Cardio-pulmonary Rehabilitation and Sleep Quality: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Cardio-pulmonary Rehabilitation and Sleep Quality (NCT04668599), a registered phase not stated study. The primary outcome is Improvement in Sleep Quality Using Pittsburgh Sleep Quality Index.

2. Clinical Question

The study asks whether sleep quality changes after cardiopulmonary rehabilitation among people with chronic lung or cardiac disease who are eligible for rehabilitation. Its primary measure is the Pittsburgh Sleep Quality Index (PSQI), assessed before and after rehabilitation. The primary outcome description identifies the population as those who completed pulmonary rehabilitation over 8 weeks on average.

The rationale in the registry focuses on the connection between disturbed sleep and chronic illness, and on uncertainty about whether rehabilitation is associated with changes in sleep quality and how long any such changes might last. The planned primary assessment is at the end of rehabilitation; longer-term follow-up is not described in the primary outcome timeframe. The record also lists change in Insomnia Severity Index as a secondary outcome. It does not report analyses or results for either sleep measure.

3. Trial Design

This is a prospective cohort study, not a randomized controlled comparison. The registry lists cardiopulmonary rehabilitation as the intervention and describes participants with chronic lung or cardiac diseases who are eligible for pulmonary or cardiac rehabilitation. It reports an enrollment of 106 and a status of completed. The study start date is 2020-05-11, and the primary completion date is 2024-10-11.

The primary outcome is a before-and-after assessment of sleep quality using the PSQI, with a timeframe of 8 weeks on average. The stated primary population is those who completed pulmonary rehabilitation. The record describes eligibility for rehabilitation but does not report how many enrolled participants completed the program or contributed data to the primary outcome. The stated enrollment should therefore not be read as the number included in an outcome analysis.

The registry describes the study arm as patients with chronic lung or cardiac diseases. It says that people with obstructive or restrictive lung disease eligible for pulmonary rehabilitation and people with cardiac disease eligible for cardiac rehabilitation may be included. The record also identifies heart failure, coronary artery disease and cardiomyopathies as examples of cardiac disease. It does not report the number of participants in each disease group, or whether outcomes were analyzed separately by diagnosis.

Because there is no like-for-like control comparison, a before-and-after change would describe the observed course among participants assessed around rehabilitation. It would not, on its own, separate a rehabilitation-associated change from other changes over time or from differences in who completed follow-up. The allocation method is not stated. The registry record does not report the protocol, recruitment details, the duration of follow-up beyond the primary timeframe, or a statistical analysis plan.

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.

Baseline to Completion of Rehab

Completion of Rehab to 3-Month Followup

Analysis population for the primary outcome, as defined in the registry: those who completed PR (8 weeks)

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 Improvement in Sleep Quality Using Pittsburgh Sleep Quality Index, measured over 8 weeks on average.

The primary endpoint is improvement in sleep quality measured using the Pittsburgh Sleep Quality Index. The registry describes the outcome as a mean, with standard deviation, in units on a scale. The PSQI is a questionnaire with seven components, each scored from 0 to 3. Its total score ranges from 0 to 21. The record states that a score of less than 5 indicates good overall sleep quality and a score of 5 and more indicates poor overall sleep quality.

The endpoint is framed as a change between measurements taken before and after cardiopulmonary rehabilitation. A change score can describe whether scores tended to move in one direction over that interval, while a mean gives a measure of the average score or change in the group. The standard deviation describes variation among individual scores around the mean; it is not a measure of the precision of the mean. A confidence interval, if reported, would address precision of an estimate, but an interval is not reported in the registry record.

The registry states that a minimal clinically important difference was determined from a literature review to be 3 between before and after measurements. This is a reference for interpreting the size of a change, not a result from this cohort. The record does not report the cohort’s baseline score, follow-up score, mean change, standard deviation, or the number of participants with paired measurements. It therefore does not show whether the observed change reached that stated threshold.

The secondary outcome is change in Insomnia Severity Index. Its measurement details and results are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a continuous outcome summarized as a mean and standard deviation. These are descriptive statistics: the mean gives the average score or average change in the analyzed group, and the standard deviation describes how dispersed individual observations are around that average. A standard deviation is not the same as a standard error or confidence interval. The latter quantities concern uncertainty in an estimate, and neither is reported for the primary outcome in the registry record.

What a before-and-after measure represents

For a participant with both assessments, a before-and-after change is based on the two measurements from that person. A group mean change would summarize those individual changes. This can be useful for describing change over time, but it does not by itself establish that the intervention caused the change. In a nonrandomized cohort, other events during follow-up and differences among participants can also contribute. The registry describes a before-and-after outcome, but does not specify the exact statistical test or model used to analyze it.

Paired data also require both measurements for the same participant. If one assessment is missing, that participant may not contribute to a simple paired change estimate. Other analytic approaches can use incomplete data under stated assumptions, but the record does not say whether such methods were used. The number of participants with complete paired PSQI data and the handling of missing observations are not reported.

How to read a mean and its uncertainty

A point estimate such as a mean change describes the value estimated from the analyzed participants. A confidence interval would show a range of values compatible with the data and the statistical method at the stated confidence level. A narrow interval generally indicates greater precision than a wide interval. An interval’s relation to a meaningful-change threshold can help show whether the data are compatible with changes that are smaller than, near, or larger than that threshold. No confidence interval for the PSQI outcome is reported in the registry record, so that assessment cannot be made for this cohort.

A p-value, if available, would describe how surprising the data would be under a specified statistical model and a null hypothesis. It does not measure the size or clinical importance of a change, and it is not the probability that a hypothesis is true. The registry record does not report a p-value or the test that would have generated one. A statistical analysis plan is not reported, so the intended inferential procedures cannot be reconstructed from the outcome description alone.

Scale interpretation and the stated threshold

The PSQI total score runs from 0 to 21, with higher scores falling on the poor-sleep side of the registry’s stated categories: less than 5 indicates good overall sleep quality, and 5 and more indicates poor overall sleep quality. The record also states that 3 was identified as the minimal clinically important difference between before and after measurements. A threshold of this kind is used as a contextual guide to the size of a change; it does not replace an estimate of the change or its uncertainty. The record does not report how the threshold was applied in an analysis, or whether results were assessed against it.

Analyzing a continuous score preserves information about the amount of change across the scale. Categorizing scores using the good- and poor-sleep cut point answers a different question: how many participants fall on either side of that threshold. The primary outcome is described as a mean and standard deviation, and the registry does not report a categorical analysis of the PSQI. The two forms of analysis should not be treated as interchangeable.

Planning illustrations are not observed results

The registry’s planning assumptions describe an illustration 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. They specify that non-time-to-event illustrations are expressed as participants per arm for the stated power level. These are planning assumptions, not a description of this cohort’s allocation or an observed analysis. The record explicitly notes that the study is not a randomized comparison and that the arms are not a like-for-like control comparison. The planning illustration should therefore not be interpreted as evidence that the study used equal allocation, had two comparable arms, or achieved a particular power. The registry record does not report the study’s own sample-size justification.

Sample-size calculations are planning tools that depend on assumptions about the effect to detect, variability, allocation and analysis. They do not establish the probability that a completed study has found a true effect, and they cannot substitute for the observed estimate and its uncertainty. No observed power should be inferred from a planning illustration. In this record, the outcome analysis and the observed effect used for the illustration are not reported alongside results that would allow readers to evaluate the estimate.

What can and cannot be concluded from the listed methods

The registry identifies a continuous primary measure, its scale, the before-and-after framing, and the target population. It also lists a secondary insomnia measure. Those details describe the intended measurement questions, not the analytic choices actually made. The analysis model, covariates, handling of repeated observations, missing-data method, analysis population and multiplicity approach are not reported in the registry record. Without those details and the estimates themselves, statistical interpretation must remain limited to the design and outcome definitions.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Patients Who Completed Rehab (8 Weeks)", "Patients Who Completed Rehab and 3-month Followup ")
n   <- c(63, 59)
m   <- c(-3.6, -1.6)
sp  <- c(2.7, 2.8)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Patients Who Completed Rehab (8 Weeks)  63  -3.600  2.700  -4.280  -2.920
CARM  Patients Who Completed Rehab and 3-month Followup   59  -1.600  2.800  -2.330  -0.870

11. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures and identifies change in Insomnia Severity Index as a secondary outcome alongside the primary PSQI outcome. It does not report the number of statistical analyses, an analysis plan, or a strategy for handling multiple outcomes or multiple comparisons. When several outcomes or tests are considered, the chance of at least one apparently notable result can increase; a prespecified analysis plan helps readers distinguish the main question from exploratory analyses. The record does not state whether an adjustment or hierarchy was planned, so none should be assumed.

Missing-data handling is also not reported. The primary population is described as those who completed pulmonary rehabilitation, but the record does not give the number who completed the program, the number with baseline and follow-up PSQI measurements, or the reasons for missing measurements or noncompletion. These details matter because the people with complete data may differ from those without complete data. An analysis restricted to completers describes that analyzed group and may not represent all enrolled participants.

The analysis populations are not reported in the registry record. It is therefore unclear whether the planned analysis included all enrolled participants, only rehabilitation completers, or another defined group. The record does not specify how participants with incomplete rehabilitation or incomplete outcome assessments were handled. These omissions limit assessment of possible selection effects and of the reproducibility of any analysis.

12. Safety Results

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

Deaths

Other (non-serious) adverse events

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

The registry lists one group, titled Patient With Chronic Lung or Cardiac Diseases, with 106 participants at risk for serious adverse events and 0 participants affected. It also lists 106 at risk for other adverse events and 0 affected, with 0 deaths. These are the posted counts for the listed group. The record gives no serious adverse-event terms.

A count of zero means that no events of the specified type are recorded for this group in the registry entry. It does not demonstrate that the risk is absent. Interpretation depends on what events were collected, the reporting period, completeness of follow-up and the definitions used. Those details are not reported in the registry record. The counts are not a comparison between randomized treatment and control groups: the study is described as a prospective cohort, and the record cautions that the arms are not a like-for-like control comparison.

The safety figures should therefore be read as descriptive registry reporting, not as a comparative estimate of safety or proof that no adverse events occurred in any broader population. The number of participants contributing outcome data may also differ from the safety count; that relationship is not reported.

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

The registry record establishes that the study was designed to examine sleep quality around cardiopulmonary rehabilitation in people with chronic lung or cardiac disease. It defines the primary outcome as before-and-after change in PSQI, describes the scale and its interpretation, and gives an average timeframe of 8 weeks. It also identifies change in Insomnia Severity Index as a secondary outcome.

Those design details do not tell readers what happened to participants’ sleep scores. The record does not report the observed PSQI change, baseline or follow-up mean, standard deviation, confidence interval, or p-value. It also does not report results for the secondary outcome. As a result, no conclusion about the size, direction or precision of the observed change can be drawn from the registry entry. The stated minimal clinically important difference of 3 is an interpretive reference, not an outcome finding.

Even if a before-and-after change estimate were available, this design would describe change among participants over the observed interval rather than isolate the causal effect of rehabilitation. A control comparison, and a method for addressing differences between groups, are not described. The record also does not report whether the analyzed participants represent all those enrolled or only those who completed rehabilitation and outcome assessments.

The safety counts are similarly limited: they record zero serious adverse events, zero other adverse events and zero deaths in the listed group, but do not constitute a controlled comparison or establish absence of risk. The most defensible reading is therefore that the registry documents a completed cohort study and an intended sleep-quality assessment, while the outcome results needed to judge the observed change are not reported in the registry record.

14. Why This Trial Matters Statistically

This study raises a measurement and design question that is important in clinical research: how to describe a patient-reported outcome before and after a rehabilitation program when the study does not include a randomized, like-for-like control comparison. The prospective cohort design can document the timing and pattern of observations, but interpretation of change depends on the analysis population, follow-up completeness and factors that may change alongside participation. Those details are not reported in the registry record.

The choice of a continuous questionnaire score makes it possible to describe the size and variability of changes rather than only whether participants cross a category threshold. The registry also states a PSQI threshold for good versus poor sleep quality and a minimal clinically important difference of 3. These provide distinct forms of context: one categorizes overall score, while the other is a reference for interpreting change. Neither can replace reporting an estimate with its uncertainty.

Statistically, the record also illustrates the importance of separating a study’s outcome definitions from its results and analysis plan. A completed status does not itself supply an effect estimate, and an outcome description does not reveal how missing assessments or multiple outcomes were handled. Without these details, readers cannot assess precision, potential selection effects, or how the primary question was tested.

The enrollment of 106 and the listed safety counts describe the registry entry, but do not establish how many participants contributed to the primary analysis or whether observed changes can be attributed to rehabilitation. The registry’s planning assumptions are not the trial’s own design justification and should not be taken as evidence of achieved power. The central statistical contribution available from this record is therefore the framing of a clinically relevant measurement question, together with a clear need for outcome estimates and analysis details to support interpretation.

15. 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 most consequential limitation for interpreting this registry entry is that primary and secondary outcome results are not reported. There is no PSQI change estimate, associated variability or uncertainty, and no reported result for the Insomnia Severity Index. The record therefore does not allow assessment of the magnitude or precision of change, or comparison with the stated minimal clinically important difference of 3.

The study is described as a prospective cohort rather than a randomized comparison. The registry cautions that the arms are not a like-for-like control comparison, and allocation is not stated. Accordingly, a before-and-after difference, if reported elsewhere, would not by itself establish that rehabilitation caused the change. The record does not describe an approach to account for time trends, co-occurring changes or differences between participants.

The outcome population is described as rehabilitation completers, but the number who completed rehabilitation and the number with paired PSQI assessments are not reported. The record also does not explain missing data, reasons for noncompletion, participant characteristics by outcome availability, or the analysis populations. These omissions make it difficult to judge whether the analyzed group could differ systematically from the enrolled cohort.

The registry does not report the statistical analysis plan, the model or test used, adjustment for covariates, handling of multiple outcomes, or whether outcome analyses were prespecified. The study includes people with different lung and cardiac conditions, but the number in each group and any condition-specific results are not reported. The primary timeframe is 8 weeks on average; longer-term outcome results are not described. These limitations are specific to the available registry information and restrict interpretation of both efficacy-related outcomes and safety reporting.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Cardio-pulmonary Rehabilitation and Sleep Quality — NCT04668599.
• Registry record last updated 2024-11-05; status last verified 2024-11.
• Results first posted 2024-11-05.
• 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.

19. Record Summary

NCT04668599, titled Cardio-pulmonary Rehabilitation and Sleep Quality, is listed as a completed prospective cohort study sponsored by MetroHealth Medical Center. The registry reports enrollment of 106, a study start date of 2020-05-11 and a primary completion date of 2024-10-11.

The study concerns cardiopulmonary rehabilitation for people with chronic lung or cardiac disease. Its primary outcome is before-and-after change in Pittsburgh Sleep Quality Index, described as a mean and standard deviation, with an 8 weeks on average timeframe. The record identifies change in Insomnia Severity Index as a secondary outcome.

The registry record does not report outcome analyses or results. It lists 0 serious adverse events, 0 other adverse events and 0 deaths among 106 at risk in the described group. These counts are descriptive and do not constitute a controlled comparison.