduce the estimate.
In a crossover study, the same participant may have measurements under both treatment conditions. General: such observations are correlated because measurements from one person tend to share participant-specific characteristics. Analyses that treat correlated observations as though they were independent can misstate uncertainty. A crossover analysis may model participant-level variation and account for treatment and period, among other design features. The registry record does not report which approach was used, so those details should not be inferred from the trial design alone.
What does the standard error describe?
General: a standard error describes the statistical uncertainty of an estimated quantity under the analysis model. It is not the spread of individual participant values. A confidence interval is commonly formed using an estimate and its standard error, together with a method for selecting the interval limits. A larger standard error generally corresponds to less precision, all else being equal. Here, the record names standard error as the dispersion measure but gives no numerical standard errors or confidence intervals for the primary outcome.
Because the endpoint is continuous, a treatment contrast would ordinarily be expressed in the endpoint’s own scale, which is percent of time in bed. General: that contrast would describe the difference in model-based sleep-efficiency estimates between treatment conditions, subject to the chosen model and analysis population. No such contrast is reported in the registry record, so no magnitude or direction can be stated.
Why do crossover features matter?
General: crossover studies can be efficient because participants serve as their own comparison, reducing the influence of characteristics that remain stable within a person. The design also introduces considerations that are less central in a parallel-group comparison. Measurements may depend on period, treatment order, or residual effects from an earlier treatment. A washout period is intended to separate treatment periods, but the existence of a washout does not itself establish that carryover was absent. The registry specifies a 1-week single-blind placebo washout; whether carryover was assessed and how period or sequence was handled are not reported in the registry record.
The trial description identifies randomization and double blinding. Randomization concerns assignment to treatment sequence, while blinding concerns knowledge of treatment assignment. These design features can reduce certain biases, but they do not replace details of the analytic model, missing-data handling, or outcome reporting. The registry record does not provide those details sufficiently to evaluate every analytical assumption.
What can be inferred from the analysis counts?
The record lists 4 outcome measures and 32 analyses. General: multiple analyses may reflect multiple outcomes, time points, treatment contrasts, or other analytic choices. When many tests are conducted, unadjusted significance tests can increase the chance of at least one false-positive finding across the family of tests. Methods such as a prespecified hierarchy or multiplicity adjustment can address some of this concern, but the method must be known before the implications can be judged. A multiplicity plan is not reported in the registry record.
The record also describes planning illustrations based on a fraction of an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. These are planning assumptions, not observed trial outcomes or observed power. The record says that non-time-to-event illustrations express participants per arm. Numerical illustration results are not reported in the registry record, and they should not be mistaken for the actual allocation or enrollment of this crossover study.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists 4 outcome measures and 32 analyses. It does not report how the analyses were organized into families of hypotheses, whether one endpoint or time point had priority, or whether any adjustment for multiple testing was applied. General: examining multiple outcomes or comparisons can increase the chance of an apparently unusual result by chance alone. A prespecified hierarchy, adjustment procedure, or clearly designated primary comparison can help readers understand how that issue was addressed. Without a reported strategy, the effect of multiplicity on inferential claims cannot be evaluated.
The primary endpoint is identified as sleep efficiency during Periods 1 and 2, with assessments on Night 1 and at the end of Week 4. The record also lists wake after persistent sleep onset and latency to the onset of persistent sleep as secondary outcomes. It does not report which time point or contrast, if any, governed the statistical conclusion, nor does it provide numerical estimates or test results for these outcomes.
The Full Analysis Set included randomized participants who received at least one dose of study medication and had any post-randomization efficacy assessment data. The record notes that this population may vary across endpoints because of missing data. Endpoint-specific denominators, the amount and pattern of missing data, reasons for missingness, and the method used to handle missing observations are not reported in the registry record. These omissions prevent assessment of whether missingness could have influenced the endpoint estimates.
General: missing data can affect both the precision and validity of an estimate, particularly when the likelihood of a missing measurement is related to the outcome or treatment. Analyses may use different assumptions or sensitivity checks, and those choices should be reported to judge robustness. The registry record does not describe such methods or sensitivity analyses.
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 |
|---|---|---|---|
| Placebo | 0 | 249 | 0.0% |
| Suvorexant 10 mg | 0 | 62 | 0.0% |
| Suvorexant 20 mg | 0 | 61 | 0.0% |
| Suvorexant 40 mg | 0 | 59 | 0.0% |
| Suvorexant 80 mg | 0 | 61 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Placebo | 9 of 249 |
| Suvorexant 10 mg | 1 of 62 |
| Suvorexant 20 mg | 4 of 61 |
| Suvorexant 40 mg | 11 of 59 |
| Suvorexant 80 mg | 11 of 61 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Placebo | Suvorexant 10 mg | Suvorexant 20 mg | Suvorexant 40 mg | Suvorexant 80 mg |
|---|---|---|---|---|---|---|
| Somnolence | Nervous system disorders | 1 of 249 | 1 of 62 | 3 of 61 | 7 of 59 | 7 of 61 |
| Headache | Nervous system disorders | 6 of 249 | 0 of 62 | 1 of 61 | 3 of 59 | 3 of 61 |
| Urinary tract infection | Infections and infestations | 2 of 249 | 0 of 62 | 0 of 61 | 3 of 59 | 2 of 61 |
The registry lists serious adverse event counts of 0 for placebo, suvorexant 10 mg, suvorexant 20 mg, suvorexant 40 mg, and suvorexant 80 mg. It also lists 9 other adverse events for placebo, 1 for suvorexant 10 mg, 4 for suvorexant 20 mg, 11 for suvorexant 40 mg, and 11 for suvorexant 80 mg. These are event counts as recorded, not percentages or comparisons adjusted for exposure.
The listed numbers at risk are 249 for placebo, 62 for suvorexant 10 mg, 61 for suvorexant 20 mg, 59 for suvorexant 40 mg, and 61 for suvorexant 80 mg. Because the trial used a crossover design, participants could contribute experience under more than one treatment condition; the group counts should not be added to infer a count of distinct participants. The record does not explain the exposure or counting rules behind these safety denominators in further detail.
The serious adverse event terms list is empty. The death fields are not populated, so deaths are not reported in the registry record. The adverse event counts do not provide event descriptions, severity gradings for the other events, exposure duration by treatment, or statistical comparisons. They should therefore be read as registry tabulations rather than as evidence of a treatment effect or a complete assessment of comparative safety.
12. What the Result Does, and Does Not, Mean
The registry record establishes the study question and design: a randomized, double-blind, placebo-controlled crossover evaluation of suvorexant in participants with primary insomnia. It identifies sleep efficiency as the primary outcome and describes how that measure was defined using polysomnography. It also documents the treatment sequences and lists secondary sleep outcomes. These details explain what the trial set out to assess.
The record does not report numerical efficacy findings. There is no reported primary outcome estimate, treatment contrast, standard error, confidence interval, or p-value. As a result, the direction and size of the sleep-efficiency comparison cannot be described, and the precision of any estimate cannot be assessed. The same gap applies to the listed secondary outcomes. The absence of results in the registry record is not evidence that treatments were equivalent, nor does it establish that one treatment was better.
General: statistical evidence and clinical importance are distinct questions. An estimate and its uncertainty help characterize the range of effects compatible with the data and model; clinical interpretation also requires context about what differences matter. Neither question can be answered from an outcome definition alone. In this case, numerical estimates and their uncertainty are not reported in the registry record.
The safety record reports zero serious adverse events in each listed group and reports other adverse event counts by treatment group. These figures are descriptive registry counts. The record does not report detailed event terms for the non-serious category, exposure-adjusted comparisons, or a statistical analysis of safety differences. The death information is not populated. The tabulations therefore do not support a comprehensive comparison of safety outcomes.
Enrollment of 254 describes the trial’s recorded enrollment, not the number of observations available for every outcome. The Full Analysis Set definition requires dosing and post-randomization efficacy data, and the record notes that this population could vary by endpoint. Without endpoint-specific counts and missing-data information, the precision and representativeness of any endpoint analysis cannot be evaluated.
Overall, the posted information supports a description of the trial’s design, endpoint definitions, analysis population criteria, and selected safety counts. It does not support a conclusion about the magnitude or certainty of efficacy differences, or a definitive comparative safety conclusion.
13. Why This Trial Matters Statistically
This study is statistically notable for its crossover design and repeated sleep measurements. In a crossover study, participants receive treatment conditions in sequence, so the analysis must respect the relationship between measurements from the same person. That structure can offer a useful within-participant comparison, but it also makes period, sequence, and possible carryover relevant to interpretation. The registry record describes the sequence and washout but does not report how the statistical analysis addressed those features.
The endpoint is defined in a concrete measurement scale: sleep efficiency is a percentage based on total sleep time relative to time in bed, measured by polysomnography. Its definition and assessment timing make clear what was intended to be compared. Yet the absence of numerical outcome results is a central statistical limitation: without estimates and uncertainty, neither the magnitude nor precision of a treatment contrast can be assessed.
The record also lists several outcome measures and analyses. That makes transparent reporting of the prespecified outcome hierarchy and multiplicity approach especially relevant. The number of analyses alone does not tell whether multiplicity was controlled, which comparisons were primary, or how findings should be interpreted. Those details are not reported in the registry record.
Finally, the stated Full Analysis Set criteria and acknowledgment that its composition can vary by endpoint highlight an important distinction between enrolled participants and participants contributing to a particular analysis. Endpoint-specific denominators and missing-data methods matter for judging how much information supports an estimate. They are not reported in the registry record. Thus, the trial record is informative about design and measurement but limited for evaluating the statistical results themselves.
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 interpreting this trial is that numerical efficacy results are not reported in the registry record. Although the primary endpoint is identified and defined, there are no reported least-squares means, treatment contrasts, standard errors, confidence intervals, or test results. The listed secondary outcomes likewise lack numerical findings. This prevents assessment of effect direction, magnitude, and precision.
The registry describes the crossover sequence and a 1-week placebo washout, but does not report the statistical model, treatment of period or sequence effects, handling of within-participant correlation, or assessment of carryover. Without these methods, the analysis cannot be independently appraised in relation to the design.
Missing-data reporting is also limited. The Full Analysis Set definition permits variation across endpoints, but endpoint-specific participant counts, reasons for missingness, and methods for addressing missing observations are not reported in the registry record. The record also lists 4 outcome measures and 32 analyses without reporting a multiplicity plan or the hierarchy of comparisons.
The safety tabulation includes group counts but does not provide detailed descriptions of other adverse events, exposure-adjusted rates, or statistical comparisons. Death fields are not populated. In addition, the arm descriptions are truncated, limiting the available detail about the later portion of each sequence. These limitations restrict interpretation to the recorded design, endpoint definitions, and listed safety counts; they do not resolve the missing efficacy findings.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Phase IIB 2-Period Crossover Polysomnography Study in Participants With Primary Insomnia (MK-4305-006) — NCT00792298.
- Registry record last updated 2018-11-06; status last verified 2018-10.
- Results first posted 2014-11-14.
- 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.
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18. Record Summary
NCT00792298 is a completed Phase II randomized, double-blind, placebo-controlled, multicenter crossover study of suvorexant in participants with primary insomnia. The registry records enrollment of 254. Participants followed sequences involving suvorexant 10 mg, 20 mg, 40 mg, or 80 mg and dose-matched placebo, with a placebo run-in, 4-week treatment periods, and a 1-week placebo washout.
The primary endpoint was least-squares mean sleep efficiency during Periods 1 and 2, assessed on Night 1 and at the end of Week 4. The registry record does not report numerical efficacy findings, analysis-model details, a multiplicity strategy, or endpoint-specific missing-data information. Safety tabulations list 0 serious adverse events in each group and other adverse event counts by group; death information is not reported in the registry record.