Impact of Vitamin D Supplementation on Lactation Associated Bone Loss: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Impact of Vitamin D Supplementation on Lactation Associated Bone Loss (NCT00903344), a randomized na study. The primary outcome is Change in Bone Mineral Density (BMD) in HIP at 6 Months.

2. Clinical Question

As a general statistical framing, the clinical question is comparative: whether the mean change in a measured bone-density outcome differs between randomized groups. Answering that question requires a between-group estimate and information about its precision, not merely separate summaries for each group. Those comparative results are not reported as an estimable analysis in the registry record.

3. Trial Design

The record identifies a randomized, parallel-group trial with no masking. Its status is completed. The recorded enrollment is 22. The phase is listed as not applicable. The study start is recorded as 2009-12, and primary completion as 2012-06. The named sponsor is Leigh Eck, MD. These registry entries describe the design and administrative record; they do not establish how many participants contributed to each outcome or how the randomization sequence was generated.

The two arms are titled Vitamin D - Experimental and Multivitamin - Active Comparator. The experimental regimen is 4000IU vitamin D3 in a tablet taken daily with a multivitamin. The active-comparator regimen is a multivitamin with a 400IU vitamin D tablet. The record describes the study model as parallel, meaning the arms are separate groups rather than successive treatment periods within the same participants. Since masking is listed as none, the registry describes the trial as unmasked; it does not specify which people involved in conduct or assessment knew treatment assignment.

The primary outcome is change in hip bone mineral density from baseline to six months, expressed in grams/cm^2. The arm-level outcome summaries list 9 participants for the vitamin D arm and 10 for the multivitamin arm. These are the counts attached to the posted primary outcome summaries; they should not be substituted for the overall enrollment entry or interpreted as a full account of participant flow. Reasons for the difference between the outcome counts and enrollment, as well as allocation procedures and analysis-population definitions, are not reported in the registry record.

The registry also names secondary outcomes concerning 25-hydroxyvitamin D levels and bone mineral density at the hip and spine at follow-up. It reports no analysis as estimable for the continuous two-arm comparison described in the skip note. Thus, the design fields identify the intended randomized comparison, while the posted primary summaries alone do not provide a formal comparative result.

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:

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 Bone Mineral Density (BMD) in HIP at 6 Months, measured over Change from Baseline to 6 months.

The primary endpoint is change in bone mineral density at the hip from baseline to six months. The measure is reported in grams/cm^2, and the endpoint parameter is the mean. In practical terms, each arm’s posted value summarizes the average change in measured hip bone density over the stated follow-up interval among the participants included in that arm’s summary.

As a general explanation, bone mineral density is a quantitative measure of mineral content in bone over a specified area. It can be used as a research outcome when a study is concerned with changes in bone mass, because it gives a numerical measure that can be compared over time or between groups. A change-from-baseline endpoint focuses on movement during the observation period rather than only the final measurement. The hip is one of the anatomical sites named for assessment in this record; the record also lists spine outcomes among its secondary outcomes.

The endpoint should be read as a measured surrogate outcome within this study, not as a direct count of fractures or a measure of long-term fracture risk. The registry’s stated primary outcome is a six-month change in hip bone mineral density; it does not report a fracture endpoint as the primary outcome. Interpretation of a mean change also depends on the group summaries and the precision of a comparison. Although standard deviations are posted for each arm, a two-arm estimate and confidence interval are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a mean change represent?

For a continuous endpoint, a mean is the arithmetic average of the measured values in a group. Here, the endpoint is change from baseline to six months in hip bone mineral density, and the unit is grams/cm^2. A negative group mean indicates that the average recorded change was below baseline; a positive group mean indicates that the average was above baseline. This is a general interpretation of signed change scores, not a claim about the cause of the changes. The record reports means for both arms but does not report an estimable two-arm analysis.

A within-group mean and a between-group contrast answer different questions. The mean describes the average change in one arm. The contrast asks how the average change differs between arms. In a randomized trial, the contrast is the main statistical quantity for assessing the comparative outcome, because changes may occur in both groups over time for reasons beyond the assigned regimen. Reporting the two arm means is informative descriptively, but it does not on its own supply a contrast, its uncertainty, or a test of the comparison.

How should the standard deviation be read?

The standard deviation is a measure of how spread out individual observations are around a group mean. A larger standard deviation means the observations are more dispersed around that mean; it is not the size of the mean’s uncertainty and it is not a range containing every participant. In general, uncertainty about a mean depends on both the variability of observations and the amount of information available. A confidence interval for a mean or a between-arm contrast would express that uncertainty in a way the standard deviation alone does not.

The posted standard deviations are 0.014 in the vitamin D arm and 0.122 in the multivitamin arm. They describe the arm-level variation associated with the posted outcome summaries. Without participant-level information and a reported comparative analysis, they do not explain the source of that variation, establish why the groups differ in spread, or provide a confidence interval for the treatment contrast. They should not be interpreted as evidence of a treatment effect by themselves.

Why does the missing comparative estimate matter?

A confidence interval gives a range of values compatible with the data under the assumptions of the analysis. Its width conveys precision: a wide interval indicates less precision than a narrow interval. A p-value, when reported, addresses a statistical test under a specified null hypothesis and analysis plan; it is not a measure of effect size or clinical importance. Neither a confidence interval nor a p-value for the primary two-arm comparison is reported in the registry record. The registry’s note says values are missing or not estimable for that comparison, so the arm summaries should not be treated as a substitute for those missing inferential results.

Random allocation is a design feature intended, in general, to make treatment groups comparable on average at the start of a trial. It does not guarantee that all observed characteristics will be identical, especially in a study with limited enrollment. It also does not make missing outcome data disappear or ensure that a particular statistical method was used. The record identifies randomized allocation but does not report the sequence-generation method, concealment procedures, or a detailed analysis plan. Since masking is listed as none, expectations or knowledge of assignment could be relevant in some trial processes; how that issue was handled is not reported.

What do the planning assumptions mean?

The record describes a sample-size planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. Such a calculation is a planning exercise: it asks how many participants per arm might be required under specified assumptions to detect a target effect with a chosen power. It does not report the trial’s original design justification, and the registry record does not report the trial’s own sample-size rationale.

A planning illustration is not observed power. Observed power is not a substitute for interpreting the estimated effect and its confidence interval, and a sample-size calculation based on an observed effect can be especially dependent on the effect estimate used. The assumptions describe the calculation, not a verified feature of the trial. Equal allocation in the illustration should not be read as proof that the actual outcome counts were equal. The registry does not report numeric planning results in the record, so no required sample size should be inferred from these assumptions.

As a general matter, normal-approximation calculations rely on assumptions about the sampling distribution of an estimate. The appropriateness of an approximation depends on the design, outcome distribution, and analysis. The registry does not report diagnostic checks or the statistical procedure behind an estimable primary comparison. Because that comparison is marked not estimable, the planning assumptions cannot supply the missing treatment-effect estimate or its precision.

What does a parallel randomized design imply?

In a parallel design, participants are assigned to one of the arms and the groups are followed over the study period. This differs from a crossover arrangement in which the same participant receives multiple regimens in different periods. The registry identifies a parallel randomized model and a six-month primary timeframe. Further details such as visit schedules, handling of measurements outside the target time, and whether baseline values were used in an adjusted model are not reported in the registry record.

For a continuous endpoint, analysts may use different methods to compare arms, including a comparison of change scores or a model adjusting for baseline outcome values. These methods can answer related but not identical statistical questions and may use information differently. This is general background; the record does not identify which approach was planned or used, and it reports no estimable two-arm primary analysis. No specific method should therefore be attributed to this trial beyond what the registry states.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Vitamin D - Experimental", "Multivitamin - Active Comparator")
n   <- c(9, 10)
m   <- c(-0.041, 0.011)
sp  <- c(0.014, 0.122)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Vitamin D - Experimental  9  -0.041  0.014  -0.052  -0.030
CARM  Multivitamin - Active Comparator  10  0.011  0.122  -0.076  0.098

11. Multiplicity, Missing Data and Analysis Populations

The registry lists five secondary outcomes in addition to the primary outcome, and reports six outcome measures in total. The named secondary outcomes concern 25-hydroxyvitamin D levels at follow-up and bone mineral density at the hip or spine at follow-up. Multiple outcomes create a general statistical issue: when many hypotheses are tested, the chance of at least one apparently notable result can rise if no adjustment or prespecified interpretation strategy is used. Adjustment methods and outcome hierarchies can address that issue in different ways, but the registry record does not report a multiplicity plan or an adjustment for multiple testing. It is therefore not possible to determine from this record how secondary findings were intended to be interpreted collectively.

The registry lists zero analyses and notes that values are missing or not estimable for a two-arm comparison of the continuous endpoint. It does post arm-level means and standard deviations for the primary outcome. This combination means that descriptive summaries are available, but the record does not provide an inferential analysis to assess the primary between-arm contrast. Details such as model specification, treatment of baseline values, confidence-interval construction, and statistical software are not reported in the registry record.

The primary-outcome summaries list counts of 9 in the vitamin D arm and 10 in the multivitamin arm, while enrollment is recorded as 22. The record does not provide a participant flow account that reconciles these entries. It does not report how missing measurements were handled, whether participants were excluded from an analysis, or whether an intention-to-treat, per-protocol, or other analysis population was used. These omissions prevent a full assessment of whether missingness could affect the posted arm summaries or a comparative estimate.

As a general principle, missing-data methods depend on why data are absent and on assumptions about their relationship to observed outcomes. Complete-case summaries and model-based approaches can rely on different assumptions. Without information about missingness and the analysis population, neither a particular explanation for the outcome counts nor a particular missing-data mechanism can be assigned to this trial.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

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 serious adverse event entries list 12 participants at risk and 0 affected in the Vitamin D - Experimental group. The Multivitamin - Active Comparator group lists 10 participants at risk and 0 affected. The record lists no top serious-event terms. These figures describe the registry’s serious adverse event fields; they do not establish that no events could have occurred outside the reporting scope or period captured by the record.

For other adverse events, the experimental group lists 12 at risk and 1 affected, while the active-comparator group lists 10 at risk and 0 affected. These are counts as entered in the registry, not a comparative safety analysis. No rate, risk difference, or statistical uncertainty is reported, and one should not infer a comparative safety effect from the counts alone. The record does not provide event descriptions for the non-serious event in the experimental group.

Death entries are null for both arms. A null entry is not the same as a reported count of zero; the death figures are not reported in the registry record. More generally, adverse-event fields depend on the event definitions, observation period, and completeness of reporting. Those details are not available, so the posted counts should be read narrowly as registry entries rather than as a comprehensive evaluation of safety.

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

The posted primary outcome summaries describe average change in hip bone mineral density from baseline to six months in the two arms. The vitamin D arm has a mean change of -0.041 grams/cm^2, and the multivitamin arm has a mean change of 0.011 grams/cm^2. The standard deviations are 0.014 and 0.122, respectively. The registry record marks the two-arm comparison as missing or not estimable, so it does not report a formal estimate of the between-arm difference or its precision.

That distinction limits what the result means. The values allow a reader to describe the direction of each arm’s posted mean change. They do not establish that the regimens caused those changes, and they do not show how precisely the average comparative effect is known. Without a comparative estimate and confidence interval, it is not possible to assess from the registry result whether the data are compatible with a range of potentially meaningful differences or with little difference. A missing or non-estimable comparison is not evidence that the regimens are equivalent, nor is it evidence that one is superior.

The enrollment entry is 22, while the primary summaries carry arm-level outcome counts of 9 and 10. The record does not explain the relationship between those figures. The reason for the discrepancy is not reported in the registry record, and the available information does not justify attributing it to missingness, withdrawal, or any other specific cause. That uncertainty about the analysis population further narrows interpretation.

The primary endpoint is a measure of bone mineral density, not fractures or long-term health outcomes. The record describes a six-month change at the hip and lists other bone-density and vitamin D outcomes as secondary measures. No conclusion about later outcomes should be drawn from the posted primary summaries. In short, the record supplies descriptive results for the primary measure but does not provide an estimable comparative result or enough methodological detail to determine the precision and robustness of a treatment-effect estimate.

14. Why This Trial Matters Statistically

This trial is statistically informative as an example of the difference between a randomized design and a reported comparative result. Randomization identifies the intended contrast between regimens, but readers still need an analyzed between-arm estimate to assess the outcome comparatively. Here, the registry records the randomized parallel design and posts arm-level means, yet it marks the continuous two-arm comparison as missing or not estimable. The design description and the available inferential evidence are therefore not the same thing.

The primary endpoint is continuous, and the registry gives both means and standard deviations. Those summaries provide useful descriptive information, but they cannot replace a treatment-effect estimate with uncertainty. The arm-level counts also differ from the overall enrollment entry, and the registry does not explain the analysis population or participant flow. These features illustrate why statistical interpretation depends not only on outcome values but also on clear reporting of who was analyzed and how the comparison was conducted.

The record also names several secondary outcomes. When multiple outcomes are evaluated, readers need to know whether they were prespecified, how findings were prioritized, and whether multiplicity was considered. The registry does not report those details. Their absence does not determine what analyses were performed, but it limits the conclusions that can be drawn from any set of outcome summaries.

Finally, the sample-size planning assumptions are distinct from observed trial evidence. A planning illustration using an observed effect and stated assumptions is not a report of observed power and does not explain the original design rationale. Clear separation of planning, descriptive estimates, and inferential comparisons helps prevent readers from treating calculations or separate arm summaries as stronger evidence than they are. This record makes those distinctions especially relevant because its primary comparative analysis is not estimable.

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 limitations specific to this record constrain interpretation. First, the registry does not report an estimable two-arm analysis for the primary continuous outcome. The posted arm-level means and standard deviations are not accompanied by a between-arm estimate, confidence interval, or p-value. As a result, the magnitude and precision of the comparative effect cannot be assessed using the registry record.

Second, the outcome counts attached to the primary summaries are 9 in the vitamin D arm and 10 in the multivitamin arm, whereas the enrollment entry is 22. The registry does not explain how these figures relate or provide participant flow information. It also does not report missing-data handling, reasons for absent outcome measurements, or a defined analysis population. No cause for the difference can be inferred from the record.

Third, the trial is listed as unmasked, but the registry does not specify which individuals were aware of assignment or how measurement and other trial procedures were conducted. Randomization is recorded, but the sequence-generation and allocation-concealment methods are not reported. The statistical analysis plan, baseline adjustment, and details of the primary analysis are also not reported.

Finally, the registry names secondary outcomes but does not report how multiple outcomes were handled statistically. The primary outcome is a six-month bone-density change, so the record does not directly answer questions about fractures or longer-term outcomes. Adverse-event entries are limited, and death fields are not reported. Together, these reporting gaps mean that the record is best read as a source of design details and descriptive summaries rather than a complete account of the trial’s comparative statistical findings.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Impact of Vitamin D Supplementation on Lactation Associated Bone Loss — NCT00903344.
• Registry record last updated 2014-08-18; status last verified 2014-08.
• Results first posted 2014-08-18.
• 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

NCT00903344 is a completed randomized, unmasked, parallel-group trial titled Impact of Vitamin D Supplementation on Lactation Associated Bone Loss. The registry records enrollment of 22 and a primary endpoint of change in hip bone mineral density from baseline to six months, measured in grams/cm^2. The experimental regimen is 4000IU vitamin D3 daily with a multivitamin; the active comparator is a multivitamin with a 400IU vitamin D tablet.

The posted primary summaries give mean changes of -0.041 in the vitamin D arm and 0.011 in the multivitamin arm. The registry marks the two-arm continuous comparison as missing or not estimable. It does not report a comparative estimate, confidence interval, or p-value, or explain the primary outcome counts of 9 and 10 relative to enrollment. Secondary outcomes are listed, but multiplicity and missing-data methods are not reported in the registry record.