This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for A Trial of Magnesium Dependent Tinnitus (NCT01273883), a randomized phase 3 study. The primary outcome is Tinnitus Distress Rating.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01273883 |
| Phase | Phase 3 |
| Condition | Tinnitus |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | Double |
| Enrollment | 38 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Mayo Clinic |
| Results posted | Yes |
2. Clinical Question
Population
Adults or other specific eligibility groups are not identified in the registry summary. The record describes 38 enrolled subjects with tinnitus; it does not report that all subjects completed the distress rating scale.
Intervention
Magnesium was given at 532 mg daily for 25 days. One sequence received magnesium first, followed by a 2-week washout and then placebo for 25 days.
Comparator
Placebo was given daily for 25 days. The other sequence received placebo first, followed by a 2-week washout and then magnesium at 532 mg daily for 25 days.
Primary question
The trial's stated purpose was to examine potential benefit in lessening tinnitus severity. Its primary outcome was a patient-reported Tinnitus Distress Rating, but comparative outcome results are not reported in the registry record.
The practical question is whether participants' reported tinnitus distress differed between their magnesium and placebo periods. Because this was a crossover design, each participant could receive both treatments in a randomized order, rather than being assigned to only one treatment for the entire study. This design can support a within-participant comparison, but the registry record does not report the analysis used to make that comparison.
The distress rating was a single-item scale ranging from 0, meaning no tinnitus, to 10, meaning the worst possible tinnitus. The primary outcome description identifies assessment before and after treatment, with a timeframe of up to four weeks. It also states that not all subjects completed the rating scale. The registry lists comparisons of average Tinnitus Handicap Inventory scores as secondary outcomes across all subjects, all men, and all women. The record names four outcome measures overall, but it does not provide numerical results for these outcomes.
Accordingly, the clinical question can be described, but the posted registry information does not establish the direction or size of any difference in distress or handicap scores. No conclusion about an effect can be drawn from the treatment schedule or trial title alone.
3. Trial Design
The registry describes a randomized, double-blind, Phase III crossover trial sponsored by Mayo Clinic. The condition listed is tinnitus, and enrollment was 38. The study is marked completed. Its recorded start was 2011-07, and primary completion was 2013-10.
Participants were assigned to one of two treatment sequences. In the first, magnesium at 532 mg daily was taken for 25 days, then participants had a 2-week washout, followed by 25 days of placebo. In the second, placebo was taken daily for 25 days, followed by the same stated washout, then magnesium at 532 mg daily for 25 days. Thus, both sequences included exposure to magnesium and placebo, but in a different order.
In a crossover trial, the participant can serve as their own comparator, because measurements under one treatment period may be compared with measurements under another period for the same person. This can reduce the influence of stable differences between participants. It also means that order and timing may matter: a treatment-period comparison can be affected by changes over time, incomplete follow-up, or lingering effects from an earlier period. These are general design considerations, not findings about this trial. The registry record does not report how those issues were addressed analytically or whether any carryover assessment was planned.
The record identifies double masking but does not specify which individuals were masked. Details such as the randomization procedure, allocation concealment, eligibility criteria, recruitment setting, or adherence assessment are not reported in the registry record. Nor does the record describe the reason for selecting the washout duration or the treatment-period length. The Phase III label is a design classification; it is not itself evidence about the outcomes. Numerical primary and secondary outcome analyses are not reported in the registry record.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
First Intervention
| Stage | Magnesium First, Then Placebo | Placebo First, Then Magnesium |
|---|---|---|
| STARTED | 19 | 19 |
| COMPLETED | 17 | 18 |
| NOT COMPLETED | 2 | 1 |
Reasons for not completing this period:
| Reason | Magnesium First, Then Placebo | Placebo First, Then Magnesium |
|---|---|---|
| Adverse Event | 2 | 1 |
Washout Period of 2 Weeks
| Stage | Magnesium First, Then Placebo | Placebo First, Then Magnesium |
|---|---|---|
| STARTED | 17 | 18 |
| COMPLETED | 17 | 18 |
| NOT COMPLETED | 0 | 0 |
Second Intervention
| Stage | Magnesium First, Then Placebo | Placebo First, Then Magnesium |
|---|---|---|
| STARTED | 17 | 18 |
| COMPLETED | 15 | 17 |
| NOT COMPLETED | 2 | 1 |
Reasons for not completing this period:
| Reason | Magnesium First, Then Placebo | Placebo First, Then Magnesium |
|---|---|---|
| Lost to Follow-up | 1 | 1 |
| Lack of Efficacy | 1 | 0 |
Analysis population for the primary outcome, as defined in the registry: Not all subjects completed the distress rating scale.
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | Entire Study Population |
|---|---|---|
| Participants analysed | 38 | |
| Age, Continuous | years | 61.45 (SD 11.58) |
| Sex: Female, Male: Female | Participants | 13 |
| Sex: Female, Male: Male | Participants | 25 |
| Region of Enrollment: United States | participants | 38 |
6. Primary Endpoint
The registry lists the primary outcome as Tinnitus Distress Rating, measured over Pre-treatment, Post-treatment, up to four weeks.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | units on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is the Tinnitus Distress Rating, described as a single-item patient-reported measure of how distressing tinnitus is. The scale ranges from 0, meaning no tinnitus, to 10, meaning the worst possible tinnitus. This kind of rating asks participants to report their own experience directly, rather than using an observer's rating as a substitute for the person's perceived distress.
The endpoint is recorded as a mean with standard deviation, and its stated timeframe is pre-treatment and post-treatment, up to four weeks. A mean describes the average rating in a group or treatment period. A standard deviation describes how spread out individual ratings are around that average; it is not the uncertainty of the estimated mean. A mean difference between treatment periods could be useful for expressing the average contrast, but the registry record does not report such a contrast or any associated uncertainty.
A brief single-item measure can capture a focused patient-reported experience, though it cannot describe every dimension of tinnitus. The record separately lists Tinnitus Handicap Inventory outcomes as secondary outcomes, including comparisons across all subjects and separately across men and women. The registry does not report numerical results for either the distress rating or the handicap outcomes. It also notes that not all subjects completed the distress scale, so the number contributing to any endpoint analysis and the handling of missing ratings are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The central interpretive limitation is that the registry record contains no reported analyses for the outcomes. It identifies a primary patient-reported measure and describes how treatment was scheduled, but it does not give the observed mean ratings, a treatment contrast, a confidence interval, a test statistic, or a p-value. The direction, magnitude, and precision of the primary outcome comparison therefore cannot be assessed from this record.
The primary endpoint was designed to capture tinnitus distress on a 0-10 scale, with a stated assessment before and after treatment and a timeframe of up to four weeks. The record says that not all subjects completed the scale. Without the number of usable observations for each period, it is not possible to determine how much outcome information contributed to an analysis or whether missingness differed by sequence or treatment period. The registry does not report an analysis population or a missing-data method.
There are also no numerical results reported for the listed secondary Tinnitus Handicap Inventory outcomes. Those outcomes are described for all subjects and for men and women separately, but subgroup labels do not provide evidence of a difference. No estimates or uncertainty measures are available for these comparisons.
The trial's crossover structure is relevant to interpretation. A within-participant contrast can account for stable characteristics shared across a participant's treatment periods, but sound interpretation still depends on how period, sequence, and possible carryover effects are handled. The registry record does not report those analysis details. It is therefore not possible to know whether a reported comparison, if one existed elsewhere, would be adjusted for the design features or based on a simpler summary.
The adverse-event figures are descriptive counts: no serious adverse events were recorded as affecting participants in either treatment group, while other adverse events affected 7 participants in the magnesium group and 3 in the placebo group. Death counts are not reported in the registry record. These figures do not supply the missing primary efficacy analysis and should not be read as a comparison of treatment benefit. The registry's completed status indicates the study's status, not that numerical outcome findings are present.
Overall, the posted registry information permits description of the planned treatment sequence, enrolled number, endpoints, and recorded adverse-event counts. It does not permit a quantitative estimate of the primary treatment contrast or a judgment about how precisely that contrast was measured.
9. Statistical Methods Explained
The registry identifies the primary outcome as a continuous measure summarized by a mean and standard deviation. General statistical interpretation begins by distinguishing the observed value from its uncertainty. A mean is a group-level average, while the standard deviation describes variation among individual observations. Neither alone indicates how precisely a treatment comparison has been estimated. Precision for a comparison is commonly conveyed with a confidence interval, but no interval for the primary endpoint is reported in the registry record.
What would a treatment contrast represent?
For this crossover study, the clinically relevant statistical contrast would ordinarily compare a participant's distress ratings during the magnesium and placebo periods, while respecting the randomized treatment order and the timing of the measurements. A treatment contrast is an estimate of the average difference associated with the two treatment conditions in the analyzed participants. Its interpretation depends on how the outcome was defined and which observations were included. The record supplies no such estimate, so neither its sign nor its size is known from the registry.
General statistical practice distinguishes a point estimate from a confidence interval. The point estimate gives the estimated contrast; the interval describes a range of values compatible with the data and the assumptions of the analysis. A narrow interval indicates greater precision than a broad interval, but an interval's interpretation also depends on the design and method. A p-value addresses compatibility of the observed data with a specified null model; it does not measure the size or clinical importance of an effect. No confidence interval or p-value for the primary comparison is reported in the registry record.
Why does crossover structure matter?
In a crossover design, treatment comparisons are made across periods in which the same participant may receive each treatment. Because measurements from one participant are related, a general analysis would account for that pairing rather than treating all observations as independent. A paired comparison can remove some between-person variation that would otherwise obscure a treatment contrast. This does not automatically eliminate bias or guarantee precision: period effects, changes over time, missing period measurements, and treatment carryover can matter.
Carryover refers, in general, to an effect of an earlier treatment that persists into a later period. A washout period is intended to separate treatment periods, but its presence alone does not show that carryover was absent. The registry describes a 2-week washout but does not report the analysis strategy for period or sequence effects, whether carryover was assessed, or how any such assessment would affect interpretation. These details are not reported in the registry record.
What does the reported dispersion mean?
The endpoint is specified as a mean with standard deviation. The standard deviation summarizes person-to-person spread in ratings; it is not the standard error and is not a confidence interval. A standard error describes uncertainty in an estimate, while an interval uses an uncertainty estimate to express precision. In a crossover analysis, the variability of within-person differences may be more directly relevant to the treatment contrast than the separate standard deviations for each treatment period. The registry does not report the required outcome summaries or a within-participant analysis.
What can sample-size illustrations establish?
The registry's sample-size assumptions describe a planning illustration based on an observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The assumed effect to detect is described as a stated fraction of the observed effect. Such a calculation is a planning illustration, not an analysis of observed trial outcomes and not observed power. It cannot show that the trial achieved a particular power after completion. The registry does not report a sample-size justification for the original trial, and the observed effect and resulting planning counts are not reported in the registry record.
Sample-size calculations depend on assumptions about the outcome, variability, effect size, allocation, and analysis. If assumptions do not match the trial's actual design or data, a planning result may not describe the precision ultimately achieved. In particular, a generic equal-allocation, normal-approximation description does not by itself explain how a crossover comparison would account for within-participant pairing, treatment sequence, or period. Those design-specific details are not reported in the registry record.
What role do analysis counts play?
The registry lists 0 analyses. This means there are no registered numerical analysis results to interpret in the record, not that the trial found no effect or that an estimated effect was exactly zero. The primary outcome is also described as having several categories or time points and is not reduced to one comparison in the posted results. Without a specified comparison and its estimate, an inferential interpretation cannot be reconstructed from the description alone.
General statistical concepts can clarify how the intended data might be analyzed, but they cannot replace the missing analysis record. There is no basis to infer a test, model, adjustment, confidence interval, or significance finding for this trial. Any quantitative claim about the primary endpoint would require outcome data and analysis results that are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists four outcome measures overall and identifies Tinnitus Distress Rating as the primary outcome. Its listed secondary outcomes compare average Tinnitus Handicap Inventory scores across all subjects, all men, and all women. The record does not give numerical results for those outcomes. It also does not report whether hypotheses or endpoints were prioritized beyond the primary/secondary labels, or whether any adjustment for multiple comparisons was planned.
Multiplicity is a general concern when several outcomes, subgroups, time points, or treatment contrasts are examined. Considering many comparisons can increase the chance of a seemingly notable result arising by chance if each is interpreted separately. Whether and how this applies to the trial's analyses cannot be determined without an analysis plan and reported results. The registry record does not report an adjustment strategy or interim analyses.
The primary outcome description states that not all subjects completed the distress rating scale. The number with ratings, the reasons for missingness, and whether missingness occurred before or after treatment are not reported in the registry record. Neither the analysis population nor the method used to handle missing observations is reported. In general, complete-case analysis, imputation, and models using available repeated measurements rely on different assumptions; none can be attributed to this study from the registry information.
For a crossover study, missing data can be consequential if a participant has a rating for one treatment period but not the other, because the within-participant comparison may be unavailable or handled differently. The record does not state how incomplete sequences were analyzed. The outcome entry also notes multiple categories or time points and is not reduced to a single comparison in the posted results, so a unified primary estimate cannot be identified.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Magnesium | 0 | 38 | 0.0% |
| Placebo | 0 | 38 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Magnesium | 7 of 38 |
| Placebo | 3 of 38 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Magnesium | Placebo |
|---|---|---|---|
| Loose Stool | Gastrointestinal disorders | 3 of 38 | 1 of 38 |
| Diarrhea | Gastrointestinal disorders | 3 of 38 | 0 of 38 |
| Emergency Room Visit | General disorders | 1 of 38 | 1 of 38 |
| Pleurisy | Respiratory, thoracic and mediastinal disorders | 0 of 38 | 1 of 38 |
| Headache | General disorders | 1 of 38 | 0 of 38 |
| Elevated Blood Pressure | Blood and lymphatic system disorders | 0 of 38 | 1 of 38 |
| Lower Abdominal Discomfort | Gastrointestinal disorders | 0 of 38 | 1 of 38 |
| Intermittent Ankle Swelling | Blood and lymphatic system disorders | 1 of 38 | 0 of 38 |
The registry lists 38 participants at risk for serious adverse events in the magnesium group and 38 in the placebo group. It records 0 participants affected by serious adverse events in each group. The serious-event terms list is empty. These are the registry's recorded counts; they do not establish that every possible event was absent or that the treatments have equal safety.
For other adverse events, the record lists 38 at risk in each group, with 7 affected in the magnesium group and 3 affected in the placebo group. These are counts, not a statistical comparison. The record does not provide event types, severity descriptions for these other events, timing, or an analysis of the difference between groups. Because the trial used a crossover schedule, the group labels describe treatment exposures, and the figures should not be treated automatically as counts from separate sets of participants.
Deaths are recorded as null for both groups, so death counts are not reported in the registry record. The adverse-event information should be read alongside the missing outcome analyses, not as evidence about the primary distress endpoint. The record does not report a formal safety comparison or an interpretation of the observed counts.
12. What the Result Does, and Does Not, Mean
The registry record establishes that a randomized, double-blind crossover study of magnesium and placebo for tinnitus was conducted, with 38 participants enrolled. It describes two treatment sequences, each including magnesium, placebo, and a 2-week washout. It also specifies a patient-reported distress rating as the primary outcome and lists Tinnitus Handicap Inventory comparisons as secondary outcomes.
What the record does not establish is the numerical result for the primary question. It contains no reported mean distress values, treatment contrast, confidence interval, p-value, or analysis result. There is therefore no basis in the registry record to say whether distress ratings were higher or lower during one treatment period, how large any difference was, or how precisely it was estimated. The same limitation applies to the listed secondary outcomes.
The design and endpoint descriptions are not outcome findings. A trial's Phase III label, randomized allocation, masking, and completion status do not substitute for observed results. Likewise, the fact that a distress rating was measured does not show what participants reported. The recorded adverse-event counts address a different question and do not resolve the missing efficacy analysis.
General statistical principles can explain why a crossover analysis should account for repeated observations and why incomplete ratings can affect interpretation. They cannot determine which analysis was actually conducted or recover an effect estimate absent from the record. Missing-data methods, handling of treatment order and period, and any multiplicity strategy are not reported in the registry record.
The appropriate reading is therefore limited: the registry describes the question and design, but does not provide numerical evidence with which to quantify the primary outcome comparison. Any conclusion beyond that would require analysis results not reported in the registry record.
13. Why This Trial Matters Statistically
This trial is statistically informative as an example of how a study's design can be clear while its outcome evidence remains unavailable in the registry record. The randomized, double-blind crossover structure indicates that the comparison was intended to use two treatment periods and two treatment sequences. The primary endpoint is also described in specific terms: a single-item patient-reported rating of tinnitus distress on a 0-10 scale, summarized as a mean with standard deviation.
Those design details matter because the analysis should reflect how observations were collected. In a crossover study, the same participant can contribute ratings under both treatments, creating paired data. Treatment sequence, time period, possible carryover, and incomplete follow-up can all affect how a comparison should be estimated. The registry describes the sequence and washout but does not report how these elements were handled analytically. This makes the record useful for understanding the intended structure, while limiting evaluation of the results.
The endpoint also illustrates why measurement and reporting are separate steps. Naming a patient-reported measure and its scale helps define what investigators intended to assess. It does not supply the observed distribution, treatment contrast, or uncertainty. The note that not all subjects completed the distress scale makes reporting of analysis counts and missing-data handling especially relevant; those details are not reported in the registry record.
Finally, a completed study with 0 registered analyses should not be confused with a finding of no effect. It means the record does not contain numerical results for the registered outcomes. The distinction is important for evidence synthesis: without estimates and their precision, the study cannot contribute a quantitative primary-outcome comparison based on this registry record alone.
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 trial-specific details needed to interpret the design and outcomes are not reported in the registry record. Eligibility criteria and participant characteristics are not described in the summary, so the enrolled population cannot be characterized beyond the condition of tinnitus and the enrollment count of 38. The record does not report how participants were recruited, the randomization method, or who was masked.
The treatment schedules are described, including magnesium at 532 mg daily, 25-day treatment periods, and a 2-week washout. However, the registry does not explain why these durations were chosen or report adherence, discontinuations, or whether participants completed both periods. It also does not describe how the crossover analysis handled treatment order, period effects, or possible carryover.
The primary endpoint description notes that not all subjects completed the distress scale, but does not report how many observations were available or how missing ratings were handled. The assessment timing is described as pre-treatment and post-treatment, up to four weeks, without numerical results tied to those measurements. The record does not identify an analysis population or provide an outcome estimate and precision measure.
Although secondary Tinnitus Handicap Inventory outcomes are listed across all subjects and by sex, no numerical results are reported. The record does not provide a statistical analysis plan, multiplicity approach, interim-analysis information, or the trial's own sample-size justification. Serious adverse-event counts are recorded, but deaths are not reported and the registry does not detail the other adverse-event types. These limitations restrict both outcome interpretation and assessment of how completely the trial is represented by its registry results.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: A Trial of Magnesium Dependent Tinnitus — NCT01273883.
- Registry record last updated 2015-04-30; status last verified 2015-04.
- Results first posted 2015-01-14.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
The registry describes a completed, randomized, double-blind Phase III crossover trial sponsored by Mayo Clinic, enrolling 38 subjects with tinnitus. One sequence received magnesium at 532 mg daily for 25 days, a 2-week washout, and then placebo for 25 days; the other received placebo first and magnesium second.
The primary outcome was a single-item Tinnitus Distress Rating on a 0-10 scale, summarized as a mean and standard deviation. The record notes that not all subjects completed the scale. Secondary outcomes included average Tinnitus Handicap Inventory comparisons across all subjects, all men, and all women.
No analyses are registered, and numerical outcome results are not reported in the registry record. Serious adverse events affected 0 participants in each group; other adverse events affected 7 in the magnesium group and 3 in the placebo group. Death counts are not reported in the registry record.