Characteristics of Sleep Patterns in Young Adults With and Without Insomnia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Characteristics of Sleep Patterns in Young Adults With and Without Insomnia (NCT00177216), a randomized phase 4 study. The primary outcome is Change in Pittsburgh Sleep Quality Index.

2. Clinical Question

3. Trial Design

The registry identifies NCT00177216 as a completed Phase 4, randomized, triple-masked, parallel-group study sponsored by the University of Pittsburgh. Its listed enrollment is 69. The registry gives a study start of 2002-02 and a primary completion date of 2008-05. The brief summary describes comparisons of symptoms, experiences and laboratory sleep characteristics in young adults with and without insomnia. The posted primary results, however, are grouped by zolpidem, escitalopram and placebo arms.

The three posted arms were zolpidem, escitalopram and placebo. The design is described as randomized and triple-masked, but the identities of the masked parties and the procedures used to maintain masking are not reported in the registry record. The allocation ratio, method for generating the random sequence, concealment procedures and any stratification factors are also not reported in the registry record. The arm descriptions give some dosing information, but are truncated and do not establish all details of treatment administration or adjustment.

The primary outcome counts are smaller than the overall enrollment, and the outcome description clarifies that only participants with a calculable total score contribute to the outcome summaries. It also states that protocol noncompleters could be included. The criteria for inclusion in each posted analysis, reasons for missing scores, and handling of missing data beyond this description are not reported in the registry record. The actual analysis population therefore cannot be characterized more fully from the posted information.

One secondary outcome is posted: change in second-night polysomnography sleep efficiency. Although the registry lists three outcome measures, only one secondary result is posted. The registry record does not report a formal statistical analysis plan, the trial’s original sample-size assumptions, a protocol-level definition of the primary comparison strategy or whether interim analyses took place.

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: Subjects who did not meet DSM-IV criteria for primary insomnia, had apnea or periodic limb movement disorder, or had an exclusionary psychiatric diagnosis (generalized anxiety disorder, major depressive disorder, substance abuse) were excluded.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Number of subjects who had total PSQI scores after at least 5 weeks of treatment. The PSQI requires that all questions be answered for a total score to be calculated. This analysis includes participants who did not complete the protocol and also omits those who has missing total scores due to missing items on the PSQI

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Change in Pittsburgh Sleep Quality Index, measured over post treatment minus baseline assessment battery. This averaged 100 days..

The primary endpoint is change in the Pittsburgh Sleep Quality Index total score, calculated as the post-treatment score minus the baseline score. The registry describes this as a self-report measure of sleep quality developed at the University of Pittsburgh. It gives a possible total-score range from 0 to 21, with lower scores described as better sleep. Because the endpoint is a difference, a negative value indicates that the participant’s score decreased after treatment; the registry interprets a negative change as improved sleep quality.

A change score puts each participant’s post-treatment result in relation to their own baseline result. Group means then describe the average change among participants with usable totals. Comparing those means with the placebo mean estimates the difference in average change between each active-treatment arm and the comparator. A difference near zero indicates similar average changes in the posted summaries; the uncertainty around that estimate matters when judging how well the data distinguish among possible effects.

The registry says the primary post-treatment score was collected after at least 5 weeks of treatment and that the interval averaged 100 days. The endpoint is based on a total score, and the registry states that all questionnaire items had to be answered to calculate it. Consequently, participants with missing items that prevented a total score were omitted from the reported primary outcome population. The instrument’s score range and its intended interpretation are described, but no threshold for a clinically important change is reported in the registry record. The endpoint therefore describes reported sleep quality, not an objective laboratory measure.

7. Results Posted in the Registry

• Experimental: Zolpidem: mean -0.86 versus -3.32 on control; difference 2.46 (95% CI 0.20 to 4.72), standardized effect d = 0.66; z-test p = 0.033.
• Experimental: Excitalopram: mean -3.15 versus -3.32 on control; difference 0.17 (95% CI -2.14 to 2.48), standardized effect d = 0.05; z-test p = 0.885.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Change in PSG Sleep Efficiency for the Second Night in the Sleep Lab at Each Timepoint

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Zolpidem: mean 0.43 versus 0.32 on control; difference 0.11 (95% CI -5.46 to 5.68), standardized effect d = 0.01; z-test p = 0.969.
  • Escitalpram: mean 1.16 versus 0.32 on control; difference 0.84 (95% CI -6.65 to 8.33), standardized effect d = 0.07; z-test p = 0.826.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Zolpidem and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Escitalpram and the control. The interval gives the range of effects that remain compatible with the data.

The registry posts one secondary outcome: change in polysomnography sleep efficiency for the second night in the sleep laboratory. The group means are close to one another, and both active-versus-placebo confidence intervals include zero. The unadjusted comparisons therefore do not provide precise evidence of a clear average difference in this secondary measure. The outcome counts and variability differ from those for the primary self-reported measure, so the secondary findings also have their own uncertainty.

The secondary measure is related to the primary question because both assess sleep, but they capture different aspects of it. PSQI is a self-report measure of sleep quality, whereas sleep efficiency is a laboratory sleep-study measure. A similar pattern across these distinct measures could provide context, but a difference between them would not necessarily be contradictory: subjective reports and laboratory measurements are not interchangeable endpoints. The registry does not report a model that combines them or a formal analysis of their relationship.

Only one secondary result is posted, although the registry lists three outcome measures. The other outcome details and results are not reported in the registry record. This limits the ability to assess the full set of outcomes that may have been measured or planned. Secondary outcomes are generally interpreted more cautiously when their status in a prespecified testing hierarchy is unknown and when no multiplicity adjustment is reported. Unadjusted tests do not account for the chance of false-positive findings across multiple comparisons.

The secondary results should be read as supportive descriptive information, not as independent confirmation of the primary result. They neither establish that the primary pattern is present in every measure of sleep nor explain why the primary scores changed. The record does not report whether the secondary analysis was prespecified, whether it was exploratory, or how missing laboratory measurements were handled. Those unreported details reduce the weight that can be placed on the secondary comparisons.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Change in PSG Sleep Efficiency for the Second Night in the Sleep Lab at Each Timepoint

9. Statistical Interpretation

10. Statistical Methods Explained

The posted continuous outcomes are summarized with a mean and standard deviation in each arm. A mean is the arithmetic average of the observed values in that group. The standard deviation describes how spread out individual values are around that group average. It is not the same as the uncertainty in the estimated mean: uncertainty also depends on how many observations contribute. In these results, the group counts differ by outcome, so the precision of a mean can differ across groups even when the means are similar.

What does a mean difference represent?

For each primary comparison, the registry results contrast the active-treatment group mean change with the placebo group mean change. The direction depends on the order used for the subtraction. In the posted primary results, the reported estimate is the active-arm mean minus the placebo mean. Since lower PSQI scores indicate better sleep and negative changes indicate a decrease from baseline, a positive difference means the active-arm average change was less negative, or more positive, than the placebo average change. This direction is a property of the endpoint and subtraction; it is not by itself a judgment about clinical importance.

A mean difference summarizes the separation between group averages. It does not show the full distribution of individual outcomes. Two groups can have different averages while their individual values overlap considerably. The standard deviations in the primary arms are 4.51, 4.52 and 2.63, respectively. The result should therefore be understood alongside both the group counts and the uncertainty interval, rather than from the means alone.

How should the p-value be understood?

A p-value describes how compatible the observed estimate is with a specified null hypothesis under the assumptions of the statistical comparison. A small p-value is not the probability that the null hypothesis is true, nor does it measure the size or importance of an effect. The posted primary p-values are unadjusted: 0.033 for zolpidem versus placebo and 0.885 for escitalopram versus placebo. Because the registry does not report a multiplicity adjustment, these values do not account for the fact that more than one comparison or outcome may be considered.

The registry does not report the trial’s own complete statistical analysis plan, including the exact inferential procedure used by the sponsor. The comparisons available from the arm summaries are simple, unadjusted recalculations. They should not be mistaken for a fully specified, adjusted clinical-trial analysis. If the sponsor’s own analysis conflicted with a recalculation, the sponsor’s analysis would take precedence; the posted record does not flag such a discrepancy.

Why do confidence intervals matter?

A confidence interval expresses uncertainty around an estimate under the assumptions of the method used. A narrow interval would indicate greater precision, while a wide interval would leave more plausible values compatible with the data. For the zolpidem comparison, the reported interval is entirely positive; for the escitalopram comparison, it spans negative and positive values. The intervals convey more about the range of estimates compatible with the data than a p-value alone. They do not resolve questions about bias, missing data, clinical importance or whether the analysis was prespecified.

What are the assumptions behind simple comparisons?

The mean-difference recalculations use the posted group means, standard deviations and counts. They are unadjusted: they do not account for covariates, repeated measurements or other design features beyond the posted summaries. The registry does not report whether the sponsor used a different model, how the original analysis addressed baseline values, or what assumptions were checked. These limitations matter because a summary-statistic comparison cannot reproduce every feature of a trial’s planned analysis.

For continuous outcomes, a normal approximation can be used in some statistical procedures. Such approximations concern the sampling distribution of an estimate, not whether each participant’s raw outcome must be exactly normally distributed. The registry record does not report diagnostic checks or alternative analyses. It also does not report whether a robust or nonparametric method was considered. Results based on summary means and standard deviations thus remain dependent on the assumptions of the simple comparison.

Over-dispersion is a concern in settings where observed variability exceeds what a statistical model expects. In general, underestimating variability can make uncertainty appear smaller than it is, while accounting for extra variability can widen intervals and alter tests. The posted continuous summaries show standard deviations, but the registry does not report a specific over-dispersion assessment. This concept should not be taken as evidence that over-dispersion occurred in this trial.

What do the outcome counts mean?

The primary outcome population is defined by having a total PSQI score after at least 5 weeks of treatment. The registry states that participants who did not complete the protocol could still be included, while missing total scores were omitted. This is not the same as a complete intention-to-treat analysis of every randomized participant. The record does not give a full participant flow, reasons for missing totals, or a method for imputing missing values. These omissions make it difficult to judge whether the analyzed participants differ systematically from those without a usable score.

For the secondary sleep-efficiency outcome, the counts and standard deviations differ from the primary outcome. This reflects that the posted outcome summaries are based on their own available observations; the precise reasons for the different counts are not reported. The same broad statistical ideas apply: the mean estimates average change, the standard deviation describes observed spread, the mean difference contrasts groups, and the confidence interval describes uncertainty. Interpretation should remain tied to the available participants and the analysis details the registry actually records.

11. Confidence Intervals and Precision

Precision concerns how tightly the data estimate a group difference. The primary zolpidem-versus-placebo estimate is 2.46, with a confidence interval from 0.197 to 4.723. The interval is entirely above zero, so the posted unadjusted estimate is compatible with a positive difference across its reported range. The interval is also broad enough to include a range of possible difference magnitudes. The reported estimate should not be treated as exact or as a direct measure of clinical importance.

For escitalopram versus placebo, the estimated difference is 0.17, with a confidence interval from -2.137 to 2.477. This interval crosses zero and includes differences in either direction. Thus, the observed estimate near zero is not especially precise evidence that the underlying average difference is also near zero. The interval leaves uncertainty about both direction and magnitude.

Confidence intervals reflect sampling uncertainty under the analysis assumptions. They do not account automatically for missing outcomes, bias in measurement, deviations from the registered design, or selective reporting. The registry does not state the confidence level, the sponsor’s full analysis method or a clinically important difference threshold. The intervals are therefore useful for describing statistical precision, but they cannot by themselves establish how important the results are or whether the assumptions are appropriate.

The primary group standard deviations are 4.51 for zolpidem, 4.52 for escitalopram and 2.63 for placebo. The primary outcome counts are 21, 20 and 19, respectively. Variation among individual scores and the limited outcome counts contribute to uncertainty in estimating group differences. The posted interval is more informative than relying only on whether an unadjusted p-value falls on one side of a conventional threshold.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size display is a planning illustration based on the observed effect, not on the trial’s original design assumptions. For continuous outcomes, the figures are participants per arm, not a total across the two arms. The stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms and a normal approximation. The target effect is set to the stated fraction of the observed effect. The registry’s original sample-size justification and design assumptions are not reported in the registry record.

The 80% power column gives the number of participants per arm estimated to provide an 80% chance of detecting the specified effect under those planning assumptions, if that effect is the true effect and the assumptions hold. The 90% power column applies the same idea to a higher chance of detection. These are planning quantities, not guarantees: actual power and precision depend on the true effect, variability, study conduct and analysis choices.

Rows planning for 100%, 75% and 50% of the observed effect illustrate how the proposed target effect changes the required sample size. Smaller target effects require more participants because they are harder to distinguish from random variation. The curve should be read as a visual counterpart to those assumptions, rather than as evidence about the trial’s actual power. This is not observed power.

For time-to-event outcomes, the stated convention would be total events, but the posted outcomes are continuous, so the figures are participants per arm. Large planning figures can arise when an observed difference is very small relative to the variability; they should be interpreted as a consequence of the illustration’s inputs, not as a claim about what the original investigators planned.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 2.460; pooled standard deviation σ = 3.739.
2. n = 2 × (1.96 + 0.842)² × 3.739² / 2.460² = 36.3, rounded up to 37 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 2.46                      # observed difference in means
sigma <- 3.73921677698193                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(177216)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 37 (80% power), 49 (90% power)
 75% of observed effect: n per arm = 65 (80% power), 87 (90% power)
 50% of observed effect: n per arm = 146 (80% power), 195 (90% power)
power.t.test: 37.3 
Simulated power at n = 37 per arm: 0.799 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry posts comparisons of two active-treatment arms with placebo for the primary outcome and also posts a secondary outcome with two active-versus-placebo comparisons. It does not report a multiplicity adjustment, a hierarchy for testing outcomes, or a prespecified rule for interpreting several comparisons together. The primary p-value of 0.033 is therefore an unadjusted result. Without a reported testing strategy, it should not be treated as though it controls the overall false-positive risk across all comparisons and outcomes.

The record does not report whether additional outcomes were planned, whether there were interim analyses, or whether the listed outcomes represent the complete set considered by the investigators. Although three outcome measures are listed, only one secondary result is posted. The status and results of the other measures are not reported in the registry record. This limits assessment of selective outcome reporting and the total number of statistical tests that may have informed interpretation.

Missing data also affect interpretation. The primary outcome description requires all PSQI questions to be answered for a total score. It states that people without total scores due to missing information were omitted, while protocol noncompleters could be included if they had a score after at least 5 weeks of treatment. This means the analysis was not necessarily based on every randomized participant. The registry does not report the amount or reasons for missing primary scores, whether missingness differed by arm, or whether sensitivity analyses were performed.

The record does not describe an intention-to-treat analysis, a per-protocol analysis, an imputation method, or a model for incomplete repeated measurements. It also does not identify a full analysis population for each outcome beyond the available descriptions. These are important distinctions: estimates among participants with observed scores can be influenced if availability of those scores is related to treatment or outcome. The extent and direction of any such influence cannot be determined from the registry record.

Finally, the statistical analysis plan, original sample-size rationale, handling of protocol deviations and possible interim monitoring are not reported in the registry record. Their absence does not establish that these procedures were not used; it means their use cannot be verified from the posted information. Interpretation should therefore distinguish the available unadjusted results from a complete account of the trial’s planned analyses.

15. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: inpatient hospitalization (5.0%).

The registry lists serious adverse events for 26 participants at risk in the zolpidem group, 23 in the escitalopram group and 20 in the placebo group. Serious adverse events were recorded for 0, 0 and 1 participants, respectively. The listed top serious-event term is Inpatient Hospitalization, with a reported value of 5.0%. The registry does not provide a narrative account of the event or additional detail about its timing, cause or outcome.

Other adverse events were recorded for 0 participants at risk in the zolpidem group, 2 in the escitalopram group and 0 in the placebo group. These are listed separately from serious adverse events and should not be combined with the serious-event counts. The registry does not report deaths in the posted figures, so death counts are not reported in the registry record.

These numbers are descriptive counts within the reported at-risk groups. They do not establish that an event was caused by a treatment, and the small group counts limit comparisons. The record does not give enough detail to assess event definitions, collection procedures, severity beyond the serious-event classification, or the completeness of safety follow-up. The figures should be read as the adverse-event information recorded in the registry, not as a comprehensive safety evaluation.

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

The posted results describe average changes in a self-reported sleep-quality score among participants with usable total scores. All three arm means were negative, which the registry defines as a decrease in score from baseline. The active-versus-placebo estimates differ: the zolpidem comparison is positive, while the escitalopram comparison is close to zero. The uncertainty intervals show that the estimates have different levels of precision and that the escitalopram comparison is compatible with differences in either direction.

These findings do not establish whether a treatment works or does not work. A group mean is not an individual prediction, and the observed average change does not say how many participants improved, stayed the same or worsened. The registry does not report a threshold for a clinically important change, so statistical estimates cannot be translated into clinical importance from the posted information alone.

The study’s listed enrollment was 69, but the primary outcome summaries use smaller arm counts because the outcome requires a complete questionnaire total. The registry says protocol noncompleters could be included if they had an eligible post-treatment score. Missing totals, the characteristics of people without scores and the full analysis population are not described. This limits how confidently the posted results can be generalized to everyone randomized or to other groups.

The primary outcome is self-reported, while the posted secondary outcome is based on laboratory sleep efficiency. These measures capture different aspects of sleep, and neither should be treated as a substitute for the other. The secondary results do not establish a consistent treatment effect across all aspects of sleep, and the unreported analysis plan and multiplicity handling further limit broad conclusions.

Overall, the posted data show estimates of average score change and their statistical uncertainty. They do not establish causality beyond what can be supported by the full trial methods, prove clinical relevance, resolve missing-data concerns, or provide a complete account of all planned outcomes and analyses.

17. Why This Trial Matters Statistically

This trial illustrates why treatment comparisons require more than looking at whether each group’s average changed. The placebo group also had a negative mean change, so the relevant question is how each active-treatment group’s change compares with the comparator’s change. A within-group decrease alone cannot identify the effect attributable to treatment. The posted mean differences make that between-group contrast explicit.

It also demonstrates the value of considering interval estimates alongside p-values. The zolpidem comparison has an interval entirely above zero, whereas the escitalopram interval spans zero and a range of differences in either direction. These patterns convey information about uncertainty that a single significance label would not. Neither interval, however, answers whether the difference is clinically important, because the registry does not report a meaningful-change threshold.

Outcome availability is another central statistical issue. The primary score requires complete questionnaire responses, and participants without a total score were omitted. The registry indicates that protocol noncompleters could still contribute if they had an eligible score, which is different from restricting analysis to protocol completers. Yet the record does not give a complete account of missingness or the analysis population. That makes participant flow and missing-data assumptions important to interpreting the result.

Finally, the sample-size display is a planning illustration based on observed effects, not a reconstruction of the investigators’ original design. It shows how assumptions about the target effect influence planning requirements, but it cannot substitute for a reported sample-size justification. The missing statistical plan and multiplicity strategy also show why registry summaries should be read as one part of the evidence record, rather than as a complete analysis report.

18. 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 registry summary leaves important design details unavailable. It identifies the trial as randomized, triple-masked and parallel-group, but does not report the random-sequence method, allocation concealment, allocation ratio or which parties were masked. The treatment descriptions are incomplete, so dosing and adjustment procedures cannot be reconstructed in full. The record also does not report eligibility criteria in enough detail to assess how closely the analyzed participants represent the broader population described in the study summary.

For the primary endpoint, the outcome counts are 21, 20 and 19 across the posted arms, while overall enrollment is 69. The registry explains that complete PSQI totals were needed and that participants without such totals were omitted, but it does not report the number or reasons for missing scores by arm. Nor does it describe whether sensitivity analyses tested the effect of missing data. The posted estimates may therefore reflect a subset of participants whose relationship to the full randomized groups is not fully characterized.

The registry does not report the full sponsor analysis, the original sample-size rationale, interim analyses, a multiplicity procedure or a statistical analysis plan. The available mean differences and p-values are unadjusted recalculations from summary statistics. No discrepancy is flagged, but these comparisons cannot capture adjustments or methods that might have been part of a full analysis. Only one secondary result is posted despite three outcome measures being listed.

The primary endpoint is self-reported and no clinically important change threshold is given. The secondary laboratory measure is distinct, and the registry does not provide enough information to combine the two or explain differences between them. Safety reporting is also limited to counts and a top serious-event term, without detailed narratives or death counts. These limitations constrain interpretation of precision, generalizability, safety and the completeness of the evidence; they do not by themselves show that the trial was conducted improperly.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Characteristics of Sleep Patterns in Young Adults With and Without Insomnia — NCT00177216.
• Registry record last updated 2016-03-30; status last verified 2016-02.
• Results first posted 2016-03-30.
• 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.

22. Record Summary

NCT00177216 is listed as a completed, randomized, triple-masked, parallel-group Phase 4 study sponsored by the University of Pittsburgh, with enrollment of 69. The registry describes a study of young adults with and without insomnia and posts primary outcome results for zolpidem, escitalopram and placebo.

The primary endpoint is change in PSQI total score from baseline to post-treatment, with negative values indicating a decrease in score. The posted unadjusted mean differences versus placebo are 2.46 for zolpidem and 0.17 for escitalopram. One secondary laboratory sleep-efficiency outcome is posted. The registry does not report the complete analysis plan, original sample-size assumptions, multiplicity handling or a full account of missing outcomes.