The Trajectory of Physical Activity Following Pulmonary Rehabilitation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Trajectory of Physical Activity Following Pulmonary Rehabilitation (NCT02399254), a registered phase not stated study. The primary outcome is Minutes/Day at 12 Weeks.

2. Clinical Question

The clinical motivation described in the registry is that greater exercise capacity after pulmonary rehabilitation may not immediately translate into more physical activity at home or in the community. The investigators planned to use motion detectors to measure activity directly and then follow its trajectory. That makes the study question different from asking whether rehabilitation improves exercise capacity: the primary endpoint concerns walking activity in daily life, as measured by the device.

Because no control group is described and no primary outcome estimate is reported, the record cannot establish how the measured activity changed or whether any change was attributable to rehabilitation. It documents the measurement question and the study population, but does not report a result that answers the question.

3. Trial Design

The registry describes a completed study titled “The Trajectory of Physical Activity Following Pulmonary Rehabilitation.” It lists COPD and chronic obstructive pulmonary disease as the conditions under study and names Trinity Health Of New England as the sponsor. The recorded start is 2015-04, the primary completion date is 2017-06-15, and the status is COMPLETED. Enrollment is listed as 21.

One arm is described: Pulmonary Rehabilitation, consisting of patients with COPD following pulmonary rehabilitation. The record does not describe a control arm or a randomized allocation. Allocation is not stated, and the study is not a like-for-like control comparison. The primary endpoint is therefore framed as a within-participant comparison of measured walking activity at baseline and the 12 ± 3 week assessment, not as a between-group treatment contrast.

The primary measure is minutes per day of walking activity recorded by the DynaPort. The stated timeframe is 12 weeks compared with baseline. The registry also lists activity-related energy expenditure at 12 weeks and 48 weeks as secondary outcomes. The study description says investigators intended to examine the subsequent trajectory over several months, but the registry record does not give detailed visit schedules beyond the listed outcome timeframes.

Valid activity data were difficult to obtain at all sites, despite support from the device manufacturer. The primary outcome description states that data had to be uploaded to the manufacturer and then downloaded to the site, and that 16 participants could be analyzed at week 12. The record does not explain the status of each participant without analyzable week-12 data.

Although four outcome measures are listed, the registry reports no analyses. It does not provide outcome estimates, measures of uncertainty, or a statistical analysis plan. Consequently, the design and measurement objectives can be described, but the results and the approach used to analyze them cannot be evaluated from 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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Obtaining valid activity data (uploaded to the manufacturer then downloaded to the site) was a problem at all sites despite good support from the manufacturer. As a result a N of 16 could be analyzed at week 12.

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 Minutes/Day at 12 Weeks, measured over 12 weeks compared to baseline.

The primary endpoint is minutes per day of walking activity, measured directly with the DynaPort. The registry specifies a comparison between baseline and the assessment at 12 ± 3 weeks. This is a continuous measure: it represents an amount of time, rather than a category such as whether a participant did or did not walk.

Direct measurement is relevant to the study’s stated question because the investigators were interested in activity in home and community settings, not only exercise capacity. A motion detector can record walking activity outside a supervised assessment, providing a measure intended to reflect day-to-day behavior. The registry does not provide further information about device wear requirements, processing rules, or how valid recordings were defined.

The planned summary is a mean, with standard error named as the dispersion measure. A mean describes the average observed activity in the analyzed group. Standard error describes the precision of an estimated mean; it is not the same as the spread of individual participants’ activity values. The record does not report the mean change, its standard error, a confidence interval, or a test result. It therefore does not show whether walking activity increased or decreased, nor how precisely any change was estimated.

The primary endpoint covers the week-12 comparison. It does not, by itself, describe the longer trajectory. Activity-related energy expenditure is separately listed at 12 and 48 weeks, but the registry record does not report those results either.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a continuous measure summarized as a mean. For a continuous endpoint, a mean gives the average value in the analyzed observations, while individual values may vary around it. The registry names standard error as the dispersion measure. In general, standard error describes uncertainty in an estimated mean, whereas standard deviation describes the spread of individual observations. These quantities answer different questions and should not be treated as interchangeable. No numerical mean or standard error is reported for the primary endpoint.

What does the baseline comparison estimate?

The stated primary timeframe compares walking activity at baseline with activity at 12 ± 3 weeks. A within-group change describes how the measured outcome differs across those assessments for the analyzed participants. It is not the same as a treatment effect from a randomized comparison. In general, a control group can help distinguish changes associated with an intervention from changes that might occur over time for other reasons. No control group is described in this registry record, and the allocation method is not stated.

The registry specifies minutes per day of walking activity measured by the DynaPort. The primary endpoint description says valid activity data were a challenge because data had to be uploaded to the manufacturer and then downloaded to the site. Direct measurement can reduce reliance on a participant’s recollection, but device data still depend on usable recordings and the rules used to determine validity. Those rules are not reported in the registry record.

How should uncertainty be read?

In general, a confidence interval expresses the range of values reasonably compatible with an estimate under the statistical model. A narrow interval indicates greater precision than a wide interval, but precision is distinct from whether a result is clinically important. A p-value addresses compatibility with a specified null hypothesis under a model; it does not measure the size or importance of an effect. The registry record reports no confidence interval, p-value, or estimated primary change, so these features cannot be assessed for this study.

The record lists four outcome measures and reports zero analyses. That means the registry does not supply an analysis result to interpret. It also does not describe whether the investigators planned a particular test, adjustment, or model for repeated measurements. The analysis plan, including any treatment of baseline values or follow-up time, is not reported in the registry record.

Why does missing-data handling matter?

The primary endpoint description states that valid activity data could be analyzed for 16 participants at week 12, while the enrollment is listed as 21. It also reports problems obtaining valid activity data at all sites. In general, missing outcome data can reduce precision and can introduce bias if the reasons for missingness are related to the outcome or differ across participants. An analysis limited to participants with usable recordings may describe that analyzed group, but its relevance to all enrolled participants depends in part on why data are missing. The record does not state whether investigators used imputation, sensitivity analyses, or another approach.

The number of analyzable observations is not itself an explanation of missingness. The registry does not report the number with valid baseline data, the reasons for unavailable data at each time, or a prespecified analysis population. It also does not state whether participants were included according to an intention-to-treat principle or another rule. Those omissions limit assessment of how the analyzed results, if available, would relate to the enrolled group.

What do the planning assumptions mean?

Any sample-size figures described as planning illustrations are not observed power and are not evidence that the study had adequate power. The stated illustration assumptions use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. Those assumptions describe a hypothetical planning exercise, not the reported design: the registry describes one study arm and a baseline-to-follow-up comparison, rather than two randomized arms. The record does not report the trial’s own sample-size justification, so the illustration should not be mistaken for the original design calculation.

In general, power calculations depend on the target effect, outcome variability, analysis method, and planned allocation. If an effect used for planning is estimated from observed data, that estimate can itself be uncertain. Planning at a fraction of an observed effect explores alternative target sizes; it does not establish the probability that the completed study detected an effect. No sample-size justification or interim-analysis plan is reported in the registry record.

Activity-related energy expenditure is listed as a secondary outcome at 12 and 48 weeks. Repeated measurements can be analyzed in different ways, depending on the question and the assumptions about within-participant correlation and missing observations. The registry does not describe the model, contrasts, or variance assumptions used for these outcomes. Since no analyses or results are posted, it is not possible to determine how the investigators handled the repeated follow-up measures.

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("Pulmonary Rehabilitation")
n   <- c(16)
m   <- c(1.3125)
sp  <- c(0.740038)
sd  <- sp * sqrt(n)      # standard errors converted to SDs
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  Pulmonary Rehabilitation  16  1.312  2.960  -0.265  2.890

11. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures: the primary measure of walking minutes per day at 12 weeks and secondary measures of activity-related energy expenditure at 12 and 48 weeks, alongside the other outcome measures counted in the record. It reports no analyses. The registry record does not describe a multiplicity strategy, such as a hierarchy of hypotheses or adjustment of significance thresholds. Without that information, the intended role of each outcome in drawing conclusions is unclear.

When several outcomes or time points are examined, the chance of at least one apparently unusual result can increase if each is tested separately. In general, prespecifying a primary endpoint and a plan for secondary outcomes helps clarify which findings are confirmatory and which are exploratory. The registry identifies a primary endpoint, but it does not report a statistical analysis plan or any outcome estimates. It is therefore not possible to tell how multiplicity was handled in the completed study.

Missing activity data are explicitly noted. Valid recordings were difficult to obtain at all sites despite manufacturer support, and the registry states that 16 participants could be analyzed at week 12. The record does not report the reasons for missing measurements by participant, whether baseline and follow-up data were both required, or whether a missing-data method was used. It also does not describe sensitivity analyses assessing how assumptions about missing observations might affect results.

The analysis population is not defined beyond the statement about week-12 data that could be analyzed. The registry does not report whether all enrolled participants were included in any analysis, how exclusions were determined, or whether outcomes were analyzed according to a prespecified population. These omissions matter because an analysis restricted to participants with valid device data may not represent all enrolled participants if availability is related to activity or health. The degree and direction of any resulting bias cannot be determined from the record.

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.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: copd exacerbation (33.3%), diarrhea (4.8%), pneumonia (4.8%), cholelithiasis (4.8%), deep vein thrombosis (4.8%).

The registry lists 21 people at risk in the Pulmonary Rehabilitation group. It records 10 affected by serious adverse events, 0 affected by other adverse events, and 0 deaths. These are the adverse-event fields in the record; they do not provide a comparison with an untreated or control group.

The listed serious-event terms are COPD exacerbation at 33.3%, followed by Diarrhea, Pneumonia, Cholelithiasis, and Deep Vein Thrombosis, each at 4.8%. These percentages should be read as the registry’s reported figures for the named terms, not as evidence that rehabilitation caused the events. The record does not provide detail on event timing, severity beyond the serious-event classification, relatedness assessments, or how events were attributed.

Adverse-event counts describe what was recorded during the study, but a count alone does not establish whether an event is more or less frequent than it would have been without the intervention. With no like-for-like comparator described, these figures cannot support a comparative safety estimate. The registry record also does not explain whether multiple event types could be recorded for the same participant, so event terms should not be treated as mutually exclusive categories.

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

The study addresses a practical measurement question: whether physical activity, specifically walking time in daily life, changes after pulmonary rehabilitation and how activity develops over the following months. Its use of a motion detector was intended to capture activity directly rather than relying only on exercise-capacity measures. The registry also documents difficulty obtaining valid activity data, an important issue for studies that depend on device recordings.

However, the registry record does not report the primary outcome results. It gives no mean walking time, mean change, uncertainty interval, or statistical test. There is therefore no posted estimate from which to judge whether activity changed, how large any change was, or how precisely it was measured. The secondary activity-related energy expenditure results are also not reported.

The study design described does not include a like-for-like control group, and the allocation method is not stated. Even if a change over time had been reported, a baseline-to-follow-up comparison in one group would not, on its own, isolate the effect of pulmonary rehabilitation from other influences on activity. The registry record does not establish a causal effect.

The outcome’s availability also limits what can be inferred. The record says that valid activity data could be analyzed for 16 participants at week 12, and that obtaining valid data was a problem at all sites. It does not describe the reasons for unavailable data or the method used to handle missing observations. The extent to which analyzed measurements represent all enrolled participants cannot be determined.

Accordingly, the record is informative about the intended endpoint, the follow-up question, and a practical data-collection challenge. It does not establish whether physical activity increased, decreased, or stayed stable after rehabilitation, whether any change persisted, or whether observed events were caused by the intervention.

14. Why This Trial Matters Statistically

This study is statistically relevant because it distinguishes exercise capacity from activity in everyday settings. Those concepts are related but not identical: a person’s capacity during an exercise assessment does not directly describe how much walking occurs at home or in the community. Measuring walking minutes per day targets that behavioral question more directly.

The use of motion detectors also brings a measurement lesson. Objective recording can create detailed observations, but the value of those observations depends on obtaining valid data and defining what counts as usable. The registry reports difficulty obtaining valid activity data at all sites despite manufacturer support, and identifies 16 participants whose week-12 data could be analyzed. This makes data completeness central to interpreting any result.

The design illustrates the limits of a within-group before-and-after comparison. Such a comparison can describe change over time, but without a control group it cannot separate an intervention-related change from other changes occurring during follow-up. The registry’s stated focus on the trajectory after rehabilitation is useful for framing a longitudinal question, while the absence of reported results and a control comparison constrains conclusions.

Finally, the record makes clear why complete outcome reporting matters. It identifies a primary measure and secondary time points, but reports no analyses or outcome estimates. Without results and uncertainty measures, readers cannot assess the size, precision, or consistency of observed changes. The study’s stated aims remain relevant, but the registry entry does not provide the evidence needed to answer them.

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 immediate limitation for interpretation is that the registry record contains no primary or secondary outcome estimates. It does not report changes in walking minutes per day or activity-related energy expenditure, nor does it report uncertainty measures or statistical tests. The study’s completed status does not fill this reporting gap.

The study is not described as a randomized comparison, and no control group is identified. The allocation method is not stated. A baseline-to-follow-up comparison can describe temporal change in the observed group, but it cannot by itself distinguish changes associated with rehabilitation from other influences over time.

Data collection is another specific limitation. The registry reports that valid activity data were difficult to obtain at all sites despite support from the manufacturer, and that 16 participants could be analyzed at week 12. It does not give reasons for unavailable recordings, details of the validity criteria, or a missing-data method. This leaves uncertainty about selection into the analyzed observations and the representativeness of the week-12 data.

The registry does not describe the rehabilitation program in enough detail to assess variation in its delivery, nor does it give a statistical analysis plan, a sample-size justification, or a multiplicity approach. It lists secondary activity-related energy expenditure outcomes at 12 and 48 weeks, but does not report how repeated measurements were modeled or how missing follow-up observations were addressed.

These limits do not negate the study’s measurement aim, but they restrict what can be concluded from its registry entry. The outcome trajectory, the precision of any estimated change, and the relationship of adverse events to rehabilitation are not established by the information reported.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: The Trajectory of Physical Activity Following Pulmonary Rehabilitation — NCT02399254.
• Registry record last updated 2019-08-06; status last verified 2019-04.
• Results first posted 2019-07-08.
• 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

The registry record describes a completed study of physical activity after pulmonary rehabilitation in people with COPD, sponsored by Trinity Health Of New England. Enrollment is listed as 21. The primary outcome is directly measured walking activity in minutes per day, comparing baseline with the 12 ± 3 week assessment. Activity-related energy expenditure at 12 and 48 weeks is listed as a secondary outcome.

The study description notes difficulty obtaining valid activity data at all sites and states that 16 participants could be analyzed at week 12. No outcome analyses or results are reported. A single pulmonary rehabilitation group is described, with no like-for-like control comparison. The record therefore documents the study question and data-collection challenge but does not establish the direction, size, or precision of changes in physical activity.