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 Heart at Work Study (NCT04075279), a registered phase not stated study. The primary outcome is 24-hour Heart Rate.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04075279 |
| Phase | Phase not stated |
| Condition | Occupational Diseases, Cardiovascular Diseases, Cardiovascular Risk Factor |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 19 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Pittsburgh |
| Results posted | Yes |
2. Clinical Question
Population
The study concerns people in occupations with high physical activity, in the context of the cardiovascular health effects associated with occupational activity. The registry record reports enrollment of 19 participants. Specific eligibility criteria, participant characteristics, and the occupations represented are not reported in the registry record.
Intervention
There is no assigned intervention described. This is an observational study intended to examine cardiovascular mechanisms in people with high activity occupations. The record describes a one-week monitoring period involving physical activity and cardiovascular measures, but details of recruitment, monitoring procedures, and adherence are not reported in the registry record.
Comparator
No randomized or like-for-like control comparison is described. The registry record says that allocation was not stated and cautions that the arms are not a like-for-like control comparison. The identities and characteristics of any arms or comparison groups are not reported in the registry record.
Primary question
The primary outcome is 24-hour heart rate, measured in beats per minute. The stated aim is to calculate average heart rate over each 24-hour period throughout a one-week monitoring period. The broader study aim is to examine cardiovascular mechanisms related to increased cardiovascular mortality in people with high activity occupations. The registry record does not report a numerical estimate, a comparison result, or an analysis for the primary outcome.
Statistically, the record describes measurement rather than a randomized treatment-effect question. Without a defined comparison and reported outcome estimates, it cannot establish whether differences in occupational activity are associated with differences in heart rate, or quantify the size or precision of any such relationship. The available record identifies the scientific focus and outcome, but does not give enough information to evaluate an observed association.
3. Trial Design
The Heart at Work Study is registered as an observational study, not as a randomized intervention trial. Its stated purpose is to examine cardiovascular mechanisms related to increased cardiovascular mortality among people with high activity occupations. The University of Pittsburgh is listed as sponsor. The record marks the study as completed, with a start date of 2019-10-17 and primary completion date of 2020-04-20. Enrollment is listed as 19.
The primary measurement is 24-hour heart rate in beats per minute. The outcome description says that average heart rate is to be calculated over each 24-hour period throughout a one-week monitoring period. The record also lists secondary outcomes covering 24-hour ambulatory systolic blood pressure, nocturnal heart rate variability measures, and physical activity measures. These include steps per day, moderate-to-vigorous physical activity, and light physical activity. The record lists 12 outcome measures, but does not provide full measurement procedures or numerical results for them.
The record does not describe a randomized allocation. It notes that allocation was not stated and that any arms are not a like-for-like control comparison. The identities, sizes, and composition of any groups are not reported in the registry record. Nor are recruitment methods, eligibility criteria, or the characteristics of the enrolled participants reported in the registry record.
Although the study status is completed, the registry record lists zero analyses. That does not establish whether analyses were performed outside the registry; it means that no analysis is represented in the record. Numerical outcome estimates, uncertainty intervals, and statistical tests are not reported in the registry record. Sample-size justification, monitoring procedures beyond the stated one-week period, and the detailed statistical analysis plan are also not reported in the registry record. Consequently, the design and aims can be described, but the evidence for the primary question cannot be assessed from the registered results alone.
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 | Middle-aged Males in High Activity Occupations |
|---|---|
| STARTED | 19 |
| COMPLETED | 19 |
| NOT COMPLETED | 0 |
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | Research Study Participation |
|---|---|---|
| Participants analysed | 19 | |
| Age, Continuous | years | 46.6 (SD 7.9) |
| Sex: Female, Male: Female | Participants | 0 |
| Sex: Female, Male: Male | Participants | 19 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 4 |
| Race (NIH/OMB): White | Participants | 13 |
| Race (NIH/OMB): More than one race | Participants | 2 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Region of Enrollment: United States | participants | 19 |
| Occupational Industry: Food Service | Participants | 8 |
| Occupational Industry: Material Moving | Participants | 9 |
| Occupational Industry: Healthcare | Participants | 1 |
| Occupational Industry: Building and Grounds Maintenance | Participants | 1 |
6. Primary Endpoint
The registry lists the primary outcome as 24-hour Heart Rate, measured over 24 hours.
| Element | Registry entry |
|---|---|
| Result type | Least Squares Mean |
| Measure of spread | Standard Error |
| Unit | beats per minute |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is 24-hour heart rate, expressed in beats per minute. The record describes calculating average heart rate over each 24-hour period throughout a one-week monitoring period. This endpoint is a continuous measure: it can take values across a scale rather than being limited to a set of categories. The registry specifies a least-squares mean as the summary measure and standard error as the dispersion measure.
In general, heart rate summarizes cardiac rhythm frequency over the measurement period. Repeated monitoring over a full daily cycle can describe heart rate across ordinary activity and rest periods, rather than at a single measurement time. That is a general rationale for a 24-hour measure; the registry record does not give further details about the measurement device, data processing, or the specific rationale for selecting this endpoint.
A least-squares mean is generally a model-based estimate of a mean. Depending on the model, it may account for covariates or other features of the data. The registry record does not report the model, adjustment variables, or estimation method beyond naming the least-squares mean. A standard error describes the estimated uncertainty of a mean, rather than the spread of individual participants’ measurements. No numerical least-squares mean or standard error is reported in the registry record, so the endpoint’s observed level and precision cannot be assessed.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies 24-hour heart rate as the primary outcome and gives its measurement unit, summary type, dispersion type, and monitoring timeframe. It does not report the numerical heart-rate estimate, its standard error, a confidence interval, or a statistical test. It therefore does not provide an observed primary result to interpret. The record also lists zero analyses, which means no analyses are represented in the registry record; it does not show whether analyses were performed elsewhere.
The study’s observational purpose matters when interpreting its question. It seeks to examine cardiovascular mechanisms in the context of high activity occupations, rather than assigning participants to a treatment. The registry cautions that allocation was not stated and that arms are not a like-for-like control comparison. Without a clearly described comparison, participant characteristics, and outcome estimates, a reader cannot determine the direction or magnitude of any association between occupational activity and heart rate from this record.
In general, an estimate is more informative when accompanied by a measure of uncertainty. A standard error describes uncertainty around an estimated mean; a confidence interval, if reported, would give a range of values compatible with the data and analysis under its assumptions. Neither the numerical standard error nor a confidence interval for the primary outcome is reported in the registry record. The named dispersion measure alone does not indicate how precisely the endpoint was estimated.
The record lists secondary outcomes involving blood pressure, heart rate variability, and physical activity patterns. Their names establish the domains of interest, but do not establish what values were observed or whether any differences or associations were present. No secondary outcome estimates or statistical tests are reported in the registry record. The record’s total of 12 outcome measures does not supply the missing estimates or clarify which outcomes were analyzed.
The safety entry reports zero serious adverse events, zero other adverse events, and zero deaths in the group titled “Research Study Participation,” with 19 at risk. These registry counts should be read as recorded safety figures, not as evidence about cardiovascular outcomes or comparative safety. The record does not provide further details about event ascertainment or follow-up. Overall, the posted record describes the study’s aims and selected design features but does not provide the results needed to judge the primary outcome’s value, precision, or relationship to occupational activity.
9. Statistical Methods Explained
What does a continuous outcome mean?
The primary outcome, 24-hour heart rate, is identified as continuous and measured in beats per minute. In general, a continuous outcome can vary along a measurement scale, so analysis often focuses on estimating its mean or another summary rather than counting participants in categories. The registry names a least-squares mean, but does not report the numerical estimate or model details. The meaning of a model-based mean depends on how the model was specified and which observations or covariates were included.
What is a least-squares mean?
In general, a least-squares mean is an estimated mean derived from a statistical model. It may be adjusted for variables included in that model, which can make it differ from a simple arithmetic average. The registry record does not report whether adjustment variables were used, what model was fitted, how repeated measurements were handled, or whether the estimate represents a participant-level summary or another analytic quantity. The outcome description refers to averages over daily periods across a one-week monitoring period, but does not explain how those repeated measurements were incorporated into the stated least-squares mean.
What does the standard error describe?
In general, a standard error describes the uncertainty of an estimated quantity, such as a mean. It is not the same as the standard deviation, which describes variation among observations. A smaller standard error generally corresponds to a more precise estimate under the analysis assumptions, while a larger one indicates greater uncertainty. The registry names standard error as the dispersion measure but does not report its value. Without that value, a reader cannot judge the reported precision or use the endpoint summary to assess a confidence interval.
Why do the comparison details matter?
Statistical comparisons require a clear definition of the groups, exposure, or conditions being compared. This is an observational study, and the registry says allocation was not stated and any arms are not a like-for-like control comparison. The identities and characteristics of the arms are not reported in the registry record. As a general principle, differences between groups in an observational study may reflect characteristics other than the exposure of interest. Adjusted analyses can sometimes address measured differences, but they cannot automatically resolve unmeasured or poorly measured differences. The record does not report a comparison model or adjustment strategy.
How should planning calculations be understood?
In general, a sample-size calculation is a planning exercise: it describes how much information a future study might need under assumptions about the effect, variability, significance level, allocation, and analysis. It is not a measure of the probability that a completed study has detected a real effect. The registry’s planning assumptions describe a normal approximation, two-sided significance level of 0.05, equal allocation between two arms, and effects defined as fractions of an observed effect. These are planning assumptions, not evidence that the study was randomized or that the stated comparison is appropriate. No numerical planning estimates or underlying observed effect are reported in the registry record. Any such planning illustration must not be interpreted as observed power or as a result of the study.
What can be concluded from the analysis listing?
The registry lists zero analyses. This is a statement about what the registry record contains, not proof that investigators did not analyze the measurements. The record does not report a test statistic, p-value, confidence interval, effect estimate, model specification, or analytic population for the primary outcome. General statistical methods cannot fill in those absent results. They can clarify what types of information would be needed to assess an estimate, but cannot establish what the study found.
Why can repeated measures require care?
As a general matter, measurements taken repeatedly from the same participant are related rather than independent observations. An analysis that treats related measurements as independent can misstate uncertainty. Appropriate methods depend on the timing and structure of measurements, the research question, and the model assumptions. The registry describes average heart rate over each 24-hour period throughout a one-week monitoring period, but does not report the data structure or the method used to account for repeated observations. No particular repeated-measures method can therefore be attributed to this study.
What is over-dispersion in general?
Over-dispersion occurs when observed variability is greater than a statistical model expects. It is especially relevant to some count-data models, where underestimated variability can make uncertainty appear too small. The primary endpoint is a continuous heart-rate measure, so the record does not establish that a count model or an over-dispersion correction was used. In general, checking whether a model’s variability assumptions fit the data is important, but the registry does not report diagnostic checks or variance assumptions.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 12 outcome measures, including the primary heart-rate outcome and secondary measures of blood pressure, heart rate variability, and physical activity. When several outcomes are tested, the chance of at least one apparently notable result can increase if each is assessed separately without accounting for multiplicity. That is a general statistical concern, not a finding about this study. The registry record does not report a multiplicity adjustment, a hierarchy of secondary analyses, or which outcomes were analyzed. It also lists zero analyses, so no set of analysis results is available for evaluating how multiple outcomes were handled.
Missing-data methods are not reported in the registry record. The record does not describe whether monitoring could be incomplete, how missing measurements were identified, how missingness was handled, or whether any sensitivity analyses were planned or performed. This matters generally because estimates based on incomplete measurements can depend on why measurements are missing and on the method used to address them. No missing-data assumptions can be attributed to this study from the recorded information.
The analysis populations are also not reported in the registry record. It does not state which participants contributed to the primary or secondary outcome analyses, whether all enrolled participants had usable monitoring data, or whether any exclusions were made. Enrollment of 19 is reported, but that figure alone does not establish the number included in any particular analysis. The registry’s zero listed analyses should be understood as an absence of registered analysis entries, not as confirmation that no analysis was conducted outside the registry.
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 |
|---|---|---|---|
| Research Study Participation | 0 | 19 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Research Study Participation | 0 of 19 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Research Study Participation | 0 of 19 |
The registry’s safety entry is under “Research Study Participation.” It reports 19 participants at risk, zero serious adverse events, zero other adverse events, and zero deaths. No serious adverse-event terms are listed. These are the figures recorded for that entry; they do not provide a comparison between treatment groups, and the study is described as observational rather than as a randomized treatment comparison.
In general, a count of zero recorded events does not by itself establish that no event could occur or that monitoring captured every event. Interpretation depends on how events were defined, collected, and followed, and on which participants contributed safety information. The registry record does not report those details. It also does not provide event timing, severity definitions, or further information about safety ascertainment.
The safety counts should be kept separate from the study’s primary cardiovascular measurement. They do not show the level or precision of 24-hour heart rate, and they do not answer whether occupational activity is associated with cardiovascular measures. They are descriptive registry figures rather than a comparative safety analysis.
12. What the Result Does, and Does Not, Mean
The record establishes that the Heart at Work Study was an observational study focused on cardiovascular mechanisms in people with high activity occupations. It identifies 24-hour heart rate as the primary outcome, describes a one-week monitoring period, and names secondary measures related to blood pressure, heart rate variability, and physical activity. It also reports enrollment of 19 and a completed status. These details describe the study’s topic and recorded design features.
The record does not report numerical results for the primary endpoint or listed secondary outcomes. It does not give an estimated mean heart rate, standard error, confidence interval, or statistical test. As a result, it is not possible to determine from the registry record whether heart rate was higher or lower in any group, how large any difference or association might be, or how precisely it was estimated. The same limitation applies to the secondary outcomes.
The observational design also limits the kinds of conclusions that could be drawn even if estimates were available. An association between occupational activity and a cardiovascular measure would not, by itself, demonstrate that occupational activity caused the measured difference. Interpretation would depend on how exposure and outcomes were measured, which comparison was made, participant characteristics, and the statistical model. Those details are not reported in the registry record.
The safety entry records zero serious adverse events, zero other adverse events, and zero deaths among 19 at risk in the Research Study Participation group. Those counts do not amount to a comparison of harms, and the record does not describe event-collection procedures. Taken together, the posted information supports a description of the study’s aims, endpoint definitions, and selected registry fields, but not a conclusion about the direction, size, precision, or causal meaning of any cardiovascular result.
13. Why This Trial Matters Statistically
The study addresses a question about occupational physical activity and cardiovascular measures, with a focus on the possibility that high activity occupations may have cardiovascular consequences. Its statistical interest lies in measuring heart rate and related domains during ordinary daily activity rather than describing only a single measurement. The registry specifies a one-week monitoring period and a primary outcome based on 24-hour heart rate.
From a biostatistical perspective, this makes the definition and handling of repeated measurements important. Daily heart-rate summaries collected across a monitoring period may contain information about both between-person differences and variation within a person over time. General statistical methods need to respect the dependence among repeated observations and match the model to the scientific question. The registry record does not describe those methods, so the analytic approach cannot be evaluated.
The record also illustrates why outcome definitions and results are both needed. Naming a least-squares mean and standard error specifies the intended form of summary, but without the estimates, model details, and uncertainty values, readers cannot assess magnitude or precision. Likewise, listing multiple secondary outcomes clarifies the domains of interest but does not show whether they were analyzed or how multiplicity was addressed.
Finally, the observational design and the registry’s caution about non-comparable arms are central to interpretation. A clearly defined comparison, transparent participant description, and appropriate analysis are needed to distinguish an observed association from a causal effect. The available record identifies an important statistical question, but its listed information does not permit evaluation of an empirical answer.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The main trial-specific limitation is that the registry record contains no numerical outcome results despite marking the study as completed. It lists zero analyses, and does not report the primary heart-rate estimate, standard error, confidence interval, or statistical test. Without these, neither effect magnitude nor precision can be evaluated. The record also does not report numerical results for the listed secondary outcomes.
Details needed to understand the sample and measurements are sparse. Enrollment is listed as 19, but participant characteristics, eligibility criteria, recruitment procedures, and occupations represented are not reported in the registry record. The record describes average heart rate over each 24-hour period during a one-week monitoring period, but does not report the monitoring device, quality-control procedures, completeness of measurement, or how repeated observations were analyzed.
The comparison structure is unclear. The registry says allocation was not stated and warns that arms are not a like-for-like control comparison; the identities and characteristics of any arms are not reported in the registry record. The model, adjustment variables, analytic populations, and handling of missing data are also not reported. These omissions prevent assessment of potential confounding, selection into analyses, and robustness of estimates. The record does not report a multiplicity strategy despite listing 12 outcome measures. These gaps limit interpretation of the registered information; they do not establish that the study team did not collect or analyze further information outside the registry.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Heart at Work Study — NCT04075279.
- Registry record last updated 2021-05-03; status last verified 2021-04.
- Results first posted 2021-05-03.
- 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 Heart at Work Study is an observational study sponsored by the University of Pittsburgh. The registry lists the study as completed, with a start date of 2019-10-17, a primary completion date of 2020-04-20, and enrollment of 19. Its stated aim is to examine cardiovascular mechanisms related to increased cardiovascular mortality among people with high activity occupations.
The primary outcome is 24-hour heart rate in beats per minute, summarized as a least-squares mean with standard error over a one-week monitoring period. Listed secondary outcomes include ambulatory systolic blood pressure, nocturnal heart rate variability, and physical activity measures. The registry lists 12 outcome measures and zero analyses.
No numerical outcome estimates, analysis details, missing-data methods, or multiplicity procedures are reported in the registry record. The safety entry reports zero serious adverse events, zero other adverse events, and zero deaths in the Research Study Participation group, with 19 at risk. The record’s caution that arms are not a like-for-like control comparison is important when considering any potential group contrasts.