Metformin and Muscle in Insulin-resistant Older Veterans: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Metformin and Muscle in Insulin-resistant Older Veterans (NCT01804049), a randomized phase 1, phase 2 study. The primary outcome is Change in Total Lean Mass From Baseline.

2. Clinical Question

3. Trial Design

The registry classifies this completed study as randomized, double-masked, and parallel, with Phase 1 and Phase 2 listed. Its recorded enrollment is 120. The condition listed is prediabetes, and the sponsor is the VA Office of Research and Development. The start date is 2014-04-08, and the primary completion date is 2018-08-31.

The record describes 60 participants assigned to placebo and 60 enrolled participants assigned to metformin. It also describes a simple adaptive randomization scheme intended to balance gender, age, and BMI, with allocation probabilities of 64% to 36%. The record does not explain how those probabilities relate to the arm descriptions, so the relationship between these design statements is not reported in the registry record. They should not be treated as interchangeable descriptions of actual treatment-group counts.

Participants were to be followed for up to 3 years, with walk time and lean mass measured annually. The primary outcome description says whole body DXA scans were performed at baseline and at 1, 2, and 3 year follow-up visits. The listed secondary outcomes are change in 400 meter walk speed and change in muscle characteristics. The record identifies 3 outcome measures and 3 analyses, but does not describe the full analysis plan or provide a single primary-outcome contrast.

The registry record gives the trial status as completed. Completion and a listed outcome do not, by themselves, establish that the planned comparison is available or interpretable. In particular, the record does not report a primary treatment-effect estimate, confidence interval, or test result in a form that reduces the outcome to one comparison.

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: Of the 431 assessed for eligibility, 120 met inclusion criteria and were randomized to treatment.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: A simple adaptive randomization scheme was developed to balance gender, age and BMI. 120 subjects were randomized to treatment conditions according to 64% to 36% allocation probabilities. Subjects were followed for up to 3 years, with walk time and lean mass measured annually. The study experienced roughly 38% loss-to-follow up at year 3.

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 Total Lean Mass From Baseline, measured over 3 years.

The primary endpoint is change in total lean mass from baseline, with a stated timeframe of 3 years and a unit of grams lean mass. The outcome description says participants had whole body dual x-ray absorptiometry scans using a Hologic QDR 4500W DXA scanner, performed by a certified DXA operator. The description says the scans were used to determine total body lean mass and appendicular lean mass (Kg), and that changes were calculated from baseline to the three year data point.

As general context, lean mass is a body-composition measure. It is relevant to this study because the registry frames age-related loss of muscle mass, strength, and function as the clinical concern. A measured change in lean mass can describe one aspect of muscle-related change, but it is not itself a measure of strength, physical function, falls, or fractures. The registry lists 400 meter walk speed and muscle characteristics as secondary outcomes, rather than the primary endpoint.

The record says that when a participant withdrew before collection of 3 year data, the final available time point was used. It does not report how many participants had each follow-up measurement or how the endpoint was summarized across groups. Although the primary outcome is labeled as a geometric mean with standard deviation as dispersion, no corresponding primary result estimate is reported. The listed unit in the endpoint is grams lean mass, while the description refers to lean mass in Kg; the registry record does not explain this difference.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies a randomized, double-masked, parallel-group study. In general, randomization is intended to make treatment groups comparable with respect to factors that could affect an outcome, while masking is intended to limit the influence of treatment knowledge on participants or study conduct. The record does not specify who was masked, how allocation was implemented, or whether masking was maintained. The design label alone does not reveal the success of those procedures.

What does the primary endpoint describe?

The primary endpoint is change in total lean mass from baseline, with the timeframe stated as 3 years. DXA scans were described at baseline and at 1, 2, and 3 year follow-up visits. The endpoint description says changes in appendicular and total lean mass were calculated from baseline to the three year data point. It also says that if a participant withdrew before collection of 3 year data, the final time point available was used. The record labels the primary parameter as a geometric mean and the dispersion as standard deviation, but does not provide an endpoint estimate or explain in detail how the geometric-mean summary was applied to change scores.

As general statistical context, an estimate summarizes the observed data under a specified analysis. A confidence interval describes uncertainty around an estimate under the assumptions of that analysis; it is not a guarantee that the true value lies within the interval. A p-value, when reported, describes how compatible the data are with a specified null model and does not measure clinical importance. None of these primary-comparison statistics is reported in the registry record. The endpoint label and measurement plan cannot be used to reconstruct them.

What does the record say about group allocation?

The record describes 60 participants assigned to placebo and 60 enrolled participants assigned to metformin. It also says a simple adaptive randomization scheme was developed to balance gender, age, and BMI, and gives allocation probabilities of 64% to 36%. These statements do not explain how the stated probabilities correspond to the equal group descriptions. The registry record does not report enough detail to resolve that relationship. Further, the at-risk counts in the adverse-event record are not the same kind of information as the arm descriptions: they are reported alongside event counts and should not be interpreted as randomized group sizes.

In general, an adaptive allocation approach can use characteristics or accumulated assignments to guide subsequent assignments. The record’s description says the aim was balance on gender, age, and BMI, but it does not specify the algorithm, implementation details, or whether balance was achieved. No inference about achieved balance should be made without the relevant baseline or allocation results.

How should the planning calculations be read?

The registry's stated sample-size framework describes a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. The effect to detect is described as a stated fraction of the observed effect. For a general interpretation, these are hypothetical design calculations: they illustrate participant requirements under assumptions about an effect and analysis, rather than measuring the probability that the completed trial found an effect. They are not observed power. The registry record does not report a detailed sample-size justification or provide the assumptions needed to independently assess a planned target.

The framework says that time-to-event calculations give a total number of events, while other calculations give participants per arm for 80% power. Any planning display should be understood according to that stated distinction, not as a count of observed participants or events. Because no planning values are stated in the registry entries described for this analysis, no particular planning requirement can be quoted. The record also does not explain which assumed effect fractions or endpoint variances were used beyond the general framework.

Why does a single comparison matter?

A treatment comparison is ordinarily stated as an estimate of the outcome contrast between assigned groups, accompanied by a measure of uncertainty and, where appropriate, a test result. A primary outcome measured at several time points or represented by several categories may require a prespecified way to reduce or model those data. In general, the selected approach affects what the resulting estimate means. Here, the registry specifically notes that the primary outcome has several categories or time points and is not reduced to one comparison. No comparison method or primary estimate is reported, so the intended contrast and its precision cannot be evaluated from the registry record.

The record identifies 3 outcome measures and 3 analyses. That count does not establish how analyses were selected, whether they were prespecified, or how the results were interpreted. It does not report a statistical model, covariate adjustment, confidence-interval method, or handling of multiple testing. These methods are not reported in the registry record.

What are the limits of the available methods information?

In general, missing follow-up data can affect an analysis if the participants with observed measurements differ from those without them. The record's use of the final available follow-up point for participants without a 3 year measurement is one stated feature of the endpoint description; it is not a complete account of missing-data methods. The record does not describe other imputation procedures, sensitivity analyses, or assumptions about missing observations. It also does not specify the analysis population, such as whether results were based on all randomized participants or another group. Without those details and a reported treatment contrast, the robustness of a primary analysis cannot be assessed.

10. Multiplicity, Missing Data and Analysis Populations

The registry identifies 3 outcome measures and 3 analyses. It lists change in total lean mass as the primary outcome and names change in 400 meter walk speed and change in muscle characteristics as secondary outcomes. The primary outcome is described across several categories or time points, and the record says it is not reduced to one comparison. The number of outcomes and analyses does not reveal whether a hierarchy, adjustment, or other multiplicity strategy was used. Such a strategy is not reported in the registry record.

As general context, when multiple outcomes or repeated measurements are examined, the chance of at least one apparently unusual result can depend on how many comparisons are made and how they are selected. A prespecified approach can clarify which comparison is primary and how additional analyses should be interpreted. No prespecified testing hierarchy or adjustment for multiple comparisons is reported. Since no single primary estimate or inferential result is posted, it is not possible to determine how multiplicity was handled in practice.

For missing data, the endpoint description says that participants who withdrew before collection of 3 year data had their final available time point used. It does not report the number or timing of withdrawals, missing measurements by group, or whether other missing-data methods were applied. The record does not state the analysis population or report sensitivity analyses addressing missing outcomes. These omissions limit assessment of how representative the analyzed measurements were of the randomized groups and how dependent results might be on follow-up availability.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: fall requiring hospitalization (11.6%), prostatectomy (6.5%), chest pain (5.2%), kidney or bladder cancer (4.7%), upper respiratory infection (3.9%).

The registry lists serious adverse events for participants at risk in each group. For placebo, 43 participants were at risk and 25 were affected; for metformin, 77 were at risk and 52 were affected. For other adverse events, the listed figures are 43 at risk and 24 affected in the placebo group, and 77 at risk and 52 affected in the metformin group. Deaths are listed as 0 for placebo and 1 for metformin. These figures are reported as group counts; they are not a comparative analysis adjusted for follow-up or exposure.

The registry also lists the most frequent serious event terms with percentages: fall requiring hospitalization, 11.6%; prostatectomy, 6.5%; chest pain, 5.2%; kidney or bladder cancer, 4.7%; upper respiratory infection, 3.9%; and stroke/TIA, 2.6%. These listed percentages do not establish that the events were caused by treatment. The record does not state the denominator for these percentages in the registry record, nor whether one participant could contribute more than one event term. Counts across terms should not be added.

In general, adverse-event counts describe events recorded during a study, while causal attribution requires further clinical and analytic assessment. The registry record does not report event timing, duration of exposure, severity beyond the serious-event classification, or a causal assessment for the listed events.

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

The record establishes that a completed randomized, double-masked, parallel trial compared metformin with placebo in older adults with prediabetes, and that change in total lean mass was designated as the primary outcome. It also describes DXA-based measurements and follow-up through a stated 3 years. These details help define the question the trial was designed to address.

They do not establish the result of the primary comparison. The registry record does not reduce the primary outcome's several categories or time points to one comparison, and no primary treatment-effect estimate, confidence interval, or p-value is reported. Therefore, neither the size nor direction of a group difference, nor its statistical precision, can be described from this record. The absence of a posted comparison is not evidence that the groups were the same, and it is not evidence that they differed.

The listed secondary outcomes indicate that walking speed and muscle characteristics were also considered. Their names alone do not show whether either outcome changed or whether groups differed. Similarly, the serious and other adverse-event figures are descriptive counts and do not show that an event was caused by metformin or placebo. The record does not report a comparative safety analysis or enough detail to account for exposure and event timing.

As general statistical context, a treatment-effect estimate is most informative when it is paired with an uncertainty interval and a clearly defined analysis. A result can be statistically uncertain even if its point estimate is not zero, and a statistically detectable difference does not by itself establish clinical importance. In this case, the registry record does not contain the primary comparison needed to make either assessment.

The completed status indicates that the trial is recorded as completed; it should not be read as a statement that results for every planned analysis are posted. The appropriate interpretation is limited to the study design, outcome definitions, follow-up description, and safety counts that the record reports. Broader claims about benefit, lack of benefit, or clinical use are not supported by the reported primary-outcome information.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of why a defined endpoint and a reported treatment contrast are both necessary for interpreting randomized evidence. The registry identifies a primary outcome, its measurement approach, and a follow-up timeframe. Those elements make the intended measurement more concrete, but the record also says that the primary outcome spans several categories or time points and is not reduced to one comparison. Without a clearly reported contrast, readers cannot determine the estimated group difference or its uncertainty.

The record also illustrates the importance of distinguishing design descriptions from observed analysis denominators. It describes equal group assignments while also reporting allocation probabilities of 64% to 36%; the registry does not explain how these statements relate. Separately, adverse-event at-risk counts are reported as 43 and 77. These quantities refer to different aspects of the record and should not be treated as interchangeable measures of randomized group size. Clear accounting of allocation, follow-up, and analysis populations is essential for evaluating which participants contribute to each result.

The missing outcome comparison also shows why completion status alone is not a statistical result. A trial can have a completed status and a detailed endpoint definition without a posted primary estimate, confidence interval, or test result. In that situation, no claim about the size, direction, or precision of the main treatment contrast can be made from the registry record.

Finally, the study description includes repeated measurement and a stated approach to participants without a 3 year measurement, while leaving other missing-data and multiplicity methods unreported. In general, such choices influence the interpretation and reliability of estimates. The record's limits make transparent reporting of the selected analysis, included population, and uncertainty especially important for readers assessing the trial statistically.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The main limitation of the registry record for interpretation is that it does not report a single primary comparison. It identifies change in total lean mass from baseline as the primary outcome and says the outcome has several categories or time points, but does not reduce those data to one treatment contrast. No primary estimate, confidence interval, or p-value is reported, so effect magnitude, direction, and precision are unavailable.

The endpoint description contains details that are not reconciled. The primary outcome unit is stated as grams lean mass, while the measurement description refers to lean mass in Kg. The record does not explain the difference. It also labels the parameter as a geometric mean and dispersion as standard deviation without reporting the corresponding results or clarifying the summary method for change. These details limit assessment of how the endpoint was calculated and presented.

There are also unresolved design and denominator details. The arm descriptions state 60 participants for each group, while the randomization description gives allocation probabilities of 64% to 36%. The record does not explain their relationship. The adverse-event record gives at-risk counts that differ from the arm descriptions, but does not explain the flow from assignment to the safety populations. The analysis population and participant flow are not reported in the registry record.

Follow-up is described through 3 years, with the final available measurement used for participants who withdrew before the 3 year data collection. The number of missing measurements, timing of withdrawal, and other missing-data procedures are not reported. The statistical model, multiplicity strategy, and analysis details are also not reported. These gaps prevent assessment of whether the primary result would be sensitive to follow-up availability or analysis choices.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Metformin and Muscle in Insulin-resistant Older Veterans — NCT01804049.
• Registry record last updated 2020-02-11; status last verified 2020-02.
• Results first posted 2020-02-11.
• 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

The registry record describes a completed randomized, double-masked, parallel Phase 1 and Phase 2 study sponsored by the VA Office of Research and Development. It lists 120 enrolled participants with prediabetes and compares metformin with placebo. The recorded start date is 2014-04-08, and the primary completion date is 2018-08-31.

The primary outcome is change in total lean mass from baseline over a stated 3 years, assessed using DXA. Secondary outcomes are change in 400 meter walk speed and change in muscle characteristics. The endpoint description states that the final available time point was used for participants who withdrew before the 3 year data collection.

The registry does not reduce the primary outcome to one comparison and does not report a single primary treatment-effect estimate or its precision. It lists serious and other adverse-event counts and deaths by group, but these are descriptive figures and do not establish causation. Further details about the analysis population, missing-data methods, and multiplicity are not reported in the registry record.