Exercise Dose and Metformin for Vascular Health in Metabolic Syndrome: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Exercise Dose and Metformin for Vascular Health in Metabolic Syndrome (NCT03355469), a randomized phase 2, phase 3 study. The primary outcome is Change in Fasting Unscaled Flow Mediated Dilation (FMD) of the Brachial Artery.

2. Clinical Question

3. Trial Design

The registry describes a randomized, parallel-group trial with quadruple masking. It lists the study as phase 2 and phase 3, with an enrollment of 91 and a completed status. The sponsor was Rutgers University. The listed condition was metabolic syndrome.

Participants were assigned among four combinations: low-intensity exercise with placebo, high-intensity exercise with placebo, low-intensity exercise with metformin, and high-intensity exercise with metformin. This arrangement permits comparisons that vary exercise intensity while holding the medication assignment the same, and comparisons that vary medication while holding exercise intensity the same. It also permits comparisons in which both components differ. The registry does not report further details about how randomization was carried out or how masking was maintained.

The primary outcome was measured at baseline and week 16, with change defined as week 16 minus week 0. The registry describes the endpoint analysis population as individuals with both pre- and post-intervention data. The arm-level primary outcome summaries list 12 participants for low-intensity exercise with placebo, 11 for high-intensity exercise with placebo, 16 for low-intensity exercise with metformin, and 9 for high-intensity exercise with metformin. These are the counts attached to the outcome summaries, not the overall enrollment.

The record lists six outcome measures and five posted secondary outcomes. The secondary outcomes include metabolic insulin sensitivity, fasting augmentation index, and insulin-stimulated forearm microvascular blood flow, flow velocity, and blood volume. The registry record does not report the study’s sample-size justification, detailed allocation procedures, or a full statistical analysis plan.

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: Analysis includes only individuals that had both pre and post data.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Change in Fasting Unscaled Flow Mediated Dilation (FMD) of the Brachial Artery, measured over 0 and 16 weeks.

The primary endpoint was change in fasting, unscaled flow-mediated dilation (FMD) of the brachial artery. The registry describes FMD as the percentage change in brachial artery diameter from baseline to deflation, measured five minutes after the artery was occluded by inflating a blood pressure cuff. Change was calculated as the week 16 value minus the week 0 value.

FMD is used in this study as a measure of endothelial function. In general, the measure captures the artery’s change in diameter in response to the procedure described in the registry. The record states that higher values and positive change scores following the intervention indicate a better outcome. This definition supports interpretation of the arm-level changes, but it does not by itself establish that a particular difference is clinically important.

The posted arm summaries are means, with 95% confidence intervals. For low-intensity exercise with placebo, the mean change was -0.45, with a 95% confidence interval from -3.47 to 2.56. For high-intensity exercise with placebo, it was 0.76, with an interval from -4.17 to 5.7. For low-intensity exercise with metformin, it was 3.5, with an interval from 0.65 to 6.46. For high-intensity exercise with metformin, it was 5.28, with an interval from 0.67 to 9.88. These are within-arm summaries; the registry’s adjusted pairwise comparisons are separate analyses.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: it is measured on a numerical scale and summarized as a mean. The registry reports the mean change within each arm and a 95% confidence interval. General statistical point: a confidence interval describes the uncertainty around an estimate under the assumptions of the analysis. A narrower interval indicates greater precision than a wider interval, while an interval that includes zero is compatible with no mean change as well as changes in either direction. It does not mean that every value within the interval is equally likely, nor does it directly give the probability that the true value is inside the interval.

The arm-level summaries and the pairwise comparisons answer different questions. An arm mean describes average change within that group. The reported pairwise ANCOVA analyses compare final values between two groups, using analysis of covariance. In general, ANCOVA estimates a group contrast while accounting for one or more covariates. The registry does not identify which covariates were included, how they were modeled, or the exact adjustment procedure. The reported pairwise estimates therefore should be described as ANCOVA results without making assumptions about the adjustment details.

The pairwise estimates are presented as mean differences in final values, each with a 95% confidence interval and a p-value. A confidence interval for a difference expresses uncertainty about the contrast itself. When such an interval includes zero, the posted data do not rule out no difference under the analysis assumptions. When it excludes zero, the interval is inconsistent with a zero contrast at the corresponding confidence level under those assumptions. This is not a measure of clinical importance. The registry record does not give a minimum clinically important difference for FMD.

General statistical point: a p-value measures how incompatible the observed data are with a specified null model, assuming that model and the analysis assumptions are appropriate. It is not the probability that the null hypothesis is true, and it does not measure the size or importance of an effect. The registry lists p = 0.045 and p = 0.014 for two contrasts, and larger values for the other four. Because the record does not report a multiplicity procedure, these values should be read as the posted comparison-specific p-values rather than as results known to account for the set of comparisons.

There are six pairwise comparisons among the four combinations in the posted primary outcome analyses. Looking across several contrasts raises a general multiplicity concern: when many hypotheses are tested, the chance of at least one small p-value can increase if the tests are treated as independent opportunities for a finding. The tests may be related because they share groups, but the record does not report a method for handling that dependence or the multiple-testing issue. It also does not state which comparisons, if any, were prespecified as the main contrasts.

The outcome summaries include different numbers of participants by arm, and the registry says the primary analysis includes only individuals with both pre- and post-intervention data. General statistical point: restricting an analysis to participants with complete measurements can affect representativeness if the availability of data is related to outcome or group assignment. The record does not report reasons for missing measurements, imputation methods, or sensitivity analyses. It is therefore not possible to assess from the registry record whether the analyzed participants differ systematically from those without paired measurements.

The record also describes a sample-size planning illustration based on the observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Such an illustration is a planning calculation, not observed power and not evidence that the trial was designed around those assumptions. The trial’s own sample-size justification and any interim analyses are not reported in the registry record. General statistical point: over-dispersion is a concern when the variability in data exceeds what a model assumes; it can make standard errors too small if not handled appropriately. The posted primary outcome is summarized as a continuous measure, and the registry does not report an over-dispersion assessment or model diagnostics.

The registry lists 36 analyses across the outcome record, but does not explain how that count relates to the prespecified analysis plan. The record does not report whether outcome analyses were blinded to group assignment, how covariates were selected, or how departures from modeling assumptions were evaluated. Those omissions limit what can be inferred about the robustness and prespecification of the statistical results.

10. Analyses Reported by the Sponsor

The registry’s reported inferential comparisons use ANCOVA and are described as mean differences in final values. The arm-level values, in contrast, are means of change scores with confidence intervals. These summaries are not interchangeable: an adjusted comparison of final values need not equal a simple difference between the posted change means. The record does not describe the ANCOVA covariates or adjustment details, so the reported estimates should be interpreted using the method named in the registry rather than reconstructed from the arm summaries.

The registry record does not identify a discrepancy between the sponsor’s analysis and a recalculation. It does not give a separate recalculated pairwise estimate in the reported results. If a simple unadjusted recalculation is considered, it is a different calculation from the sponsor-reported ANCOVA and should not replace that analysis. The ANCOVA estimates and their confidence intervals and p-values remain the registry’s reported inferential results. The record does not provide enough methodological detail to reproduce those adjusted analyses independently.

11. Multiplicity, Missing Data and Analysis Populations

The primary outcome is accompanied by six reported pairwise comparisons among the four treatment combinations. The registry record does not report a family-wise error procedure, a false-discovery procedure, or another adjustment for multiple comparisons. It also does not identify a single primary pairwise contrast or explain whether the six comparisons were prespecified. Accordingly, the reported p-values are best read as the individual values attached to the posted ANCOVA comparisons; the record does not establish that they account for the full set of tests.

The record lists six outcome measures, including the primary FMD measure and five posted secondary outcomes. It also lists 36 analyses, but does not explain the analysis count or specify how testing across outcomes and comparisons was managed. No hierarchy of outcomes, gatekeeping strategy, or other multiplicity plan is reported in the registry record. This absence does not prove that no such plan existed; it means the record does not provide it.

For the primary endpoint, the stated analysis population includes only individuals with both pre- and post-intervention data. The number of participants attached to the four arm-level summaries is 12, 11, 16, and 9, respectively. The record does not explain why other enrolled participants are absent from those outcome summaries, whether measurements were missing for other reasons, or whether the analysis included all randomized participants in any other form. Reasons for missingness, imputation, and sensitivity analyses are not reported in the registry record.

These details matter because complete-measurement analyses can be affected when the chance of having both measurements is related to group assignment or to the outcome. The registry does not provide enough information to assess that possibility. It also does not describe the handling of protocol deviations, analysis population definitions beyond the paired-measurement statement, or interim analyses. The extent to which missing data and multiple testing could influence interpretation therefore remains uncertain.

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 non-serious adverse event terms

The registry lists no serious adverse events in any of the four groups and no deaths. For serious events, the listed numbers at risk were 22 for low-intensity exercise with placebo, 21 for high-intensity exercise with placebo, 24 for low-intensity exercise with metformin, and 24 for high-intensity exercise with metformin. These are the counts associated with the safety summaries and are not the same as the primary outcome analysis counts.

For other adverse events, the registry lists zero affected participants in the first three groups and one in the high-intensity exercise with metformin group. The corresponding numbers at risk are 22, 21, 24, and 24. No serious adverse-event terms are listed. These figures describe what the registry records; they do not establish that no events occurred outside the recorded categories or observation period. The registry record does not provide additional detail about event definitions, severity grading for other events, follow-up completeness, or the length of safety observation. With small group counts, a recorded zero should be read as no reported event in that group, not proof that an event could not occur.

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

The posted results describe changes in fasting brachial artery FMD among the participants with both pre- and post-intervention measurements, along with ANCOVA comparisons of final values across the four exercise-and-medication combinations. The arm means and reported pairwise estimates give information about the direction and size of the observed differences, while their confidence intervals convey uncertainty. The results are not equally precise across all contrasts, and several pairwise intervals include zero.

The registry reports two comparisons with confidence intervals excluding zero: low-intensity exercise with placebo versus low-intensity exercise with metformin, and low-intensity exercise with placebo versus high-intensity exercise with metformin. The other four reported intervals include zero. These are results of the posted analyses, not proof that a combination is beneficial or ineffective. The record does not give a clinical-importance threshold, a multiplicity adjustment, or enough detail to determine how robust the estimates are to missing measurements and model choices.

The primary endpoint is a vascular function measure, not a direct measure of cardiovascular events or future disease. The registry’s secondary outcomes include insulin sensitivity and forearm microvascular measures, but the results for those outcomes are not described in the record information used for this interpretation. The study summary states broader aims concerning blood flow and insulin action; aims should not be confused with demonstrated findings.

The trial’s randomized design supports comparisons between assigned groups in principle, but interpreting those comparisons still depends on adequate conduct, analysis, measurement, and complete reporting. Details on the randomization process, covariate adjustment, missing-data handling, and multiplicity are not reported in the registry record. The findings therefore should be read as estimates for the measured endpoint in the analyzed participants, with uncertainty, rather than as a definitive answer about vascular health or clinical outcomes.

14. Why This Trial Matters Statistically

This trial is statistically interesting because it compares combinations of two components: exercise intensity and medication assignment. Its four-arm structure makes it possible to examine contrasts that change one component while holding the other fixed, as well as contrasts in which both components differ. Such comparisons can be informative, but the interpretation depends on which contrasts were planned and how they were analyzed. The registry reports pairwise ANCOVA estimates but does not identify a prespecified contrast hierarchy or the covariates used.

The endpoint also illustrates the distinction between an outcome’s measurement and its clinical meaning. FMD is recorded as a percentage change in artery diameter and summarized as a continuous measure. The registry states that higher values and positive change indicate a better endpoint value, but it does not state how large a difference would be important to patients or clinical practice. Statistical uncertainty and clinical importance are separate questions.

The record offers an opportunity to read effect estimates alongside their confidence intervals rather than focusing only on p-values. The estimates vary in precision, and some intervals include zero while others do not. At the same time, six pairwise comparisons and multiple outcomes raise questions about multiplicity, and the available record does not say how those questions were handled. The complete-measurement analysis also makes missing-data reporting consequential.

Finally, the registry makes clear that the primary result concerns an intermediate vascular measure at week 16. The listed aims extend to blood flow and insulin action, but those aims are not substitutes for posted outcome results. The case underscores why statistical interpretation should distinguish design, endpoint, analysis population, effect estimate, uncertainty, and clinical relevance.

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.

Several trial-specific details needed for a fuller appraisal are not reported in the registry record. The primary analysis is limited to individuals with both baseline and week 16 data, but the record does not state why other participants lack paired measurements or how missing data were handled. The arm-level analysis counts vary, and the safety counts are different; the record does not explain the relationship among these analysis populations.

The record names ANCOVA for the pairwise primary outcome comparisons but does not describe the covariates, model specification, or diagnostic checks. It does not state the subtraction order for the reported mean differences in final values, which makes interpretation of the signs less direct. The arm summaries are changes from baseline, while the inferential comparisons are described as final-value differences; these are distinct quantities.

Multiplicity is another limitation. Six pairwise analyses are reported, alongside multiple outcomes and a total of 36 analyses, but the testing strategy and prespecified contrast plan are not reported. The registry also does not give a threshold for clinically meaningful FMD change. The sample-size justification, interim analysis plan, and details of randomization and masking procedures are not reported in the registry record.

The safety summary lists no serious adverse events and one other adverse event in one group, but offers limited context about event definitions, ascertainment, and observation duration. Finally, the primary endpoint is a vascular function measure at week 16; it does not itself report cardiovascular events. These limitations do not negate the posted estimates, but they restrict the conclusions that can be drawn from the registry record alone.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Exercise Dose and Metformin for Vascular Health in Metabolic Syndrome — NCT03355469.
• Registry record last updated 2025-09-22; status last verified 2025-09.
• Results first posted 2025-09-22.
• 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.

19. Record Summary

NCT03355469 is a completed randomized, parallel-group trial sponsored by Rutgers University, listed as phase 2 and phase 3, with 91 participants enrolled. It studied low- and high-intensity exercise combined with metformin or placebo in adults with metabolic syndrome, with quadruple masking reported.

The primary outcome was change in fasting, unscaled brachial artery FMD from week 0 to week 16. The registry reports arm-level mean changes and 95% confidence intervals, plus six pairwise ANCOVA analyses of mean differences in final values. The analysis population for the primary outcome included only participants with both pre- and post-intervention data.

Five secondary outcomes are posted, covering insulin sensitivity, augmentation index, and forearm microvascular measures. The registry lists no serious adverse events or deaths and one other adverse event in the high-intensity exercise with metformin group. Details of the analysis plan, multiplicity handling, missing-data methods, and sample-size justification are not reported in the registry record.