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 Sleep and Teamwork in EMS Study (NCT04456764), a randomized na study. The primary outcome is Fatigue.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04456764 |
| Phase | NA |
| Condition | Fatigue, Sleep |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 708 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Pittsburgh |
| Results posted | Yes |
2. Clinical Question
Population
Emergency Medical Services workers participating in the trial. The primary outcome population is described as participants who provided survey data. The registry record does not report further eligibility details or the number of participants with survey data at each assessment.
Intervention
SaFTiE, a behavioral intervention using real-time text-message assessments of fatigue and sleep during and between scheduled shift work. Tailored alerts were intended to encourage strategies for mitigating fatigue when high fatigue or sleepiness was reported.
Comparator
An attention placebo control, also behavioral. It used real-time assessments of teamwork and alerts about techniques for mitigating poor teamwork. The description also refers to a mobile app delivering goal setting, but the registry record does not provide the full description.
Primary question
The trial assessed fatigue, defined as a response of at least 4 on the Chalder Fatigue Questionnaire, at baseline, 3 months, and 6 months. Its reported comparison is a mixed models analysis; the registry record does not report the effect estimate or confidence interval.
The study addresses fatigue among EMS workers through a workplace-oriented intervention delivered by text message. The registry summary describes a need for fatigue risk management and presents the approach as intended to be scalable and low-cost. Those statements describe the motivation for the trial, not evidence about the primary outcome.
The registered primary measure classified participants according to whether their CFQ response met the stated threshold. The primary outcome timeframe included assessments at baseline and follow-up. The registry record does not explain which assessments or contrasts contributed to the reported mixed models result, so the result cannot be tied to a particular follow-up comparison from the information recorded.
The central statistical question is whether the reported data provide evidence of a difference between the intervention groups in the registered fatigue outcome. The posted p-value is 0.55, but without an effect estimate and confidence interval, the magnitude and precision of the group difference cannot be assessed from the registry record.
3. Trial Design
The trial is titled The Sleep and Teamwork in EMS Study, with the official title Real-time Intervention to Reduce Fatigue Among Emergency Medical Services Workers: A Cluster-randomized Trial. It is registered as randomized, with a parallel model and no masking. The study is cluster-randomized, as noted in the record; the clustering unit and the number of clusters are not reported in the registry record. The listed enrollment is 708.
The two behavioral arms were SaFTiE and an Attention Placebo Control. SaFTiE involved real-time text-message assessments of fatigue and sleep during and between scheduled shifts, followed by tailored alerts when high fatigue or sleepiness was reported. The control used assessments and alerts related to teamwork. Its brief description also mentions a mobile app, but the remaining details are not reported in the registry record.
The study was sponsored by the University of Pittsburgh. The record gives a start date of 2020-09-16 and a primary completion date of 2023-12-11. Its status is terminated. The reason for termination, timing of the decision, and whether termination affected enrollment or follow-up are not reported in the registry record.
The primary outcome was fatigue assessed at baseline, 3 months, and 6 months among participants who provided survey data. The record lists five secondary outcome measures: Pittsburgh Sleep Quality Index (PSQI), Poor Sleep Quality, Inter-Shift Recovery Measure, Acute Fatigue Measure, and Chronic Fatigue Measure. Six outcome measures and six analyses are recorded, but details for the other analyses are not given in the trial details described for this account.
Because allocation was clustered, outcomes within a cluster may be more alike than outcomes across clusters. A statistical analysis that treats every participant as independently randomized could therefore misrepresent the design. The record explicitly excludes a simple individual-level recalculation as misleading and presents the sponsor's own analysis instead. Details of cluster formation, allocation procedures, masking of analysts, and any stratification are not reported in the registry record.
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 | SaFTiE | Attention Placebo Control |
|---|---|---|
| STARTED | 385 | 323 |
| COMPLETED | 319 | 272 |
| NOT COMPLETED | 66 | 51 |
Analysis population for the primary outcome, as defined in the registry: Among participants who provided survey data
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 | SaFTiE | Attention Placebo Control | Total |
|---|---|---|---|---|
| Participants analysed | 385 | 323 | 708 | |
| Age, Continuous | years | 37.7 (SD 10.6) | 35.3 (SD 9.8) | 36.6 (SD 10.3) |
| Sex: Female, Male: Female | Participants | 138 | 105 | 243 |
| Sex: Female, Male: Male | Participants | 232 | 212 | 444 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 24 | 12 | 36 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 339 | 298 | 637 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 5 | 5 | 10 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 1 | 0 | 1 |
| Race (NIH/OMB): Asian | Participants | 5 | 1 | 6 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 8 | 4 | 12 |
| Race (NIH/OMB): White | Participants | 339 | 301 | 640 |
| Race (NIH/OMB): More than one race | Participants | 14 | 8 | 22 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 4 | 4 | 8 |
| Chalder Fatigue Questionnaire (CFQ) | units on a scale | 5.3 (SD 2.9) | 5.2 (SD 3.1) | 5.3 (SD 3.0) |
6. Primary Endpoint
The registry lists the primary outcome as Fatigue, measured over At baseline, 3 months, and 6 months.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is fatigue, recorded as a count of participants meeting a threshold on the Chalder Fatigue Questionnaire (CFQ). A response of at least 4 is classified as mental and physical fatigue; the stated minimum score is 0 and maximum score is 11. The assessment schedule is baseline, 3 months, and 6 months. The population is participants who provided survey data.
Turning a questionnaire score into a threshold-defined outcome creates a readily interpretable classification: whether a participant's response meets the specified criterion. This is a general statistical feature of binary endpoints. It can make group proportions or counts easier to communicate, while discarding information about how far scores lie above or below the threshold. The registry record does not provide the underlying score distributions or the number meeting the threshold at each assessment.
The endpoint is relevant to the trial's stated focus on work-related fatigue. Repeated assessments can describe outcome patterns over time, although the record does not state which time contrast or overall effect was targeted by the reported analysis. The endpoint's threshold and survey-data population also mean the result pertains to the defined measure and recorded respondent population, not automatically to every enrolled participant or to fatigue in every sense.
The registry record reports a mixed models analysis but does not provide the outcome counts, an effect estimate, or a confidence interval. Consequently, the posted result communicates a test statistic through its p-value but does not show the size of the difference or the range of effects compatible with the data.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The primary result is a mixed models analysis with p = 0.55 for the comparison of the two arms. This is the sponsor's reported inferential result in the registry record. It does not, by itself, state the size or direction of the difference in fatigue between groups. No effect estimate or confidence interval is reported, and the registry record does not give the underlying participant counts at the assessments.
In general, a p-value describes how compatible the observed data are with a specified statistical model under a null hypothesis. A value of 0.55 is not an estimate of the probability that the null hypothesis is true, nor does it quantify the probability that the intervention is beneficial or harmful. The registry record does not provide enough detail about the model's contrast or null hypothesis to characterize those elements more specifically.
The result does not establish that the groups had identical outcomes. A non-small p-value can occur when the estimated effect is small, when data are imprecise, or through a combination of factors. Without an effect estimate and confidence interval, readers cannot assess which magnitudes of difference are consistent with the reported data. The record also does not state an equivalence or non-inferiority objective, so the result should not be interpreted as evidence of equivalence.
The analysis is identified as a mixed models analysis. That approach can accommodate structured data such as repeated outcome observations, but the registry record does not describe the model formula, covariance structure, cluster adjustment, estimation method, or handling of missing observations. The trial is cluster-randomized, and the record specifically warns that a simple individual-level re-analysis would be misleading. The sponsor's own analysis therefore takes precedence over a recalculation that ignores the clustering.
The registry lists a survey-data population for the primary outcome. It does not report how many participants contributed data at each timepoint, how missing survey responses were handled, or whether the analysis followed an intention-to-treat principle. Those gaps limit assessment of representativeness and possible bias due to missing data.
The record's terminated status is relevant context, but the reason and consequences of termination are not reported in the registry record. The registry entries do not establish whether the study stopped early relative to its plans or whether the termination affected the analysis. No conclusion about those possibilities should be inferred from status alone.
Overall, the posted result is a non-significant test result from the sponsor's mixed models analysis, not a quantitative estimate of the treatment contrast. The absent estimate and confidence interval prevent a direct assessment of effect magnitude and precision. Interpretation should remain specific to the registered fatigue classification, survey respondents, and analysis as reported.
9. Statistical Methods Explained
The registry reports a mixed models analysis for the primary outcome. In general, mixed models represent both the relationship between predictors and an outcome and sources of dependence among observations. They can be useful when measurements are repeated over time or observations are grouped, because observations from the same person or group may be correlated. The registry record does not report the model specification, so the exact role of repeated measures and clustering in this analysis is not clear.
Why does the cluster-randomized design matter?
In a cluster-randomized trial, groups rather than individual participants are assigned to study arms. Participants within a cluster may share working conditions or other influences, and their outcomes may be correlated. General statistical methods account for this dependence because treating all participants as independent can make uncertainty appear smaller than it is. The record states that a simple individual-level recalculation would be misleading and therefore presents only the sponsor's own analysis. It does not identify the clusters or describe how the analysis accounted for them.
The number of clusters, cluster sizes, and any intracluster correlation estimate are not reported in the registry record. These details matter for understanding how much information the trial contains: a participant count alone does not fully describe the effective information in a cluster-randomized study. No additional calculation of that information is possible from the recorded details.
What does the p-value tell readers?
In general, a p-value measures the compatibility of observed data with a null hypothesis under the assumptions of a statistical test. The reported value is 0.55. It is not the probability that the null hypothesis is true, and it does not measure the size or importance of a difference. The registry record does not report a confidence interval or effect estimate, so the direction, magnitude, and precision of the primary contrast cannot be read from the reported p-value alone.
A confidence interval, as a general statistical concept, gives a range of values compatible with an estimate under a specified method and confidence level. It is useful because it conveys precision and possible effect sizes, not only whether a test crossed a significance threshold. No confidence interval for the primary result is reported in the registry record. The record also does not give the group-specific fatigue counts or proportions needed to describe the observed outcome directly.
How should repeated assessments be understood?
The primary outcome was assessed at baseline, 3 months, and 6 months. Repeated measurements can be analyzed jointly so that the model reflects observations from the same participant over time. In general, this can address the dependence among repeated observations and estimate a specified time or group contrast. The registry record does not state whether the reported result is an overall group effect, a group-by-time effect, a contrast at a particular follow-up, or another model-based test. It also does not report whether baseline outcome was included as an adjustment variable.
The endpoint is threshold-based: participants with a CFQ response of at least 4 meet the recorded fatigue definition. Thresholding a score is a general way to define a binary outcome, but it loses information about variation within each category. The registry record does not describe any complementary analysis of the full CFQ score.
What is unavailable about the analysis?
The record names the method and reports p = 0.55, but does not report model coefficients, standard errors, confidence intervals, covariates, degrees of freedom, or the method used to calculate the p-value. It also does not provide details on assumptions, model diagnostics, software, or treatment of repeated observations and cluster-level dependence. These omissions prevent independent reproduction of the sponsor's analysis.
In general, model assumptions and the choice of analysis population can affect the interpretation of a result. The primary outcome population is described as participants who provided survey data, but the record does not say how missing outcome data were handled or which participants were included at each assessment. The analysis population and its relation to randomized assignment are therefore not fully characterized.
The study details describe planning illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. Such calculations are planning illustrations, not observed power. They do not show the probability that the completed trial detected an effect, and their assumptions do not replace the trial's own design justification. The sample-size justification and planned effect size are not reported in the registry record.
Multiplicity is another general consideration when a study evaluates multiple outcomes or analyses. The record lists six outcome measures and six analyses, but does not report a multiplicity adjustment or a prespecified hierarchy of tests. Without the statistical analysis plan, it is not possible to determine how the primary result relates to any family of planned comparisons.
10. Analyses Reported by the Sponsor
| Method | Estimate | 95% CI | P-value |
|---|---|---|---|
| Mixed Models Analysis | not reported | 0.550 |
The sponsor's reported primary analysis is a mixed models analysis with p = 0.55. No effect estimate, confidence interval, group-specific outcome count, or model detail is reported in the registry record. The posted result should therefore be read as the sponsor's inferential test result, not as a complete quantitative description of the treatment contrast.
A simple recalculation from summary statistics is not presented. The design is cluster-randomized, and the registry record notes that a simple individual-level re-analysis would be misleading. In this setting, a recalculation that treated participants as independently randomized would fail to reflect the design's clustering. The sponsor's own analysis takes precedence.
The record's planning illustrations use an observed effect as a basis for planning calculations under stated assumptions. They are not a second estimate of the trial result, and they are not observed power. The registry record does not report enough detail to reproduce the mixed models analysis or independently verify the sponsor's test. That limitation does not change the posted p-value, but it constrains what can be inferred about the magnitude and precision of the effect.
11. Multiplicity, Missing Data and Analysis Populations
The registry record lists six outcome measures and six analyses. It identifies fatigue as the primary outcome and names five secondary measures: Pittsburgh Sleep Quality Index (PSQI), Poor Sleep Quality, Inter-Shift Recovery Measure, Acute Fatigue Measure, and Chronic Fatigue Measure. It does not report a testing hierarchy, a multiplicity adjustment, or a statistical analysis plan describing how the outcomes and analyses were prioritized.
In general, evaluating multiple outcomes or contrasts can increase the chance of observing at least one nominally unusual result. Adjustments or a prespecified hierarchy are possible approaches to managing that issue, but the registry record does not state whether either was planned or used. The reported primary p-value should be considered in the context of this missing information; no adjustment should be assumed.
The primary outcome population is described as participants who provided survey data. The record does not report the number of respondents at each assessment, the pattern or reasons for missing survey data, or the method used to handle missingness. It also does not say whether participants with incomplete follow-up contributed available observations to the mixed model. These omissions make it difficult to assess whether the analyzed respondents represent all randomized participants.
The registry record does not specify an intention-to-treat, per-protocol, or other named analysis population. It does not explain how changes in participation, protocol adherence, or missing measurements were handled. The study's terminated status adds context, but the reason for termination and any impact on follow-up or analysis are not reported in the registry record.
These are limitations of what can be established from the registry record, not evidence that a particular procedure was or was not used. The statistical analysis plan, missing-data procedures, analysis-population definition, and multiplicity strategy are not reported in the registry record.
12. What the Result Does, and Does Not, Mean
The posted result documents a mixed models analysis of the registered fatigue outcome, with p = 0.55. The endpoint classifies participants by a CFQ response threshold of at least 4 and was assessed at baseline, 3 months, and 6 months. The outcome population is described as participants who provided survey data.
The result does not provide an effect estimate or confidence interval. It therefore does not show whether the observed group difference favored SaFTiE or the Attention Placebo Control, how large that difference was, or how precisely it was estimated. The p-value alone cannot answer those questions. It also does not establish that the groups were identical or that any meaningful difference has been ruled out.
The analysis is specific to the recorded fatigue measure, its threshold, the survey respondents, and the mixed models result reported by the sponsor. It should not be generalized automatically to every aspect of fatigue, to all EMS workers, or to the secondary measures. The listed outcomes concern sleep quality, inter-shift recovery, and acute and chronic fatigue, but the registry entries do not provide their results.
The trial's cluster-randomized design is important to interpretation. Participants assigned within the same cluster may have related outcomes, and a valid analysis needs to account for that structure. The registry record warns against a simple individual-level recalculation and gives the sponsor's analysis instead. Details needed to assess that model are not reported in the registry record.
The record states that the study was terminated, but does not give the reason or explain whether termination affected recruitment, follow-up, or analysis. It would be inappropriate to infer those effects from the status alone. Similarly, the record does not report missing-data handling or an analysis population beyond participants who provided survey data.
Accordingly, the result is best understood as a reported statistical test without enough accompanying estimates to judge the size or precision of the primary contrast. It is not a standalone demonstration of equivalence, and it does not establish a clinical conclusion about the intervention.
13. Why This Trial Matters Statistically
This trial raises a statistical issue that is central to many workplace and health-services studies: randomization may occur at the level of groups rather than individuals. When outcomes within a cluster are correlated, analysis needs to reflect that dependence. The registry record explicitly cautions that a simple individual-level recalculation would be misleading, making the sponsor's own analysis the appropriate result to report from the available information.
The study also illustrates why a p-value is not a complete result. The primary analysis reports p = 0.55, but no effect estimate or confidence interval is reported in the registry record. Readers can identify the reported test result, but cannot judge the magnitude, direction, or precision of the group contrast. Reporting those quantities alongside a test result is generally important for substantive interpretation.
The primary endpoint is a threshold-based classification of a questionnaire response, assessed repeatedly. Thresholds can make outcomes easier to communicate, while reducing the detail carried by the underlying score. Repeated assessment also raises questions about the modeled time contrast and the handling of within-person dependence. The registry record does not describe those details, highlighting the value of a complete statistical analysis plan and transparent model reporting.
Finally, the record identifies survey respondents as the primary outcome population without describing missing responses or the analysis population in further detail. In general, transparent reporting of follow-up, missing data, and multiplicity helps readers understand what evidence a result represents. These reporting gaps do not determine the result, but they limit how fully it can be interpreted.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The primary result is reported without an effect estimate, confidence interval, or group-specific fatigue counts. As a result, the registry record does not allow readers to assess the direction, magnitude, or precision of the difference. The p-value alone cannot indicate whether effects of potential importance are compatible with the data.
The study is cluster-randomized, but the registry record does not identify the clusters, report their number or sizes, or describe the adjustment used for clustering. It gives only the method label, mixed models analysis, and the primary p-value. The analysis cannot be independently reproduced from those details. The record itself notes that a simple individual-level recalculation would be misleading.
The outcome was assessed at baseline, 3 months, and 6 months, but the reported contrast is not specified. The model's covariates, treatment of repeated observations, and handling of baseline measurements are not reported in the registry record. Nor does the record provide the number of participants contributing data at each timepoint or explain missing-data procedures.
The primary endpoint applies a threshold to the CFQ and is limited to participants who provided survey data. The record does not provide the full score distribution or clarify how the respondent population relates to all randomized participants. The listed secondary outcomes are named, but their results are not included among the registry entries used for this account. Multiplicity procedures and a statistical analysis plan are also not reported.
The trial is marked terminated, but the reason, timing, and consequences of termination are not reported in the registry record. It is therefore not possible to assess from this information whether termination affected enrollment, follow-up, or planned analyses. The enrollment listed in the record is 708; arm-specific enrollment and the number of analyzed participants are not reported.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: The Sleep and Teamwork in EMS Study — NCT04456764.
- Registry record last updated 2025-05-18; status last verified 2025-05.
- Results first posted 2024-11-25.
- 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
The Sleep and Teamwork in EMS Study is a cluster-randomized, parallel trial with no masking, comparing the behavioral SaFTiE intervention with an Attention Placebo Control. The listed enrollment is 708, and the sponsor is the University of Pittsburgh. The record gives a start date of 2020-09-16, a primary completion date of 2023-12-11, and a status of terminated.
The primary outcome is fatigue, defined as a CFQ response of at least 4, assessed at baseline, 3 months, and 6 months among participants who provided survey data. The registry reports a mixed models analysis with p = 0.55. An effect estimate and confidence interval are not reported in the registry record, and the record cautions that a simple individual-level recalculation would be misleading because of the cluster-randomized design.
The record lists five secondary outcomes, but their results are not included in the registry record. Details of the cluster structure, missing-data handling, multiplicity strategy, and reason for termination are not reported in the registry record.