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 Targeting Physical Health in Schizophrenia: Physical Activity Can Enhance Life Randomized Control Trial (NCT04173572), a randomized na study. The primary outcome is Difference in Participant's Total Distance During 6-minute Walk.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04173572 |
| Phase | NA |
| Condition | Schizophrenia, Schizoaffective Disorder, Brief Psychotic Disorder |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Triple |
| Enrollment | 50 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of North Carolina, Chapel Hill |
| Results posted | Yes |
2. Clinical Question
Population
The trial concerned people with schizophrenia spectrum disorders. The registry lists Schizophrenia, Schizoaffective Disorder, Brief Psychotic Disorder, Schizophreniform Disorders, and Unspecified Schizophrenia Spectrum and Other Psychotic Disorder. Enrollment was 50. For the primary outcome, the registry says participants from cohorts 2 and 3 were analyzed because cohort 1 was considered not comparable after protocol changes and cancellation following 7 groups at the onset of the COVID-19 pandemic. The registry also notes that participants assessed from home could not provide this measure.
Intervention
The intervention of interest was the Walking Group: supervised virtual walking groups on a secure online platform, along with independent walks at a location of the participant’s choosing. The study description says participants received a Fitbit wristband and were taught to use heart-rate information to guide walking intensity. Group walks began at 15 minutes in the first two weeks and progressed to 30-minute sessions over the intervention.
Comparator
The comparator was Fitbit Alone. Its description says participants received a Fitbit wristband and information on current recommended physical activity guidelines. Study staff might contact participants weekly if it appeared they were not wearing the device; the registry description of this arm is incomplete.
Primary question
The registered primary outcome was the difference in participants’ total distance during the 6-minute walk test, measured in meters at baseline and the last study visit, up to 20 weeks. The record does not report the result of this comparison, including an effect estimate or uncertainty interval. The clinical question can therefore be described from the design and endpoint, but its answer cannot be determined from the registry record.
3. Trial Design
This was a randomized, triple-masked, parallel-group study sponsored by the University of North Carolina, Chapel Hill. The registry lists the phase as NA and the status as completed. The enrollment was 50. The study start date was 2019-12-20, and the primary completion date was 2022-03-23. These dates describe the registered timeline; they do not establish when each participant completed assessments.
The comparison was between a Walking Group and Fitbit Alone. The Walking Group involved supervised virtual walking sessions twice a week and independent walks. The intervention description also discusses use of Fitbit heart-rate information to guide walking intensity and a gradual increase in the duration of group walks. The Fitbit Alone description includes a wristband and information about physical activity guidelines. Further details of that arm are not reported in the registry record because the description ends mid-sentence.
Random allocation means participants are assigned to study groups by chance, which is intended to reduce systematic differences between groups at the outset. A parallel design means participants are assigned to a group and the groups are compared over the study rather than participants crossing between interventions. Triple masking is recorded, but the registry record does not identify which roles were masked or explain how masking was maintained.
The primary outcome was measured at baseline and the last study visit, with a stated timeframe of up to 20 weeks. The record indicates that the primary analysis included cohorts 2 and 3, while cohort 1 was deemed not comparable following protocol changes and cancellation after 7 groups at the onset of the COVID-19 pandemic. How the randomization was conducted within cohorts, and whether allocation was balanced or stratified, is 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.
Before assignment: Participants were randomly assigned to a group by an unblinded research assistant after they were screened as eligible and created a baseline appointment time with the research coordinator.
Overall Study
| Stage | Walking Group | Fitbit Alone |
|---|---|---|
| STARTED | 24 | 26 |
| Cohort 1 | 7 | 6 |
| Cohort 2 | 8 | 12 |
| Cohort 3 | 9 | 8 |
| COMPLETED | 20 | 20 |
| NOT COMPLETED | 4 | 6 |
Reasons for not completing this period:
| Reason | Walking Group | Fitbit Alone |
|---|---|---|
| Withdrawal by Subject | 1 | 5 |
| Lost to Follow-up | 3 | 1 |
Analysis population for the primary outcome, as defined in the registry: Participants were only analyzed from cohorts 2 and 3 as cohort 1 was deemed not comparable (protocol changes \& cancellation after 7 groups due to the onset of the COVID-19 pandemic). Participants who completed assessments from home were unable to provide data on this measure (n=5 in walking group, n=9 in fitbit alone). Post-treatment data are not available for participants who withdrew or were lost to follow-up (n=1 in walking group, n=2 in Fitbit alone).
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 | Walking Group | Fitbit Alone | Total |
|---|---|---|---|---|
| Participants analysed | 24 | 26 | 50 | |
| Age, Continuous | years | 40.38 (22 to 62) | 39.89 (21 to 62) | 40.14 (21 to 62) |
| Sex: Female, Male: Female | Participants | 14 | 11 | 25 |
| Sex: Female, Male: Male | Participants | 10 | 15 | 25 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 4 | 1 | 5 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 20 | 25 | 45 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 3 | 2 | 5 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 7 | 6 | 13 |
| Race (NIH/OMB): White | Participants | 11 | 16 | 27 |
| Race (NIH/OMB): More than one race | Participants | 3 | 2 | 5 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Region of Enrollment: United States | Participants | 24 | 26 | 50 |
| Occupation: Employed | Participants | 7 | 4 | 11 |
| Occupation: Unemployed/Disability | Participants | 17 | 16 | 33 |
| Occupation: Student | Participants | 0 | 6 | 6 |
| MINI - Psychotic Disorders: Lifetime mood disorder w/ psychotic features | Participants | 2 | 2 | 4 |
| MINI - Psychotic Disorders: Current mood disorder w/ psychotic features | Participants | 0 | 0 | 0 |
| MINI - Psychotic Disorders: Lifetime psychotic disorder | Participants | 22 | 25 | 47 |
| MINI - Psychotic Disorders: Current psychotic disorder | Participants | 13 | 13 | 26 |
| WRAT 3 Word Reading Task (Raw Score) | units on a scale | 36.24 (SD 3.49) | 37.05 (SD 3.09) | 36.65 (SD 3.23) |
6. Primary Endpoint
The registry lists the primary outcome as Difference in Participant's Total Distance During 6-minute Walk, measured over Baseline and the last study visit (Up to 20 weeks).
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | meters |
| Endpoint classification | Continuous Endpoint |
The primary endpoint was the difference in participants’ total distance during the 6-minute walk test, expressed in meters. The registry describes the test as continuous walking for six minutes on a flat indoor surface around cones separated by 100ft. It gives a possible distance range of 400 meters to 650 meters and states that higher scores reflect better outcomes, meaning greater physical fitness.
The measure is used to assess cardiorespiratory fitness through a functional walking task. As a continuous outcome, it retains information about the distance achieved rather than reducing performance to a category. Comparing distance from baseline with distance at the last study visit can describe how measured walking capacity changed over the assessment period. A comparison between randomized groups would then estimate the difference in those changes, if that is the analysis conducted; the registry record does not specify the primary analysis method or report its result.
The registry identifies baseline and the last study visit as assessment times, with follow-up up to 20 weeks. It also notes that participants completing assessments from home could not provide data on this measure. The record says the primary outcome analysis used cohorts 2 and 3 and excluded cohort 1 as not comparable. These restrictions matter when interpreting the endpoint: the outcome does not represent every enrolled participant, and the available record does not fully describe the resulting analysis population or missing-data handling.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a clinically interpretable primary outcome: distance walked during the 6-minute walk test, measured in meters. However, it does not report a group contrast, a mean change, a confidence interval, a p-value, or any other primary-outcome result. There is therefore no registry-record estimate from which to describe the magnitude, direction, or precision of the difference between Walking Group and Fitbit Alone.
The test’s stated direction is clear: higher distance reflects greater physical fitness. That direction explains how an outcome estimate would be read, but it does not establish which group had a higher result or whether any observed difference was precise. A confidence interval, if reported, would show a range of values reasonably compatible with the data and analysis assumptions. Without such an interval, the uncertainty around the primary comparison cannot be assessed from the record.
Interpretation is also shaped by the primary analysis population described in the registry. Cohort 1 was considered not comparable after protocol changes and cancellation following 7 groups at the onset of the COVID-19 pandemic; only cohorts 2 and 3 were analyzed for this measure. In addition, participants assessed from home were unable to complete the 6-minute walk test, and the registry notes n=5 in the Walking Group. The available description does not give the corresponding count for Fitbit Alone or the final number analyzed in either group.
The safety counts are separate from the primary efficacy question. The registry reports one serious adverse event among 24 participants at risk in the Walking Group and none among 26 participants at risk in Fitbit Alone. It lists “Hospitalization unrelated to study” as the top serious event term, at 4.2%, and reports no deaths in either group. These counts describe recorded events; they do not supply an estimate of the primary walking-distance difference.
Overall, the record documents the trial’s design, endpoint definition, restrictions on the primary analysis population, and adverse-event counts. It does not report enough primary-outcome statistics to determine the observed group difference or its precision. No conclusion about the intervention’s effect on the registered endpoint can be drawn from the endpoint description alone.
9. Statistical Methods Explained
The registry describes the primary outcome as a mean, with standard deviation as the measure of dispersion. A mean represents the average distance in a group, while a standard deviation describes how spread out individual distances are around that average. These summaries help characterize the observed data, but they do not by themselves establish a between-group effect or its uncertainty. The registry record does not include the primary outcome means, standard deviations, or an analysis estimate.
What a group comparison would mean
For a continuous endpoint such as walking distance, a group comparison can be expressed in the original measurement units. An estimate in meters would describe the average difference between the groups under the chosen analysis. If change from baseline is used, the estimate would compare average changes; if follow-up values are compared with adjustment for baseline, its interpretation would depend on that model. The registry identifies measurements at baseline and the last study visit but does not report which of these approaches was used.
A confidence interval communicates uncertainty around an estimated effect. A narrower interval indicates greater precision under the assumptions of the analysis, while a wider interval indicates less precision. A p-value addresses compatibility of the data with a specified null hypothesis under an analysis model; it does not measure the size or practical importance of an effect. The registry record does not report a confidence interval or p-value for the primary outcome, so neither precision nor statistical evidence for a group difference can be assessed from the posted record.
Randomization and masking
Randomization is intended to make group assignment independent of participants’ measured and unmeasured characteristics, on average. It supports a fair comparison, but it cannot ensure that the groups are identical, especially in a study with limited enrollment. Masking can reduce the influence of expectations or knowledge of assignment on care, measurement, or analysis. The registry labels the study triple-masked but does not explain which people were masked, whether masking remained intact, or how masking was implemented. These details are not reported in the registry record.
Planning illustrations
The registry describes planning illustrations based on a stated fraction of an observed effect, using a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Such illustrations estimate participants per arm for a chosen power under their assumptions; they are not observed power and do not establish the power of the completed trial. They also do not replace a trial’s own design justification. The sample-size justification for this trial is not reported in the registry record. No planning illustration values or observed primary effect are available in the record described for this analysis.
More generally, planning calculations depend on the effect size the study aims to detect, the variability of the outcome, the significance threshold, and the chosen power. Smaller target effects generally require more information to distinguish from random variation, while more variable measurements also reduce precision. These are general statistical principles, not trial-specific findings. They should not be used to infer an intended effect or a design rationale that is absent from the registry record.
Why analysis choices matter
Analysis populations and missing-data procedures affect the meaning of a result. A complete-case analysis uses participants with the necessary measurements, while other approaches may use assumptions or models to account for missing outcomes. Each approach requires transparent reporting of who was included and what assumptions were made. The registry says cohorts 2 and 3 were analyzed for the primary outcome and that some home assessments could not yield a walk-test value, but it does not state the missing-data method or the final analysis counts.
Protocol changes and the exclusion of cohort 1 raise a further interpretive issue: the analysis does not simply describe every participant enrolled across the full study. The registry gives a reason for treating that cohort as not comparable, but does not report details of the changes, the timing of the decision, or sensitivity analyses examining its impact. These are relevant when judging how robust the primary comparison is.
The record lists 17 outcome measures and 22 analyses. When multiple outcomes or analyses are examined, the chance of at least one apparently notable result can increase if each is tested independently without adjustment. Multiplicity procedures can control or describe that concern, but the registry record does not report whether any adjustment was planned or applied. The number of listed measures alone does not reveal which analyses were primary, secondary, exploratory, or included in any multiplicity strategy.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 17 outcome measures and 22 analyses, including the primary 6-minute walk distance outcome and secondary outcomes involving walking minutes, daily steps, loneliness, PANSS score, body mass index, body weight, waist circumference, and systolic blood pressure. Examining multiple outcomes can increase the chance of at least one apparently unusual result when many statistical tests are conducted. Whether and how that concern was handled is not reported in the registry record. The record also does not identify a multiplicity strategy or specify which analyses were designated confirmatory.
Missingness is particularly relevant to the primary endpoint. The registry says participants assessed from home could not provide 6-minute walk test data and notes n=5 in the Walking Group. The count for the Fitbit Alone group, the total number with missing primary measurements, and reasons for other missing measurements are not reported in the registry record. How missing observations were handled, including whether any imputation or sensitivity analysis was used, is also not reported.
The primary analysis population was restricted to cohorts 2 and 3 because cohort 1 was deemed not comparable after protocol changes and cancellation following 7 groups at the onset of the COVID-19 pandemic. The record does not provide the final analyzed sample size by group, a complete participant flow, or a detailed definition of the analysis population. Interim analyses and any stopping rules are not reported in the registry record. These omissions limit assessment of the analysis choices and the extent to which results, if reported elsewhere, would represent all enrolled participants.
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 |
|---|---|---|---|
| Walking Group | 1 | 24 | 4.2% |
| Fitbit Alone | 0 | 26 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Walking Group | 0 of 24 |
| Fitbit Alone | 0 of 26 |
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 |
|---|---|
| Walking Group | 0 of 24 |
| Fitbit Alone | 0 of 26 |
Most frequent serious adverse event terms
| Event term | Organ system | Walking Group | Fitbit Alone |
|---|---|---|---|
| Hospitalization unrelated to study | Psychiatric disorders | 1 of 24 | 0 of 26 |
Serious events with the highest arm-level rate: hospitalization unrelated to study (4.2%).
The registry reports serious adverse events for participants at risk in each group. In the Walking Group, 24 participants were listed as at risk and 1 as affected by a serious adverse event. In Fitbit Alone, 26 were listed as at risk and 0 as affected. The registry reports 0 deaths in both groups. It lists “Hospitalization unrelated to study” as the top serious event term, with 4.2% recorded.
These are event counts, not an estimate of the relative safety of the two approaches. The registry record does not provide detailed event narratives, timing, duration, or a complete account of how the event term relates to the serious-event count. The label “unrelated to study” indicates the registry’s characterization; it does not establish a broader causal assessment. With the information available, the counts should be read descriptively and not as proof that one group is safer.
The adverse-event figures also do not answer the primary question about walking distance. The registry does not report a broader analysis of non-serious events or explain whether all adverse events were collected in the same way across groups. Further safety detail is not reported in the registry record.
12. What the Result Does, and Does Not, Mean
The registry record makes the trial’s central measurement understandable: participants’ distance during a 6-minute walk test was intended to capture cardiorespiratory fitness, with greater distance representing a better score. It also describes a randomized comparison of supervised virtual walking groups plus independent walks against Fitbit Alone. These design details clarify what investigators intended to compare.
They do not establish what the comparison found. The primary outcome result, including the between-group estimate and its precision, is not reported in the registry record. The endpoint definition cannot substitute for an observed result, and the safety counts do not answer the walking-distance question. Any statement that the intervention improved, worsened, or had no effect on the primary outcome would go beyond the recorded results.
The analysis population also requires care in interpretation. The registry states that cohorts 2 and 3 were analyzed for this outcome and cohort 1 was considered not comparable after protocol changes and cancellation following 7 groups at the onset of the COVID-19 pandemic. It further notes that home assessments could not produce the walk-test measure. This means the registered primary outcome population was not simply every participant enrolled, but the final group counts and handling of unavailable measurements are not reported.
In general, a well-reported estimate alongside an uncertainty interval helps readers judge both the likely direction and precision of a group difference. Statistical significance, if reported, would not alone establish the size or practical importance of a difference. Conversely, a non-significant result would not prove that groups were equivalent. Those principles are general; the registry record does not provide the statistics needed to apply them to this trial.
The appropriate conclusion is therefore limited: the record describes the trial design, planned primary measure, analysis-cohort restriction, and serious adverse-event counts, but it does not report the primary outcome result. The record alone cannot support a conclusion about the effect of PACE-Life on walking distance.
13. Why This Trial Matters Statistically
This trial raises several statistical issues that are important in clinical research. The primary measure is a continuous functional outcome, and the registry identifies both its measurement units and the direction of a better score. Clear endpoint definition is essential because it allows readers to understand what an eventual estimate would represent and how to interpret its direction.
The record also makes explicit that the primary outcome population differed from the full enrolled population. Cohort 1 was deemed not comparable after protocol changes and cancellation following 7 groups at the onset of the COVID-19 pandemic. Participants assessed from home could not contribute a walk-test result, with n=5 noted in the Walking Group. Transparent reporting of these restrictions, final analysis counts, and missing-data handling is important for evaluating precision and possible selection effects.
Randomization and masking are important design features, but they do not remove the need for complete outcome reporting. A reader needs the effect estimate and an uncertainty measure to evaluate the result. Neither is reported for the primary outcome in the registry record. The listed 17 outcome measures and 22 analyses also make it relevant to know whether multiplicity was considered, but no such plan is reported.
Finally, the record illustrates the distinction between descriptive safety counts and an efficacy comparison. Serious adverse-event counts are reported, while the primary walking-distance result is not. Statistical interpretation depends on the specific outcome and analysis; one cannot stand in for the other. The central statistical lesson is that design and endpoint details are informative, but they do not replace the estimate, uncertainty, and analysis details required to assess a trial’s primary comparison.
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 outcome result is not reported in the registry record. Without a group estimate and measure of uncertainty, the magnitude and precision of the trial’s primary comparison cannot be assessed. The record also does not give primary outcome means, standard deviations, p-values, confidence intervals, or final numbers analyzed by group.
The primary outcome population was restricted to cohorts 2 and 3 because cohort 1 was deemed not comparable following protocol changes and cancellation after 7 groups at the onset of the COVID-19 pandemic. Details of those protocol changes, the decision process, and any analyses assessing the impact of excluding cohort 1 are not reported. Home assessment prevented some participants from providing the 6-minute walk test; the record notes n=5 in the Walking Group, but does not give a corresponding count for Fitbit Alone or describe other missing observations.
The registry record does not specify the statistical model, whether the primary comparison used change from baseline or adjusted follow-up values, or how missing data were handled. The exact analysis population and participant flow are not reported. It also does not identify the roles masked under the triple-masked designation or report a multiplicity plan despite listing 17 outcome measures and 22 analyses.
Some intervention descriptions are incomplete, including the Fitbit Alone description. These limits restrict assessment of intervention delivery and reproducibility. The registry’s reported serious adverse-event counts are descriptive, with limited detail about event timing and narratives. Collectively, these reporting gaps constrain interpretation of both the primary comparison and the broader trial record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Targeting Physical Health in Schizophrenia: Physical Activity Can Enhance Life Randomized Control Trial — NCT04173572.
- Registry record last updated 2022-09-22; status last verified 2022-03.
- Results first posted 2022-09-22.
- 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 registry describes NCT04173572, a completed randomized, triple-masked, parallel-group trial sponsored by the University of North Carolina, Chapel Hill. Enrollment was 50. The comparison was Walking Group versus Fitbit Alone, and the primary outcome was difference in total distance during the 6-minute walk test, measured at baseline and the last study visit, up to 20 weeks.
The primary analysis included cohorts 2 and 3; cohort 1 was deemed not comparable after protocol changes and cancellation following 7 groups at the onset of the COVID-19 pandemic. The registry notes that home assessments could not provide the walk-test measure, including n=5 in the Walking Group. The primary outcome result and its statistical uncertainty are not reported in the registry record.
For serious adverse events, the record lists 1 affected participant among 24 at risk in the Walking Group and 0 among 26 in Fitbit Alone; deaths were 0 in both groups. The top serious event term is listed as “Hospitalization unrelated to study” at 4.2%.