Triglyceride Effects on Blood Flow in the Human Brain: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Triglyceride Effects on Blood Flow in the Human Brain (NCT05218018), a na na study. The primary outcome is Cerebral Blood Flow Global.

2. Clinical Question

3. Trial Design

This was a completed, single-group study sponsored by the University of Washington. The registry record lists the study phase as NA, allocation as NA, and masking as none. The intervention was a lipid drink, and the arm description says there was only one arm. Accordingly, the study does not provide a randomized treatment-versus-control contrast. The baseline measure serves as the reference for the primary change endpoint; it is not a concurrent control group.

The registry lists enrollment as 30. The study summary describes the objective as characterizing cerebral blood flow changes after a high-fat drink in older adults, with a time-course assessment and analyses of global and regional change. The stated primary endpoint is global cerebral blood flow at 2 hours minus baseline. The registry record does not give details of the time points beyond this primary endpoint, the imaging protocol, participant eligibility criteria, or how the secondary outcome was defined.

The listed start date is 2020-03-01, the primary completion date is 2022-01-13, and the status is completed. The study summary describes the work as feasibility pilot data intended to inform a future R01 application. That stated purpose is useful context: the record presents the study as an investigation of acute physiological response, not as a controlled test of clinical benefit. The record does not report a sample-size justification or a detailed protocol for the future application.

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

Analysis population for the primary outcome, as defined in the registry: One participant's MRI data had to be excluded as the baseline data did not pass quality control metrics

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 Cerebral Blood Flow Global, measured over Value at 2 hours minus value at baseline.

The primary endpoint is change from baseline in global cerebral blood flow at 2 hours, expressed in ml/100g/min. Cerebral blood flow is the amount of blood moving through brain tissue, and the study summary explains that it is assessed using functional MRI. It describes blood flow as closely coupled to brain metabolism, which is the rationale for using this measure to investigate an acute response to a lipid drink.

The endpoint is a change score: the value at 2 hours is compared with the baseline value for the same participant. A change score can describe whether the measurement moved upward or downward over that interval, while a group mean summarizes the average change across the analyzed observations. The standard deviation describes how much individual change values vary around that mean. These are general interpretations of the stated mean and standard deviation; the registry record does not give their numerical values for this outcome.

The record notes that one participant’s MRI data had to be excluded because the baseline data did not pass quality-control metrics. It does not state the final number included in the primary analysis. The numerical mean change and its standard deviation are not reported in the registry record, so the magnitude and variability of the endpoint cannot be described from the available results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes the primary outcome as a continuous measure summarized by a mean and standard deviation. The endpoint is the change in global cerebral blood flow from baseline to 2 hours. The following explanations are general statistical context, not a claim that the registry used methods that it does not describe.

What does a mean change represent?

For each participant with usable measurements, a change score compares the later measurement with that participant’s baseline measurement. The group mean of these changes describes the average direction and magnitude of change among the observations included in the analysis. Positive and negative values would have different interpretations according to the subtraction order specified in the endpoint: the record defines the timeframe as value at 2 hours minus value at baseline. However, no observed mean is reported in the registry record, so no direction or magnitude can be assigned.

A mean can be informative while still concealing variation among individuals. Participants may have similar changes or widely different ones, and the mean alone does not reveal that pattern. The standard deviation is a descriptive measure of spread around the mean. It is not the same as a confidence interval: a standard deviation describes variation among observed values, whereas a confidence interval expresses uncertainty about an estimated quantity under a statistical model. The registry record identifies standard deviation as the dispersion measure but does not report its value or a confidence interval for the primary endpoint.

Why is the comparison within one group limited?

A baseline-to-follow-up comparison uses each participant as their own reference. This can be useful for describing an acute response, but it does not supply the counterfactual information that a concurrent control group would provide. In general, the counterfactual is the outcome that would have occurred over the same interval without the intervention. Because the registry describes only one arm and no randomized comparison, an observed change cannot by itself separate the intervention from other time-related influences. This is a design limitation, not a statement about whether a change occurred.

For a continuous change score, a statistical analysis might estimate the group mean change and its uncertainty, or assess whether the data are compatible with a specified null value. Those are general possibilities, not methods established by this record. The registry record does not report a test statistic, a p-value, a confidence interval, covariate adjustment, or the specific inferential procedure used for the primary endpoint. Without such details and the outcome estimate, statistical significance and precision cannot be evaluated.

What does the planning illustration describe?

The record describes sample-size assumptions for a planning illustration based on the observed effect, not the trial’s own design. The assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. This is a planning exercise and should not be mistaken for a description of the single-group study’s enrollment design. It also is not observed power. A planning estimate can illustrate how a proposed future study might be sized under selected assumptions, but it does not show the probability that the completed study detected an effect.

The record does not report the numerical sample-size outputs or the observed effect used in the illustration in the information available for this explanation. It is therefore not possible to discuss those planning estimates or verify their inputs. More generally, such estimates depend on the assumed effect, variability, significance level, allocation, and analysis model. If an assumed effect is uncertain, the resulting sample-size illustration is uncertain as well.

Why can variability affect planning?

In general, greater variability makes a given mean difference harder to distinguish from random variation, while lower variability can make it easier to estimate a mean precisely. For repeated measurements, the variability of change also depends on the relationship between baseline and follow-up measurements. The registry record does not report the relevant numerical variability or correlation, so these considerations cannot be quantified for this study.

The sample-size assumptions describe equal allocation between two arms, whereas the completed study is listed as single-group. That difference reinforces the need to treat the illustration as prospective planning context rather than as a reconstruction of the completed study’s analysis. The registry record does not state that this illustration was the trial’s original design rationale, nor does it report a sample-size justification for the completed study.

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("Intervention")
n   <- c(29)
m   <- c(-2.2)
sp  <- c(3.5)
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  Intervention  29  -2.200  3.500  -3.531  -0.869

11. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures and one analysis, but the information available does not describe the full analysis plan, identify all outcomes as primary or secondary, or state whether any multiplicity adjustment was applied. When multiple outcomes or comparisons are examined, the chance of obtaining an apparently unusual result by chance can increase. General approaches to addressing this issue include prespecifying a primary outcome, adjusting inference, or treating secondary findings as exploratory. The record does not establish which approach was used, so no adjustment should be assumed.

The primary endpoint is identified as change in global cerebral blood flow at 2 hours. The study summary also describes time-course and regional analyses, but the record does not provide their results or enough detail to determine how they relate to the two listed outcome measures. The number of listed analyses alone does not show how many statistical tests were performed. A detailed multiplicity strategy is not reported in the registry record.

For missing data and analysis populations, the record states that one participant’s MRI data had to be excluded because baseline data did not pass quality-control metrics. It does not report the final number included in the primary analysis, how missing or unusable follow-up measurements were handled, or whether any imputation was performed. It also does not define an intention-to-treat, per-protocol, or other analysis population. Enrollment is reported as 30, but that entry should not be substituted for the number analyzed. The available information does not permit assessment of whether the exclusion or any other missing data could have affected the result.

12. Safety Results

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

Deaths

Other (non-serious) adverse events

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

The registry reports serious adverse events for the intervention group: 30 participants were listed as at risk, and 0 as affected. Deaths were reported as 0. The record lists no top serious-event terms. These figures describe what was entered in the registry for the listed group; they do not establish that every possible adverse event was actively assessed or that no non-serious events occurred.

The at-risk count is a safety reporting denominator, not a statement about the number included in the primary cerebral blood-flow analysis. The record separately notes that one participant’s baseline MRI data failed quality-control metrics, but it does not explain whether that exclusion affected the safety reporting population. Nor does the record provide detail about the duration or completeness of adverse-event surveillance. A zero in the serious-event count means that no serious events are recorded in this entry; it should not be interpreted as proof of no risk or as a comparative safety estimate.

Because this is a single-group record without a control arm, the serious-event figures do not support a comparison of safety between treatments. The available counts should be read as registry-reported observations for the intervention group, not as evidence of a causal safety effect.

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

The study addresses a focused physiological question: whether global cerebral blood flow changes from baseline to 2 hours after a lipid drink in older adults. The endpoint and its measurement interval are clearly identified in the registry. The study summary also places this question within an interest in acute brain metabolic response and describes the work as feasibility pilot data for a future application.

What the result means cannot be determined from the information reported for the endpoint. The registry record does not report the numerical mean change or its standard deviation, and it gives no confidence interval or inferential result. Consequently, it is not possible to describe the observed direction, magnitude, variability, or precision of the primary outcome. Neither a positive nor a negative finding should be inferred from the endpoint definition or from the study’s stated rationale.

Even if a before-and-after change were available, the single-group design would support a descriptive conclusion about measurements over time in this group, not a controlled estimate of the drink’s effect. Without a concurrent control group, changes associated with the intervention cannot be separated from other explanations for change. The record also does not report the detailed analysis plan or the results for the described regional and time-course assessments.

The study does not establish a cognitive effect, a lasting change, or an effect on Alzheimer disease. The summary discusses background hypotheses about diet, metabolism, and Alzheimer disease, but those statements are rationale rather than findings from the primary endpoint. The listed outcome is a cerebral blood-flow measure, not a clinical outcome. The meaning should therefore be confined to the acute measurement question, and even that question cannot be answered quantitatively from the endpoint data reported in the registry record.

14. Why This Trial Matters Statistically

This study is statistically notable for the distinction between a within-group change and a controlled treatment comparison. A baseline measure can provide a useful reference for describing subsequent measurements, especially when the scientific aim is to characterize an acute physiological response. But the absence of a separate control group means that such a change does not isolate the intervention from other influences that may operate over time. Recognizing that distinction prevents descriptive results from being overstated as causal evidence.

The registry also illustrates why a clearly named endpoint is not enough for statistical interpretation. The measure, units, and assessment interval are specified, and the outcome is defined as a continuous mean. Yet the numerical estimate and its variability are not reported in the information. Without those values, readers cannot judge the direction, size, or precision of the observed response. Endpoint definition and outcome reporting are both needed to evaluate a result.

The baseline MRI quality-control exclusion also highlights the importance of reporting analysis populations and missing-data handling. Enrollment does not automatically indicate how many observations contributed to an endpoint, and a stated exclusion does not reveal the final analysis denominator. Transparent reporting of these details helps readers understand the basis of an estimate and assess its limitations.

Finally, the planning illustration is conceptually different from the completed study’s design. It uses assumptions for a proposed two-arm study, while this registry describes a single group. Treating a planning exercise as planning—not as observed power or as the original trial design—keeps the interpretation aligned with the actual record. These distinctions matter when pilot work is used to inform future research.

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.

The primary limitation is that the numerical primary outcome is not reported in the registry information available for interpretation. Without the mean change, standard deviation, or an uncertainty interval, the observed response and its precision cannot be assessed. The record identifies a baseline MRI quality-control exclusion but does not state the final analysis population, so the endpoint denominator is also unclear.

The single-group design has no separate control arm. A within-group change can describe measurements across the study interval but cannot, on its own, distinguish an intervention-associated change from other time-related influences. The registry lists no masking, and it does not provide further details about the imaging protocol, measurement reliability, timing beyond the primary endpoint, or handling of repeated measures.

The study summary refers to global and regional analyses and a time-course assessment, while the registry lists two outcome measures and one analysis. The available record does not give sufficient detail to determine the full set of analyses, the status of each outcome, or how multiplicity was considered. It also does not report a detailed statistical analysis plan, a sample-size justification, or how missing data beyond the stated quality-control exclusion were managed.

Finally, the registry’s condition listing and study rationale should not be mistaken for evidence of a clinical effect on Alzheimer disease. The primary endpoint is a cerebral blood-flow measure at 2 hours, and the record does not report cognitive outcomes or a controlled comparison. The listed safety counts likewise do not provide a comparative safety assessment.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Triglyceride Effects on Blood Flow in the Human Brain — NCT05218018.
• Registry record last updated 2023-02-08; status last verified 2023-01.
• Results first posted 2023-02-08.
• 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

NCT05218018, titled “Triglyceride Effects on Blood Flow in the Human Brain,” is a completed, single-group study sponsored by the University of Washington. It lists enrollment as 30 and describes a lipid drink intervention in older adults. The primary endpoint is change from baseline in global cerebral blood flow at 2 hours, measured in ml/100g/min and summarized as a mean with standard deviation.

The record notes that one participant’s baseline MRI data failed quality-control metrics. It reports 0 serious adverse events among 30 listed as at risk, and deaths as 0. The numerical primary outcome, its variability, the final analysis population, and detailed methods for missing data and multiplicity are not reported in the registry record. The study summary describes the work as feasibility pilot data for future research.