HYPEROXIA Responses and ROS: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for HYPEROXIA Responses and ROS (NCT05958303), a randomized na study. The primary outcome is Cerebral Blood Flow in Normoxia, Male vs Female.

2. Clinical Question

3. Trial Design

This is a randomized, double-masked crossover study sponsored by the University of Wisconsin, Madison. The registry lists the phase as NA and the study status as completed. In a crossover design, participants receive more than one study condition, so outcomes can be measured under each condition in the same person. Here, the two conditions were antioxidant cocktail and placebo, with normoxia measurements collected during MRI over two study visits.

The treatment schedules differed in their contents, not in the stated timing: both involved an initial dose 120 minutes before MRI and a second dose 60 minutes before MRI. The antioxidant cocktail included vitamin C, vitamin E, and alpha lipoic acid; the placebo condition involved placebo doses at both times. The record does not report the order-allocation procedure, the length or presence of a washout period, or details of how masking was maintained.

The enrollment field reports 24. The brief summary says 30 participants were expected to be enrolled, described as 15 males and 15 females. For the primary outcome, the record says all 19 participants completed both conditions, while analyses were performed on 18 participants, described as 11 males and 8 females, because one participant’s brain imaging data were not accessible at the time of the report. These statements are retained as reported; the registry record does not explain the differences among the enrollment and analysis counts.

The primary outcome timeframe is up to 6 months. The brief summary says participants could expect two study visits over a 6 month period. Specific visit intervals, treatment order, and any other protocol details beyond these descriptions 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.

Before assignment: No pre-assignment details to report.

FIrst Condition

Washout Period (24 Hours)

Reasons for not completing this period:

Second Condition

Analysis population for the primary outcome, as defined in the registry: All 19 participants completed both conditions (placebo and antioxidant) under baseline conditions. Analyses were performed on 18 participants (11 males, 8 females), as one participant's brain imaging data were not accessible at the time of this report.

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.

Population: baseline data for participants used in analysis only

6. Primary Endpoint

The registry lists the primary outcome as Cerebral Blood Flow in Normoxia, Male vs Female, measured over up to 6 months.

The primary endpoint is cerebral blood flow (CBF) under normoxia, expressed in mL/100g/min. CBF is a continuous measurement: each participant has a numerical value rather than a result classified simply as present or absent. The registry specifies the mean as the summary measure and standard deviation as the measure of spread. A mean describes the group’s average level, while the standard deviation describes how much individual measurements vary around that average.

CBF is used in this study to examine regulation of blood flow in the brain under the stated study conditions. The study’s title and summary frame the research around sex, mechanism, and stress, including a question about the role of reactive oxygen species in regulating CBF. The posted primary-outcome description concerns measurements under normoxia following antioxidant or placebo conditions. It does not establish that every planned research question or condition is represented in the posted primary result.

The endpoint title specifies a male-versus-female question, but the listed comparison estimate is for male participants under antioxidant cocktail versus placebo. The registry also posts mean and standard deviation summaries for female participants under both conditions, but does not list a formal female treatment estimate or a formal sex comparison. Those summaries describe the observed measurements; they do not by themselves establish a tested contrast.

7. Results Posted in the Registry

• Male Antioxidant Cocktail: mean 34.00 versus 30.00 on control; difference 4.00 (95% CI -1.85 to 9.85), standardized effect d = 0.57; z-test p = 0.180.

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes CBF as a continuous outcome summarized with a mean and standard deviation. The mean is the arithmetic average of the recorded values in a group. The standard deviation describes dispersion around that average: a larger value indicates more variation among measurements, while a smaller value indicates measurements are more closely clustered. Neither statistic alone describes the full distribution of an outcome.

What does a mean difference describe?

A mean difference expresses the contrast between two group means in the outcome’s original units. The posted male estimate is 4.0 mL/100g/min for antioxidant cocktail versus placebo. The comparison uses the male placebo mean of 30.0 and the male antioxidant mean of 34.0. This estimate describes the direction and size of the observed contrast on the CBF scale; it does not alone show how precisely that contrast is known or whether the study analysis accounted for the crossover design.

How should the confidence interval be read?

A confidence interval gives a range of estimates compatible with the observed data under the assumptions of the method used to construct it. The male comparison’s 95% interval runs from -1.85 to 9.85 mL/100g/min. Because this interval includes zero, it includes no mean difference as one compatible possibility, as well as differences in either direction. The endpoints are not a range containing 95% of individual participants’ measurements. They quantify uncertainty about the estimated contrast, not the spread of individual CBF values.

What does the p-value contribute?

The unadjusted p-value for the listed male comparison is 0.18. A p-value measures how unusual data at least as inconsistent with a specified null model would be, if that null model and the analysis assumptions held. It is not the probability that the null hypothesis is correct, nor does it measure clinical importance. The term “unadjusted” means the posted value is not described as corrected for multiple comparisons. The record does not report a multiplicity adjustment or the complete statistical analysis plan.

For a continuous outcome, a standard error describes the estimated uncertainty of a statistic, such as a mean or contrast. The registry lists standard errors of 2.111 for each male group mean in the comparison information. A standard error is not the same as the standard deviation: the latter describes variation among measurements, while the former describes uncertainty in an estimated quantity. The record does not explain the method used to obtain these standard errors.

Why does the crossover design matter?

In a crossover study, each participant can contribute measurements under more than one condition. Those observations are usually correlated because they come from the same person. An analysis that accounts for pairing can use information about each participant’s change across conditions; an analysis that treats measurements as independent may not use that information and can represent uncertainty differently. This is a general statistical point, not a claim about the method used in this trial. The registry record does not report the model, the handling of within-participant correlation, or whether treatment order or period effects were assessed.

The arm summaries are reported separately for males and females and for each condition. They describe group averages and variation, but do not substitute for a formal contrast. The endpoint title raises a male-versus-female question, yet the listed inferential comparison is male antioxidant versus male placebo. Without a reported sex contrast and its uncertainty, the group means alone should not be interpreted as a statistical test of a sex difference.

The sample-size illustrations use the observed male mean difference as their reference effect and consider stated fractions of that effect. Those figures are planning scenarios, not results from the trial and not estimates of the original design rationale. They rely on the listed assumptions of a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The registry does not report the original sample-size justification or whether those assumptions match the trial’s planned analysis.

Finally, a statistically interpretable estimate depends on the analysis population, missing-data handling, and prespecified outcome and comparison. The record identifies one participant whose imaging data were inaccessible at report time but does not describe imputation or other missing-data procedures. It lists four outcome measures and no secondary outcomes posted, while the count of analysis entries is zero. The posted summaries and comparison are therefore available, but the registry does not supply a full account of the inferential procedures behind them.

10. Confidence Intervals and Precision

The male mean difference is 4.0 mL/100g/min, and its 95% confidence interval extends from -1.85 to 9.85 mL/100g/min. The interval is broad enough to include zero and values on both sides of zero. This means the estimate does not pin down a single direction or a narrowly defined magnitude. The posted p-value of 0.18 is consistent with the interval’s inclusion of zero, though the interval and p-value convey different aspects of the comparison.

Precision refers to how narrowly an estimate is determined by the data and analysis. A narrow interval indicates less uncertainty about the estimated contrast than a wide interval, under the method’s assumptions. It does not establish that the estimate is free of bias, that the model is appropriate, or that the result is clinically important. Here, the interval should be read alongside the limited analysis information and the crossover design. The registry record does not state whether within-participant correlation was incorporated into this comparison, so the details needed to evaluate the interval’s construction are not reported.

The mean and standard deviation summaries provide context for the group measurements, but their uncertainty is not the same as uncertainty in the contrast. The registry gives standard deviations of 7.0 for each male group, and 10.0 and 7.0 for the female antioxidant and placebo groups. No confidence intervals are listed for the group means or for a female treatment contrast. A formal sex comparison is also not reported in the registry record.

Accordingly, the male estimate is best understood as an imprecise posted contrast rather than a definitive estimate of the effect across the study population. The confidence interval describes uncertainty under the analysis method; it does not resolve missing information about the method, the unavailable imaging data, or the unreported contrasts.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm, not total events. They illustrate the participant counts associated with 80% or 90% power under specified assumptions, for planning around the observed male contrast. The assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Scenarios consider detecting 100%, 75%, or 50% of the observed effect. The original trial’s sample-size assumptions and justification are not reported in the registry record.

For each effect scenario, the 80% power column indicates the participants per arm that the planning calculation associates with an 80% chance of detecting an effect of that stated size if the assumptions hold. The 90% power column gives the corresponding planning figure for a 90% chance. These are design illustrations, not observed outcomes or guarantees that a future study will reach a particular result. They are not observed power.

The effect fraction is relative to the observed contrast: planning for a smaller fraction means aiming to detect a smaller difference. Smaller effects generally require more participants to distinguish them from random variation at the same significance and power settings. The displayed values are based on a two-arm normal-approximation calculation. The registry does not say that this calculation reflects the trial’s crossover design or the methods used for its original planning.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 4.000; pooled standard deviation σ = 7.000.
2. n = 2 × (1.96 + 0.842)² × 7.000² / 4.000² = 48.1, rounded up to 49 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 4                      # observed difference in means
sigma <- 7                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(5958303)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 49 (80% power), 65 (90% power)
 75% of observed effect: n per arm = 86 (80% power), 115 (90% power)
 50% of observed effect: n per arm = 193 (80% power), 258 (90% power)
power.t.test: 49.1 
Simulated power at n = 49 per arm: 0.798 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures, but no secondary outcomes are posted. It also lists zero analysis entries. This does not establish which outcomes or comparisons were prespecified in the original protocol, whether analyses were performed but not entered as analysis records, or whether all planned results are represented. The full statistical analysis plan and the original protocol are not reported in the registry record.

The posted male comparison has an unadjusted p-value of 0.18. The record does not report a multiplicity correction or explain how the primary contrast was selected in relation to other outcomes and comparisons. When several outcomes or contrasts are tested, the chance of at least one result appearing noteworthy can increase; adjustment procedures can address that issue, though the appropriate approach depends on the analysis plan. This is general statistical context, not a claim that a particular adjustment was required or used in this study.

The stated analysis population requires careful attention. The primary-outcome description says 19 participants completed both conditions, while analyses were performed on 18 participants, identified as 11 males and 8 females. It attributes the reduced analysis to one participant’s brain imaging data being inaccessible at the time of the report. The registry does not reconcile the stated counts, explain whether the inaccessible data were excluded from every analysis, or describe imputation or another missing-data method.

The record does not report whether participants were analyzed according to randomized treatment order, how deviations were handled, or whether the analysis accounted for period and sequence effects. It also does not report whether the primary analysis population was defined before results were examined. These omissions do not prove that the procedures were absent; they mean the procedures cannot be assessed from the registry record.

Because this is a crossover study, within-person dependence and missing observations across conditions can affect both the analysis set and uncertainty estimates. The record states that participants completed both conditions but provides limited detail about the outcome-level data used for each contrast. Without a fuller account of the analysis model, missingness, and multiplicity strategy, the posted estimates can be described, but their relationship to the original planned analysis remains uncertain.

14. 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.

Most frequent non-serious adverse event terms

The adverse-event record separates serious adverse events, other adverse events, and deaths by sex and treatment condition. No serious adverse events are reported in any listed group, and no deaths are reported. For other adverse events, the record lists one event-afflicted male participant under antioxidant cocktail and none in the other listed groups. These are the registry’s reported counts; they do not establish that no unreported events occurred.

The group records give the number at risk and the number affected. For male participants, 11 were at risk under placebo and 11 under antioxidant cocktail; for female participants, 8 were at risk under each condition. The event counts are presented separately for each condition. Because the study uses a crossover design, the same participant may appear in more than one condition’s group records. The figures should not be added to create a count of unique participants.

Adverse-event counts are descriptive and do not by themselves establish whether an event was caused by a study condition. The registry does not provide event descriptions for the one other adverse event, details about severity or timing, or an assessment of relatedness. Zero recorded serious events is not proof that a treatment is risk-free, particularly in a study of this size and duration.

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

The posted results describe CBF measurements under normoxia for antioxidant cocktail and placebo conditions, separated by sex. The listed male contrast is a mean difference of 4.0 mL/100g/min, with a 95% confidence interval from -1.85 to 9.85 and an unadjusted p-value of 0.18. This estimate is uncertain: its interval includes no difference and also allows contrasts in either direction.

The record does not provide a formal female treatment contrast or a formal male-versus-female estimate, despite the wording of the endpoint title. The reported group means can be read as descriptive summaries, but they cannot replace a specified comparison with an estimate of uncertainty. Nor do these results by themselves establish that reactive oxygen species caused any observed pattern; the registry describes the study’s purpose but does not report a mechanistic analysis in the posted results.

The study population described in the brief summary is healthy adults aged ≥18 to ≤40 years. The registry also lists cerebrovascular disorders as a condition, but the summary does not describe the participants as having a cerebrovascular disorder. The results therefore should not be generalized beyond the studied population on the basis of this record alone.

The outcome is a physiological measure, not a direct measure of how participants feel, function, or experience a clinical event. The record does not establish a clinically important threshold for CBF, and it does not provide evidence about longer-term outcomes. The observed means and contrast are not, by themselves, evidence of medical benefit or harm.

In short, the posted information gives a limited descriptive and inferential account of normoxia CBF. Its interpretation is constrained by the confidence interval, the unreported analysis details, the unavailable imaging data for one participant, and the absence of reported estimates for some comparisons suggested by the endpoint title. The result should be understood as an estimate from this registry record, not a definitive conclusion about treatment effects or clinical outcomes.

16. Why This Trial Matters Statistically

This trial raises statistical issues that are especially relevant to small crossover studies. Because participants are measured under more than one condition, within-person comparisons may be informative, but they require methods that account for the dependence between measurements. The registry identifies the crossover design yet does not report how that dependence was handled in the listed comparison. That gap limits assessment of the precision estimate and the analysis assumptions.

The record also illustrates why the research question, outcome title, and posted contrast need to be read separately. The endpoint title emphasizes male versus female CBF, while the listed estimate compares antioxidant cocktail with placebo among males. Female summaries are present, but a formal female contrast and a formal sex comparison are not. Clear alignment between a question and its reported estimate is essential for interpreting what an analysis actually addresses.

Precision is another central issue. The male contrast’s confidence interval includes zero and spans values on both sides of it. A point estimate alone would conceal that uncertainty. The interval and the unadjusted p-value should be considered together, while recognizing that neither resolves questions about model specification or clinical importance.

Finally, the registry records differing enrollment and analysis statements, and one participant’s imaging data were inaccessible at report time. The record does not explain the count differences or describe missing-data handling. These details matter because the analysis population and the treatment of incomplete outcomes influence what the estimate represents. The study is a useful example of how transparent reporting of design, analysis, missingness, and contrasts supports statistical interpretation.

17. 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 registry record leaves several trial-specific limitations difficult to assess. It reports enrollment of 24, while the brief summary describes a planned enrollment of 30; the primary-outcome description says 19 completed both conditions and 18 were analyzed. It does not reconcile these figures. The analysis population is also described as 11 males and 8 females, and one participant’s imaging data were inaccessible at the time of reporting.

The record does not report the treatment sequence, washout arrangements, or whether period, order, or carryover effects were considered. These details can matter in crossover studies. It also does not describe the statistical model, the handling of within-participant correlation, the missing-data procedure, or a multiplicity plan. The original sample-size justification and planned analysis assumptions are not reported in the registry record.

The listed inferential result is limited to the male antioxidant-versus-placebo contrast. The record gives group summaries for females but no formal female contrast, and it does not list a formal male-versus-female estimate. Although four outcome measures are listed, no secondary outcomes are posted and no analysis entries are listed. The record does not make clear how the posted contrast relates to all originally planned outcomes or analyses.

The study description concerns healthy adults aged ≥18 to ≤40 years and reports CBF under normoxia. The registry does not establish how far results generalize beyond that population or measurement condition. Adverse-event details are also limited: descriptions, timing, severity, and relatedness are not reported for the one other adverse event. These limits reflect what is not documented in the registry record and should not be taken as proof that the unreported procedures or information did not exist.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: HYPEROXIA Responses and ROS — NCT05958303.
• Registry record last updated 2026-07-07; status last verified 2026-07.
• Results first posted 2026-07-07.
• 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.

21. Record Summary

NCT05958303 is a completed, randomized, double-masked crossover study sponsored by the University of Wisconsin, Madison. It examines cerebral blood flow under normoxia following antioxidant cocktail and placebo conditions. The intervention contains vitamin C, vitamin E, and alpha lipoic acid; placebo is administered on the same stated schedule before MRI. The primary outcome is a continuous measure reported as mean CBF in mL/100g/min, with standard deviations describing spread.

The posted male comparison is a mean difference of 4.0 mL/100g/min, with a 95% confidence interval from -1.85 to 9.85 and an unadjusted p-value of 0.18. Group summaries are also reported for females, but a formal female contrast and a formal sex comparison are not listed. The record reports no serious adverse events or deaths and one other adverse event in the male antioxidant group.

Important analysis details, including crossover modeling, missing-data handling, multiplicity procedures, and the original sample-size rationale, are not reported in the registry record. The record also gives differing enrollment and analysis counts without reconciling them.