Blueberry Consumption and Type 2 Diabetes: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Blueberry Consumption and Type 2 Diabetes (NCT02972996), a randomized na study. The primary outcome is Blood Pressure.

2. Clinical Question

The study was framed as a test of a dietary intervention against a placebo, rather than a comparison with no intervention. Its focus was on cardiometabolic measures in a defined population. The registry also lists Hemoglobin A1C as a secondary outcome. It does not report whether that secondary measure differed between groups or give the numerical findings needed to interpret any observed change.

3. Trial Design

The study is listed as randomized, triple masked, and parallel. Randomization means that assignment to the intervention groups was intended to use a chance-based process; the registry record does not describe how the sequence was generated or how assignments were concealed. A parallel design means participants were assigned to a group and the groups were compared, rather than participants crossing from one intervention to another.

The two named groups were Blueberry and Placebo. The Blueberry group received 22 g freeze-dried blueberries, and the Placebo group received 22 g placebo. The registry calls the masking triple but does not identify which groups of people were masked. It also does not report the matching details of the placebo or whether masking was assessed during the trial.

Total enrollment was 55. The record reports a start date of 2017-01-19, a primary completion date of 2018-06-21, and a status of COMPLETED. These dates describe the study record and do not supply the duration of each participant’s follow-up. The stated primary outcome timeframe was 8 weeks.

The trial’s official title specifies men with type 2 diabetes. The registry summary describes the objective as determining whether freeze-dried blueberries, compared with a blueberry placebo, would improve cardiometabolic parameters in that population. Phase is listed as NA. Further details about eligibility, recruitment, intervention adherence, allocation concealment, and the planned statistical analysis 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.

Overall Study

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 Blood Pressure, measured over 8 weeks.

The primary outcome is blood pressure, specified as systolic blood pressure and diastolic blood pressure, measured over 8 weeks. Blood pressure describes pressure in the arteries during the heart’s pumping and resting phases. Systolic and diastolic readings represent distinct components of that measurement, so they should not be treated as interchangeable or combined without a stated analysis plan.

Blood pressure is used as a cardiometabolic measure because it quantifies a physiological characteristic relevant to cardiovascular health. In a trial, comparing its values between randomized groups can help describe whether the groups’ measurements differ over the specified observation period. That general role does not establish the size, direction, precision, or clinical importance of a difference in this particular study.

The registry identifies the outcome parameter as a least-squares mean and the dispersion as a standard error. A least-squares mean is an adjusted mean from a statistical model; the registry record does not specify the model or variables used for adjustment. A standard error describes the statistical precision of an estimated mean, rather than the spread of individual participants’ measurements. The numerical blood-pressure estimates and their standard errors are not reported in the registry record, so the endpoint’s observed result cannot be interpreted quantitatively.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does randomization contribute?

In general, randomization assigns participants to study groups through a chance-based process. Its purpose is to reduce systematic differences between groups at assignment, including differences that investigators may not have measured. It does not guarantee that groups will be identical, particularly in a study with limited enrollment, and it does not resolve problems caused by missing measurements or departures from the planned analysis. This record states that allocation was randomized, but the sequence-generation and concealment procedures are not reported in the registry record.

The parallel model means the intervention groups are followed as separate groups. The study compared 22 g freeze-dried blueberries with 22 g placebo. The registry does not describe treatment adherence, participant crossover, or whether participants remained in their assigned groups for the analysis. These details matter when interpreting the contrast between assigned treatment groups and actual exposure.

What does triple masking tell the reader?

Masking is intended to limit the influence of knowledge about group assignment on study conduct, outcome assessment, or participants’ reports. The registry lists the masking as triple, but does not identify which people were masked or how masking was maintained. It also does not report whether the placebo matched the intervention in taste, appearance, or other characteristics. The label alone cannot establish the success of masking.

How should least-squares means and standard errors be read?

A mean is a measure of the average value in a group. A least-squares mean is a model-based mean, often adjusted for variables included in the model. Which variables were used, how the model was specified, and whether it accounted for baseline measurements are not reported in the registry record. A standard error expresses the precision of an estimated mean. It is not the same as the standard deviation, which describes variation among individual observations. Since the numerical means and standard errors are not reported for blood pressure, the amount of between-participant variation and the precision of the estimates cannot be assessed from the posted results.

For a comparison between groups, readers generally need the estimated difference and its uncertainty, not only separate group summaries. A confidence interval is a general way to communicate uncertainty around an estimate: narrower intervals indicate greater precision, while wider intervals indicate less precision. A p-value is another statistical summary, but it does not show the size or importance of an effect. Neither confidence intervals nor p-values for the primary outcome are reported in the registry record.

Why does the endpoint have multiple components?

The primary outcome description includes systolic and diastolic blood pressure. These are distinct measures, and a study can analyze them separately or use a prespecified approach to address multiple outcomes. The registry does not report a single reduced comparison for the primary outcome, nor does it describe how the two components were handled statistically. The actual outcome estimates are not reported in the registry record.

In general, testing several outcomes or comparisons can increase the chance of finding at least one apparently notable result by chance. A multiplicity approach may define a primary comparison, adjust inference, or otherwise explain how multiple tests are interpreted. The statistical plan and any multiplicity adjustment are not reported in the registry record. The number of listed outcome measures and analyses does not reveal whether an adjustment was used.

What is the role of the planning illustration?

The record’s planning assumptions describe an illustration based on an observed effect, using a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is described as a stated fraction of the observed effect. Such calculations are planning illustrations, not observed power: they do not show the probability that this completed trial detected an effect, and they do not replace the trial’s actual outcome estimates. The registry record does not report the trial’s own sample-size justification, the assumptions used in its original design, or a protocol-based power calculation. No numerical planning results are reported in the registry record.

More generally, a planning calculation depends on assumptions about the effect size, variability, allocation, and statistical method. If those assumptions differ from what occurs in a trial, the calculation may not describe the study’s achieved precision. No extra conclusion about sample size or power should be drawn from the enrollment figure alone.

10. Multiplicity, Missing Data and Analysis Populations

The registry identifies blood pressure as the primary outcome and describes both systolic and diastolic blood pressure. It also lists Hemoglobin A1C as a secondary outcome. The record indicates 2 outcome measures and 2 analyses, but does not state how many statistical comparisons were conducted for each outcome, which comparison was considered primary in the analysis, or whether any multiplicity adjustment was used. The statistical analysis plan is not reported in the registry record. Without that information, it is not possible to determine how the trial addressed the interpretive challenge of assessing multiple measures.

In general, multiplicity matters because each additional statistical test creates another opportunity for a result to appear notable by chance. A prespecified hierarchy, adjustment procedure, or clearly defined primary comparison can help readers understand how evidence across outcomes is evaluated. The registry information does not establish whether any such approach was planned or applied. The number of outcomes alone does not reveal the analysis strategy.

The number of participants included in each outcome analysis, the missing-data rate, and the method for handling missing observations are not reported in the registry record. It also does not report whether all randomized participants were analyzed according to their assigned group or whether another analysis population was used. These details affect how outcome estimates should be interpreted: an analysis restricted to participants with observed measurements can differ from an analysis that accounts for all randomized participants, especially if missingness is related to outcomes or group assignment. No conclusion about these possibilities can be drawn from the posted information.

The record lists total enrollment as 55 and reports 26 participants at risk in each group for the adverse-event summary. Those figures do not identify the analysis population for blood pressure or Hemoglobin A1C. Without participant flow and outcome-specific analysis counts, the relationship between enrollment and the reported safety denominators cannot be assessed.

11. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The safety record lists 26 participants at risk in the Blueberry group and 26 in the Placebo group. It reports 0 participants affected by serious adverse events and 0 affected by other adverse events in each group, with 0 deaths in each group. No serious adverse event terms are listed.

These figures describe the safety information recorded for the groups and denominators shown. A zero count means that no affected participants were recorded in that category in this registry summary; it does not prove that no adverse experience occurred, that every participant was observed for the same length of time, or that an intervention has no safety concerns. The record does not describe how adverse events were defined, how actively they were monitored, or the safety follow-up period. Those details are not reported in the registry record.

The safety denominators should not be assumed to represent the number analyzed for the blood-pressure outcome. The primary outcome analysis population and missing safety data are not reported in the registry record. The reported counts are therefore best read as the registry’s adverse-event summary, not as a complete account of every possible safety outcome.

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

The record establishes that a completed randomized, triple-masked, parallel study compared 22 g freeze-dried blueberries with 22 g placebo in men with type 2 diabetes. It names blood pressure, measured as systolic and diastolic blood pressure over 8 weeks, as the primary outcome, and lists Hemoglobin A1C as a secondary outcome. It also records the trial’s enrollment and summarizes adverse events.

Those design details do not establish what happened to blood pressure or Hemoglobin A1C. The numerical outcome estimates are not reported in the registry record. Without the group results and an estimate of the between-group contrast, the direction and magnitude of an effect cannot be described. Without uncertainty measures, the precision of any estimate cannot be judged. The registry record also does not report the analysis plan needed to understand how multiple outcomes, missing data, and participant inclusion were handled.

In general, statistical evidence and clinical importance are related but distinct questions. An estimate can be precise yet small, or uncertain even when its point estimate appears notable. Interpreting either issue requires outcome values and a clearly described comparison. Since those results are not reported in the registry record, no conclusion about the size, certainty, or clinical relevance of a blood-pressure difference is warranted from the posted information.

The adverse-event summary reports zero affected participants in the listed serious and other event categories for both groups, and zero deaths. This is a description of the record’s reported counts, not proof that there were no adverse experiences or that risks were absent. Monitoring and follow-up details are not reported in the registry record.

The study’s rationale and design identify a focused question about a dietary intervention and cardiometabolic measures. The record supports describing that question and how the comparison was organized; it does not support a claim that the intervention did or did not improve the outcomes.

13. Why This Trial Matters Statistically

This trial is statistically relevant because its primary outcome description includes separate systolic and diastolic blood-pressure measures. When an endpoint has multiple components, readers need to know whether each was analyzed separately, whether one was designated as the principal comparison, and how any multiplicity was addressed. The registry record does not report those analysis details or the numerical outcome values, making clear reporting especially important for interpretation.

The trial is also an example of the distinction between a registered study design and a complete statistical account of results. Randomization, masking, a parallel model, an enrollment figure, and a defined timeframe help describe how the comparison was organized. They do not, by themselves, tell readers the size or precision of an outcome difference. Estimates, uncertainty measures, analysis populations, and missing-data methods are also needed to evaluate the evidence.

The registry’s planning assumptions illustrate another important distinction. A sample-size calculation based on an observed effect and specified assumptions is a planning illustration, not observed power and not a replacement for the actual estimate and its uncertainty. The registry does not report the trial’s own sample-size justification. That absence limits assessment of how the original enrollment target was chosen, but it does not establish that the trial was adequately or inadequately sized.

Finally, the safety counts show why denominators and monitoring descriptions matter. Counts of zero affected participants are meaningful only in the context of the participants at risk and the event definitions and observation period. Those details are not fully reported in the registry record. The example therefore emphasizes careful separation of what is recorded from what cannot be concluded.

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 principal limitation for interpreting the trial is that numerical results for the primary outcome are not reported in the registry record. Although blood pressure is identified as the primary outcome and systolic and diastolic measures are specified, there are no posted outcome estimates, standard errors, confidence intervals, or p-values. The direction, magnitude, and precision of a between-group difference therefore cannot be evaluated from this record.

Several details needed to assess the analysis are also absent. The registry does not report the statistical model underlying the least-squares means, the covariates included, the analysis population, or the approach to missing measurements. It does not explain how the two blood-pressure components and the secondary Hemoglobin A1C outcome were handled in relation to multiple testing. These omissions prevent assessment of whether the analysis followed a prespecified plan and how robust its interpretation might be.

Enrollment is reported as 55, while the safety summary lists 26 participants at risk in each group. Outcome-specific participant counts and a flow of participants through the study are not reported in the registry record. The relationship between enrollment, the safety denominators, and the analyzed population is consequently unclear. The registry also does not describe eligibility criteria in detail, participant characteristics, adherence, or intervention discontinuation.

The record labels the study triple masked but does not identify who was masked or describe how the placebo matched the intervention. Random-sequence generation and allocation concealment are not reported. These are limits on judging implementation, not evidence that the procedures were inadequate. The single trial record also does not provide information about how its findings might apply beyond the specified population of men with type 2 diabetes.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Blueberry Consumption and Type 2 Diabetes — NCT02972996.
• Registry record last updated 2022-04-19; status last verified 2022-02.
• Results first posted 2022-04-19.
• 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 identifies NCT02972996, titled “Blueberry Consumption and Type 2 Diabetes,” as a completed randomized, triple-masked, parallel study sponsored by Albany Research Institute, Inc. Its official title specifies effects of blueberry consumption on cardiometabolic parameters in men with type 2 diabetes. Enrollment was 55; the start date was 2017-01-19, and primary completion was 2018-06-21.

The intervention was 22 g freeze-dried blueberries, compared with 22 g placebo. Blood pressure, defined as systolic and diastolic blood pressure over 8 weeks, was the primary outcome. Hemoglobin A1C was listed as a secondary outcome. The primary outcome estimates and numerical results for the secondary outcome are not reported in the registry record. The safety summary reports 0 serious adverse events, 0 other adverse events, and 0 deaths in each group, with 26 participants at risk in each group. Details of the analysis plan, missing data, and participant populations are not reported in the registry record.