Home-based Leg Heat Therapy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Home-based Leg Heat Therapy (NCT03763331), a randomized na study. The primary outcome is Change in 6-min Walk Distance.

2. Clinical Question

The clinical question is about change in walking distance over the study period, comparing a daily home-based heat intervention with a thermoneutral control. Random assignment is intended to create groups that are comparable on average, so that differences between groups can be interpreted in light of the assigned interventions. In a small trial, however, chance differences between groups may remain, and estimates may be imprecise.

The registry describes the study objective more broadly as evaluating vascular function, walking tolerance, and quality of life. The posted primary measure is the change in 6-minute walk distance. Other outcomes include treadmill walking time, calf blood flow, leg cutaneous vascular conductance, and questionnaire scores. Numeric results are posted for three secondary outcomes; results for the other listed secondary outcomes are not reported in the registry record.

The record reports 34 participants enrolled, while the primary outcome results list 14 participants in the sham group and 15 in the heat therapy group. The reason that the outcome counts differ from the enrollment figure is not reported in the registry record. The primary question is therefore best read as a comparison of the available posted outcome summaries, not as a complete account of every enrolled participant's follow-up.

3. Trial Design

This was a randomized, single-masked, parallel-group study of home-based leg heat therapy in patients with symptomatic peripheral arterial disease. The registry lists Indiana University as the sponsor and gives the study status as completed. The listed study start was 2019-01-14, and primary completion was 2021-06-21. The study phase is listed as not applicable.

Participants were assigned to heat therapy or a sham treatment. Both interventions used water-circulating trousers connected to a pump, with a daily session lasting 90 minutes for 8 weeks. The sham circulated water at 91.4 degrees F. The heat therapy description specifies water at 110 degrees F. The design description identifies the study as single-masked, but which participants or study personnel were masked is not reported in the registry record.

The registry reports 34 participants enrolled. For the primary outcome, the posted results include 14 participants in the sham group and 15 in the heat therapy group. Counts for the posted secondary outcomes vary: the treadmill walking-time and leg cutaneous vascular conductance summaries include 14 sham and 15 heat therapy participants, while the calf blood-flow summaries include 11 participants in each group. The reasons for these differences in outcome counts are not reported in the registry record.

The registry describes the primary outcome as change in 6-minute walk distance from baseline to the 8-week follow-up. It is reported as a median with an interquartile range. Secondary outcomes include change in treadmill peak walking time, peak calf blood flow, leg cutaneous vascular conductance, the Vascular Quality of Life Questionnaire-6 score, and the Short Form 36 physical functioning score. Numeric results are posted for the first three of these secondary outcomes. Results for the questionnaire outcomes are not reported in the registry record.

Further details about sequence generation, allocation concealment, the identity of the masked group, adherence, and the planned statistical analysis are not reported in the registry record. The enrollment figure alone does not establish the basis for the study's sample size or whether it was designed to detect a particular effect.

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: A total of 542 patients were referred and screened for the study. Four hundred and twenty-eight participants were deemed ineligible and 80 refused to participate. The remaining 34 patients were randomly allocated to receive HT (n = 18) or the control treatment (n = 16).

Overall Study

Reasons for not completing this period:

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.

Population: Baseline characteristics of participants with PAD that completed the 8-wk intervention.

6. Primary Endpoint

The registry lists the primary outcome as Change in 6-min Walk Distance, measured over 8 weeks.

The primary endpoint is change in 6-minute walk distance, measured in meters, from baseline to the 8-week follow-up. The 6-minute walk test records the distance a participant walks during a fixed period. As a general statistical and clinical concept, a timed walking test can provide a standardized measure of functional walking capacity; it is distinct from a measure of vascular function at rest or a questionnaire about quality of life.

The registry reports the primary outcome as a median and interquartile range rather than a mean and standard deviation. The sham group median change was -0.9 meters, with an interquartile range from -5.8 to 14.3. The heat therapy group median change was 21.3 meters, with an interquartile range from 10.1 to 42.4. The median describes the middle of the observed group values, while the interquartile range describes the span from the lower to the upper quartile. In general, this summary is useful when the distribution may not be well represented by a mean alone.

The endpoint is expressed as change from baseline, so the reported summaries concern within-participant change over the study period, summarized separately by group. The record does not post an inferential comparison between groups for this primary endpoint, such as a difference in medians, a confidence interval, or a p-value. It also does not report the individual-level distribution or the method used to handle missing follow-up measurements. The group summaries therefore describe the recorded changes but do not, by themselves, quantify the uncertainty in a between-group effect.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome and the posted secondary outcomes use different statistical summaries. The primary 6-minute walk result is reported as a median and interquartile range. The secondary continuous outcomes are reported as means and standard deviations. These summaries answer related but distinct descriptive questions, and their results should not be compared as though they were measured on the same scale or summarized in the same way.

What does a median and interquartile range describe?

The median is the middle value when observations are ordered. It is less influenced by unusually high or low observations than the mean. The interquartile range spans the middle half of the observations, from the lower quartile to the upper quartile. It conveys the spread of the central part of the observed distribution, but it is not a confidence interval for the median or for a treatment contrast. The registry does not report an inferential interval for the primary endpoint.

For the primary endpoint, the registry reports a median change of -0.9 meters in the sham group and 21.3 meters in the heat therapy group, with respective interquartile ranges of -5.8 to 14.3 and 10.1 to 42.4. These summaries describe the observed group changes. They do not directly estimate the uncertainty in the difference between groups. A formal comparison could use an analysis appropriate to the endpoint and study design, but the method used for the primary comparison is not reported in the registry record.

How should the secondary mean differences be read?

For the secondary outcomes with numeric results, the posted means describe average change in each group. The mean difference is the unadjusted contrast between the heat therapy and sham group means, with positive estimates indicating a larger numerical change in the heat therapy group under the reported contrast direction. A mean difference is expressed in the outcome's units, so its magnitude is specific to that outcome. The comparisons are recalculated from the posted group summaries; they are not listed as reported sponsor analyses.

The intervals attached to the secondary mean differences express uncertainty around those estimates under the recalculation method. The confidence level for these intervals is not reported in the registry record, so they should not be labeled as a particular confidence level. In general, a confidence interval is a range generated by a statistical procedure that reflects the estimate's uncertainty under specified assumptions. An interval including zero does not demonstrate equivalence or rule out potentially meaningful differences; it indicates that the data and method do not isolate a difference from no difference at the interval's stated level.

The unadjusted p-values for the three posted secondary comparisons are 0.195, 0.787, and 0.735. A p-value describes how compatible the observed data are with a null hypothesis under a particular statistical model; it is not the probability that the null hypothesis is true, nor does it measure the clinical importance of an estimate. The registry does not report a multiplicity adjustment or the prespecified role of these secondary tests. Their p-values should therefore be treated as exploratory, unadjusted summaries rather than definitive evidence.

Why does variability matter?

The secondary summaries include standard deviations, which describe the observed spread of participant changes around each group mean. In general, larger variability makes an estimate less precise when other aspects of the study are unchanged. Here the outcome counts are modest and differ across outcomes, and the reported intervals for the secondary contrasts are broad enough to include zero. The precision of any comparison depends on both the variability and the number of observations contributing to that outcome.

Over-dispersion is a general concern when the observed variability is greater than a statistical model expects. A model that understates variability can produce intervals that are too narrow and p-values that are too small. The registry does not report a dispersion assessment or a model-based variance adjustment for these outcomes. The posted standard deviations do provide a descriptive view of spread, but they do not reveal the full shape of each outcome distribution or verify model assumptions.

What do planning illustrations mean?

The sample-size illustrations are based on the observed secondary effects, with a two-sided significance level of 0.05, equal allocation between groups, and a normal approximation. Their effect assumptions use stated fractions of the observed effect. These are planning illustrations, not the study's original sample-size justification and not observed power. The registry does not report the trial's own sample-size justification, so the illustrations cannot establish what the investigators planned or whether the trial met a prespecified target.

In general, a planning calculation estimates the number of participants per arm needed under its stated assumptions to detect a selected effect with a selected power. The result depends on the effect assumed, variability, significance level, allocation, and statistical method. Because the illustrations use effects observed in this small study, they are especially sensitive to uncertainty in those estimates. They should not be read as evidence that a particular effect is real or as a measure of the probability that the study detected it.

The primary endpoint does not have a posted between-group comparison or a corresponding planning illustration in the listed results. The sample-size illustrations concern the secondary comparisons and cannot be transferred to the primary outcome without additional assumptions and a specified primary analysis. The registry does not report whether interim analyses were planned or conducted, or whether any adjustment was made for multiple outcomes.

What can be inferred from the posted analyses?

The record lists no reported analyses. The secondary comparisons are simple unadjusted recalculations from the posted summary statistics. They do not incorporate adjustment for baseline covariates, repeated measurements, or multiplicity. Whether any of those approaches was used by the study investigators is not reported in the registry record. Since there is no stated discrepancy between a sponsor analysis and the recalculations, the posted summaries can be described as they appear, while keeping their unadjusted status clear.

General statistical interpretation also depends on how missing measurements, protocol deviations, and the analysis population were handled. Those details are not reported in the registry record. The results should therefore be read as summaries of the available posted observations, without assuming an intention-to-treat analysis, a per-protocol analysis, or a particular missing-data method.

10. Multiplicity, Missing Data and Analysis Populations

The registry identifies one primary outcome and several secondary outcomes, but the statistical plan for evaluating them is not reported in the registry record. There is no posted account of whether outcomes were tested in a hierarchy, whether a family of hypotheses was defined, or whether any multiplicity adjustment was planned or applied. The three posted secondary p-values are unadjusted. Their interpretation should account for the fact that multiple outcomes are listed, without assuming a particular testing strategy.

Multiplicity matters in general because testing several outcomes can raise the chance of at least one apparently small p-value under a collection of null hypotheses. Adjustments can control that risk, but they may also change the precision and interpretation of individual tests. The record does not establish which approach, if any, was intended for this study. The unadjusted secondary results should therefore be treated as exploratory rather than as a set of independently confirmed findings.

There is also limited information about missing outcomes and analysis populations. The study reports 34 participants enrolled, while the primary outcome results list 14 participants in the sham group and 15 in the heat therapy group. Counts for the secondary results vary by outcome. Reasons for these differences, the amount and pattern of missing data, and any imputation or other missing-data method are not reported in the registry record.

The registry does not state whether results are based on all randomized participants, participants with available measurements, or another analysis population. It does not report how protocol deviations were handled or whether the analysis followed the assigned groups regardless of adherence. These details matter because the population included in an analysis can affect both the estimate and its general interpretation. No assumptions about intention-to-treat or per-protocol analysis should be made from the posted summaries alone.

Interim analyses and any related adjustment are also not reported in the registry record. The available information is insufficient to determine whether interim looks at the data occurred. In general, repeated testing over time can affect error rates unless handled in the analysis plan. Without a reported plan, the scope of any such issue cannot be assessed for this trial.

11. 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 non-serious adverse event terms

The adverse-event record reports no serious adverse events in either group and no deaths in either group. Serious adverse events were assessed among 16 participants at risk in the sham group and 18 in the heat therapy group. The registry lists no serious event terms. These are the posted serious-event counts for the study record; they do not establish that the risk of serious events is identical between groups.

For other adverse events, the record reports 0 among 16 participants at risk in the sham group and 4 among 18 at risk in the heat therapy group. The registry does not provide further event descriptions or severity details in the listed results. These counts should be read as recorded events over the study period, not as a comparative risk estimate. No percentage or statistical comparison is reported in the registry record.

In general, small studies and short follow-up can provide limited information about uncommon harms. A count of zero observed events does not prove that an event cannot occur; it means none was recorded in the listed group during the period represented. The adverse-event information should be interpreted alongside the limited outcome counts and the registry's reporting, without inferring safety beyond those data.

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

The registry record describes a randomized comparison of home-based heat therapy with a thermoneutral sham over 8 weeks. For the primary outcome, the posted group summaries show a median change in 6-minute walk distance of -0.9 meters in the sham group and 21.3 meters in the heat therapy group. The interquartile ranges describe the spread of changes within each group. The record does not report a primary between-group estimate or an inferential test, so the observed difference between group medians is not, on its own, a quantified treatment effect.

The available secondary comparisons are unadjusted recalculations from group summary statistics. Their intervals include zero, and their p-values are unadjusted. These results do not establish that the groups differ, but they also do not demonstrate equivalence or rule out effects that the study could estimate only imprecisely. The registry's sample-size illustrations are planning calculations based on observed secondary effects; they are not observed power and do not describe the original design justification.

In general, randomization supports a fair comparison by reducing systematic differences in assigned groups, but it does not eliminate chance imbalance, missing outcome data, or uncertainty. Interpretation is constrained by the absence of a reported primary comparison, the differences in outcome counts, and the lack of information on missing-data methods, analysis populations, and multiplicity handling. The record also does not provide numeric results for all listed secondary outcomes.

The results do not establish that heat therapy improves walking distance or any other outcome, and they do not establish that it has no effect. They describe the observations posted in the registry and leave substantial questions about the precision and analysis of between-group differences. No medical decision should be based on these summaries alone.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of why descriptive group summaries and a direct treatment comparison are not interchangeable. The primary outcome is reported using medians and interquartile ranges, but the registry does not post a primary between-group estimate, uncertainty interval, or p-value. Readers can see the group-level changes, yet cannot assess the uncertainty in the primary contrast from the registry results alone.

The record also illustrates the importance of tracking outcome-specific counts. The primary results list 14 sham and 15 heat therapy participants, and the counts contributing to secondary results differ across outcomes. Without an account of missing observations or analysis populations, it is not possible to determine why the counts vary or how the results represent the randomized groups.

Secondary analyses add context, but they do not replace the primary comparison. The posted secondary results are unadjusted recalculations, and no multiplicity plan is reported. Their intervals include zero, emphasizing the difference between an observed point estimate and a precise conclusion. The sample-size illustrations offer planning scenarios based on observed secondary effects, not evidence of achieved power or the study's original design rationale.

These reporting features matter broadly for clinical research: estimates need a clear comparator, uncertainty, analysis population, and explanation of how multiple outcomes and missing data were handled. The registry record documents the intervention and several outcome summaries, while leaving important parts of the inferential analysis unspecified. Distinguishing what is described from what remains uncertain is central to interpreting a small randomized study responsibly.

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.

Several limitations specific to this record constrain interpretation. The primary outcome is posted as a median and interquartile range for each group, without a reported between-group effect estimate, interval, or p-value. The numerical difference in group medians therefore cannot be read as a formal statistical comparison. The registry does not report the method used to analyze the primary endpoint.

The outcome counts are lower than the enrollment figure and vary among outcomes. The reason for the differences is not reported in the registry record. Missingness could affect interpretation, but the available information does not establish whether measurements were unavailable, excluded, or handled in another way. The analysis population and missing-data approach are also not reported.

Only three of the five listed secondary outcomes have numeric results in the record. The posted secondary contrasts are unadjusted recalculations, and the registry does not describe a multiplicity plan, a prespecified hierarchy of outcomes, or an adjusted analysis. Their intervals include zero, and the interval confidence level is not reported. The small outcome counts and the observed variability limit precision.

Further design and implementation details are not reported in the registry record, including allocation concealment, who was masked, adherence to daily sessions, and whether interim analyses occurred. The registry does not report the trial's sample-size justification or a complete statistical analysis plan. The listed planning illustrations use observed secondary effects and should not be mistaken for the original design calculation.

The safety record gives counts but limited event detail. It does not report a comparative safety analysis, and the available counts alone cannot establish the full safety profile. These limitations are reasons to interpret the posted results as descriptive and incomplete rather than as a definitive account of treatment effects.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Home-based Leg Heat Therapy — NCT03763331.
• Registry record last updated 2023-03-01; status last verified 2023-02.
• Results first posted 2023-03-01.
• 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.

18. Record Summary

NCT03763331, Home-based Leg Heat Therapy, is a completed randomized, single-masked, parallel-group study sponsored by Indiana University. It enrolled 34 participants with symptomatic peripheral arterial disease. The intervention was home-based water-circulating trouser therapy for 90 minutes daily for 8 weeks, using water at 110 degrees F for heat therapy and 91.4 degrees F for sham treatment.

The primary outcome was change in 6-minute walk distance from baseline to the 8-week follow-up. The registry reports group medians and interquartile ranges, but not a primary between-group analysis. Numeric results are posted for three secondary outcomes; two listed questionnaire outcomes have no numeric results in the registry record. Secondary comparisons are unadjusted recalculations and should be interpreted cautiously. The registry does not report the analysis plan, missing-data methods, or multiplicity handling.

No serious adverse events or deaths were recorded in either group in the posted results. Other adverse events were recorded in the heat therapy group, with none recorded in the sham group. The available safety counts and outcome summaries do not establish a definitive treatment effect or comprehensive safety profile.