Omega Tots Long Term Follow-up: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Omega Tots Long Term Follow-up (NCT05191823), a randomized na study. The primary outcome is General Cognitive Ability Score(Differential Ability Scales, Second Edition-DAS-II).

2. Clinical Question

The clinical question is about a group-level score, not whether each child experienced a particular change. The registry describes the study as a continuation of the Omega Tots trial and says its purpose is to follow participants from the original study to assess long-term effects of the toddlerhood supplement. It does not report the original study’s enrollment details or treatment adherence for this follow-up.

3. Trial Design

This is a randomized, triple-masked, parallel-group continuation study. The registry lists an enrollment of 377 and identifies children born preterm and child development as conditions of interest. The study follows participants from the original Omega Tots trial, NCT01576783, to a single visit when children are between 8.5 years and 10.5 years old. The record lists Sarah Keim as sponsor.

The two arms are DHA+AA and placebo. The arm description identifies the placebo as a corn oil supplement. The study is not described as a new toddlerhood intervention; rather, it follows participants who took part in the earlier trial. The registry does not report the original trial’s randomization procedures, the treatment duration, or the allocation ratio for this follow-up record. It also does not report whether the follow-up visit assessors were masked separately from other study personnel.

The primary outcome is a continuous score on the DAS-II. Secondary outcomes include cognitive, educational, motor, body-composition, and behavioral measures. The record lists 23 outcome measures and posts results for 20 secondary outcomes. It lists no reported analyses. The summaries include group means and standard deviations, while the mean differences and related inferential quantities described in the statistical interpretation are simple, unadjusted recalculations from those posted summaries.

The registry lists the study as active, not recruiting. Its recorded start date is 2021-12-01, and its primary completion date is 2024-06-25. The record does not report the follow-up participation rate, how children were selected for invitation, or whether the analysis included all eligible participants from the original study.

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 General Cognitive Ability Score(Differential Ability Scales, Second Edition-DAS-II), measured over A single study visit when the child is between 8.5 years to 10.5 years.

The primary endpoint is the General Conceptual Ability score from the Differential Ability Scales, Second Edition (DAS-II), assessed at a single visit when the child is between 8.5 years and 10.5 years old. It is a continuous measure intended to assess general cognitive ability and to help identify cognitive strengths and weaknesses. The registry describes the score range as 30 to 170, with a mean of 100 and a standard deviation of 15. Higher scores indicate better performance on this measure.

The study reports the mean and standard deviation in each arm. The DHA+AA group mean is 94.3, with a standard deviation of 14.8; the placebo mean is 96.9, with a standard deviation of 16.6. The comparison is expressed as the DHA+AA mean minus the placebo mean, so a negative estimate indicates a lower observed group mean in the DHA+AA arm. The posted mean difference is -2.6 points.

A group mean is useful for comparing average performance across randomized groups, but it does not describe every child’s score or the range of individual experiences. The primary endpoint is one aspect of long-term development; it does not capture all cognitive, educational, behavioral, or health outcomes. The registry does not report a threshold defining a clinically important difference on this score, so the practical meaning of a particular point difference cannot be determined from the record alone.

7. Results Posted in the Registry

• Docosahexaenoic Acid + Arachidonic Acid: mean 94.30 versus 96.90 on control; difference -2.60 (95% CI -6.12 to 0.92), standardized effect d = -0.17; z-test p = 0.148.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Grooved Pegboard Task

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Docosahexaenoic Acid + Arachidonic Acid: mean 104.80 versus 102.00 on control; difference 2.80 (95% CI -3.91 to 9.51), standardized effect d = 0.09; z-test p = 0.414.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Docosahexaenoic Acid + Arachidonic Acid and the control. The interval gives the range of effects that remain compatible with the data.

Select Subtest From the Wechsler Intelligence Scales for Children, Fifth Edition (WISC-V)

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Docosahexaenoic Acid + Arachidonic Acid: mean 94.60 versus 93.60 on control; difference 1.00 (95% CI -2.51 to 4.51), standardized effect d = 0.06; z-test p = 0.576.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Docosahexaenoic Acid + Arachidonic Acid and the control. The interval gives the range of effects that remain compatible with the data.

Select Subtests From the Kaufman Test of Educational Achievement, Third Edition (KTEA-3)

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Docosahexaenoic Acid + Arachidonic Acid: mean 91.50 versus 94.30 on control; difference -2.80 (95% CI -6.71 to 1.11), standardized effect d = -0.16; z-test p = 0.161.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Docosahexaenoic Acid + Arachidonic Acid and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes extend beyond general cognitive ability to include motor performance, selected measures of intelligence and educational achievement, body composition, executive function, and teacher-reported behavior. Together, they provide a broader set of developmental domains than the primary endpoint alone. They do not, however, replace the primary question: the primary result remains the comparison of DAS-II General Conceptual Ability scores at the follow-up visit.

The overall pattern is not a single consistent shift across every measured domain. The reported comparisons vary in direction, and the unadjusted intervals for the secondary comparisons described in the statistical results include no difference. This variability is one reason not to use a collection of isolated estimates to tell a simple story about a broad effect. Outcomes can differ in their scales, measurement properties, and relevance, so their results should not be combined informally into a single conclusion.

Many outcome measures create a multiplicity problem. Even when each comparison is considered separately, the chance of at least one apparently unusual result increases as more comparisons are explored. The registry record does not report a multiplicity adjustment, a prespecified hierarchy among secondary outcomes, or reported inferential analyses. Accordingly, unadjusted secondary findings carry less weight than a prespecified primary comparison and should be considered supportive or exploratory, not confirmatory evidence on their own.

The registry lists 23 outcome measures and posts results for 20 secondary outcomes. That distinction does not reveal why results for the remaining measures are absent, and it does not establish whether those measures were not collected, not analyzed, or simply not posted. The reason is not reported in the registry record. A complete interpretation of the secondary evidence would require clarity about outcome selection, missing measurements, analysis populations, and the planned approach to multiple comparisons.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Grooved Pegboard Task
• Select Subtest From the Wechsler Intelligence Scales for Children, Fifth Edition (WISC-V)
• Select Subtests From the Kaufman Test of Educational Achievement, Third Edition (KTEA-3)
• Anthropometrics-Body Composition (Height)
• Anthropometrics-Body Composition (Weight)
• Anthropometrics-Adiposity
• Behavior Rating Inventory of Executive Function, 2nd Edition (BRIEF-2)
• Select Subscales From the Teacher Report Form 6-18

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous, so the registry reports a mean and standard deviation for each arm. The mean describes the average score in a group; the standard deviation describes how dispersed scores are around that group average. The mean difference compares the two averages. Here, the comparison is defined as the DHA+AA mean minus the placebo mean, so negative values indicate a lower average score in the DHA+AA group and positive values indicate a higher average score in that group.

What does the confidence interval describe?

A confidence interval gives a range of estimates compatible with the observed data under the statistical method used. It communicates precision as well as direction: a narrower interval indicates greater precision than a wider interval. For the primary mean difference, the interval runs from -6.122 to a value above zero. Because it spans zero, the data are compatible with no difference as well as with differences in either direction. The interval does not identify which value is the true effect, and it does not assign a probability to any one value.

How should the p-value be read?

The reported p-value of 0.148 is an unadjusted recalculation from the posted means, standard deviations, and group sizes. It is not listed as a reported analysis in the registry record. In general, a p-value measures how unusual data at least this incompatible with a null model would be if that model and the test assumptions were correct. It is not the probability that the null model is true, and it does not measure the size or importance of an effect. An unadjusted p-value also does not account for the number of outcomes considered.

The posted group summaries permit a simple, unadjusted comparison of means. Such a comparison treats the arm-level summaries as the basis for estimating the difference and its uncertainty. It does not incorporate covariates, account for any clustering, or adjust for other comparisons. The registry record does not report whether the study’s own analysis used a different model, covariate adjustment, or other prespecified methods. No reported analyses are listed, so the recalculated quantities should not be mistaken for a sponsor-reported inferential result.

Why can variability matter?

For a continuous outcome, greater within-group spread makes it harder to estimate a group mean precisely when other factors are held constant. The standard deviations indicate the scale of variation in scores, while the standard error describes uncertainty in an estimated mean. In general, standard errors tend to decrease as the number of observations increases and tend to increase as the data become more variable. These summaries do not show the shape of each group’s score distribution or whether model assumptions were checked.

Over-dispersion is a general concern in some statistical models, especially when observed variation exceeds what a model assumes. When that occurs, standard errors and confidence intervals can be too small if the extra variation is ignored. The primary endpoint is analyzed as a continuous score, and the registry record does not report a model assessment or identify over-dispersion as a problem. It would therefore be inappropriate to claim that it did or did not affect this analysis.

What does randomization contribute?

Random assignment is intended to make treatment groups comparable on average at the start of a trial, including for factors that were not measured. It does not guarantee that every group characteristic will be balanced, particularly in a follow-up subset. The registry identifies the study as randomized, but it does not report details of the randomization sequence, allocation concealment, or the composition of the follow-up analysis population. The long-term comparison also depends on which original participants returned and had the outcome assessed; those details are not reported in the registry record.

How should the secondary comparisons be considered?

The registry lists many outcome measures, and multiple unadjusted comparisons raise a multiplicity concern. In general, examining more outcomes creates more opportunities for apparently notable findings to arise by chance, even if each individual test uses a conventional significance threshold. A multiplicity procedure can control aspects of this problem, but the registry record does not report such a procedure or a hierarchy for interpreting outcomes. The secondary estimates are therefore best treated as exploratory descriptions rather than as independent confirmatory evidence.

The calculations for planning illustrations use the observed effect as a reference and vary the fraction of that effect to be detected. The assumptions listed for those illustrations are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. General planning calculations of this kind depend on the chosen effect size and assumptions; they do not establish what the original investigators planned. The original design assumptions and sample-size justification are not reported in the registry record.

11. Confidence Intervals and Precision

The primary mean difference is -2.6 points, with a confidence interval from -6.122 to a value above zero. This interval includes zero, so the posted result does not pin down the direction of the underlying group difference. It is compatible with a lower average in the DHA+AA group, no average difference, or a higher average in that group. The interval’s span is important: the point estimate alone gives a single value, while the interval shows the uncertainty around that estimate.

Precision is also reflected in the standard errors of the group means, which are 1.185 for DHA+AA and 1.351 for placebo. The group standard deviations, 14.8 and 16.6, describe variation among individual scores and should not be confused with uncertainty in the mean. The mean difference is small relative to the observed spread of scores, but the record does not specify a clinically important threshold against which to judge its size.

The confidence interval is based on an unadjusted recalculation from the posted summaries. It does not account for possible adjustment in a study analysis that is not reported, missing outcomes, selection into follow-up, or multiplicity across outcomes. Its interpretation is therefore conditional on the calculation and the available summaries. Greater precision would mean a narrower interval, but a narrow interval alone would not determine whether a difference is meaningful; that requires a defensible clinical or developmental threshold, which is not reported in the registry record.

12. 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 participants and not total events. The event-based convention does not apply to these continuous outcomes. For each assumed effect size, the 80% power column gives the illustrated number of participants per arm for an 80% chance of detecting an effect of that size under the stated assumptions, if that effect and the assumptions were correct. The 90% power column gives the corresponding per-arm planning figure for a higher target chance of detection.

The planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is the stated fraction of the observed effect. The figures are planning illustrations computed from the observed effect, not observed power. They are not the original trial’s design targets: the original design assumptions and sample-size justification are not reported in the registry record.

Rows for 100%, 75%, and 50% of the observed effect illustrate how the target effect size changes planning needs. A smaller effect is harder to distinguish from random variation, so it requires more participants per arm for the same target power. The calculations are not guarantees that a future study will attain the stated power, because their usefulness depends on whether the assumed effect, variability, allocation, and analysis approach are reasonable. The planning curve should be read as a visual representation of this same relationship, not as an additional observed study result.

13. 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 = -2.600; pooled standard deviation σ = 15.711.
2. n = 2 × (1.96 + 0.842)² × 15.711² / -2.600² = 573.2, rounded up to 574 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 <- -2.60000000000001                      # observed difference in means
sigma <- 15.7110381996695                     # 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(5191823)
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 = 574 (80% power), 768 (90% power)
 75% of observed effect: n per arm = 1,020 (80% power), 1,365 (90% power)
 50% of observed effect: n per arm = 2,293 (80% power), 3,070 (90% power)
power.t.test: 574.2 
Simulated power at n = 574 per arm: 0.796 (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.

14. Multiplicity, Missing Data and Analysis Populations

The record lists a broad outcome set, including the primary cognitive score and secondary cognitive, educational, motor, body-composition, and behavioral measures. It reports 23 outcome measures and posts results for 20 secondary outcomes. When many outcomes are examined, unadjusted tests can produce apparently noteworthy results by chance. In general, multiplicity methods or a prespecified outcome hierarchy can help control how multiple comparisons are interpreted. The registry record does not report a multiplicity adjustment, a hierarchy for confirmatory testing, or a statistical analysis plan that explains how the outcomes were to be handled.

The registry lists no reported analyses. The inferential comparisons discussed for the posted summaries are unadjusted recalculations, rather than reported sponsor analyses. The record does not report whether the investigators used covariate adjustment, how they handled repeated or correlated outcomes, or what model was prespecified. These omissions limit the ability to determine whether the recalculated comparisons match the intended analysis.

Missing-data procedures and analysis populations are also not reported in the registry record. The record does not state how many eligible original-trial participants were invited or attended follow-up, how many had missing outcome values, how missingness was handled, or whether the analysis followed an intention-to-treat principle. It does not describe exclusions or the characteristics of participants with and without an available primary outcome. These details matter because a follow-up comparison can be influenced by who returns and whose data are analyzed.

The record posts group-specific outcome counts, but those counts can vary between outcomes. Without a reported accounting of missingness and analysis populations, the reasons for those differences cannot be established. No conclusion about bias from missing data is justified from the posted summaries alone; its presence and direction are not reported in the registry record.

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

The primary posted result is a mean DAS-II General Conceptual Ability score of 94.3 in the DHA+AA group and 96.9 in the placebo group, with an unadjusted mean difference of -2.6 points. The confidence interval includes zero, and the unadjusted p-value is 0.148. These statistics describe the observed group summaries and the uncertainty around their difference. They do not establish a clear separation between the groups, nor do they prove that the groups are identical.

The result does not show what happened to each individual child. Group averages can conceal a range of scores and experiences, and the standard deviations indicate variation within both arms. The registry provides no clinical-importance threshold for the DAS-II endpoint, so the practical significance of a difference of this size cannot be inferred from the score comparison alone. A higher score indicates better performance on the measure, but the endpoint is not a complete account of a child’s development.

This is a long-term follow-up of participants who received DHA+AA or placebo during toddlerhood in the original study. It concerns a later assessment, when the children were between 8.5 years and 10.5 years old. The results do not directly address the effects of starting supplementation at that later age, and they do not by themselves establish effects on outcomes that were not measured or posted.

The randomized design is relevant to interpreting group differences, but this follow-up record does not report enough detail about participation, missing outcomes, analysis populations, or statistical procedures to assess all sources of uncertainty. The findings should therefore be read as the available long-term group summaries, with the limitations of the posted information in mind. No medical recommendation follows from these registry results.

16. Why This Trial Matters Statistically

Long-term follow-up asks a different question from an intervention trial assessed during treatment: whether group differences are present on later measures among participants who can be assessed years afterward. This record is statistically useful because it reports a continuous cognitive endpoint with group means, standard deviations, and a comparison that can be interpreted in terms of both direction and precision. The confidence interval is essential: the point estimate alone would not show how broadly the data remain compatible with other values.

The study also illustrates why a single primary endpoint and a wider set of secondary outcomes should not be treated alike. A primary measure gives the analysis a central question, while numerous additional outcomes can help explore related domains but increase the risk of chance findings. Without a reported multiplicity strategy or analysis plan, the secondary results are better understood as a broader descriptive picture than as multiple independent confirmations.

Long-term studies also depend on follow-up participation and complete measurement. The registry record does not report the analysis population, missing-data approach, or reasons for differences in outcome counts. Those details are statistically consequential because the observed follow-up group may not represent everyone who entered the original trial. Their absence does not prove that the estimates are biased, but it limits assessment of how robustly they generalize to the original participants.

Finally, the planning illustrations show how required sample size depends on the effect a future study aims to detect. They are distinct from the actual trial design rationale, which is not reported. Keeping observed results, unadjusted recalculations, and hypothetical planning separate helps prevent descriptive follow-up findings from being mistaken for a definitive test of every possible long-term effect.

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 most important trial-specific limitation in the registry record is the lack of detail about follow-up participation. The study is described as a continuation of the original Omega Tots trial, but the record does not report how many original participants were eligible, invited, or assessed, or how follow-up participants differed from those without posted outcomes. This makes it difficult to judge whether the observed groups represent the original randomized groups at follow-up.

The record also does not report missing-data methods, analysis-population definitions, or reasons that outcome counts vary across measures. It lists 23 outcome measures and posts results for 20 secondary outcomes, but does not explain why results for the other measures are absent. The absence of that explanation prevents a complete assessment of outcome reporting and completeness.

The posted primary comparison is based on group summaries, and the record lists no reported analyses. The statistical plan, any covariate adjustment, and any multiplicity procedure are not reported in the registry record. As a result, the unadjusted recalculations cannot be confirmed as matching the investigators’ intended analysis. The record also does not report a threshold for a clinically important difference in the primary score, limiting interpretation of practical importance.

Adverse events were not assessed during this follow-up study, according to the record. That means these results do not provide a follow-up adverse-event assessment. The record does not report treatment adherence during toddlerhood or other details that would help characterize exposure. These omissions should be treated as limitations of the available registry information, not as evidence that an unreported procedure or outcome occurred.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Omega Tots Long Term Follow-up — NCT05191823.
• Registry record last updated 2026-08-11; status last verified 2026-07.
• Results first posted 2026-08-11.
• 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

This randomized, triple-masked, parallel-group continuation study follows participants from the original Omega Tots trial. The registry lists an enrollment of 377 and describes a single assessment visit when children are between 8.5 years and 10.5 years old. The primary outcome is DAS-II General Conceptual Ability score.

The posted primary mean is 94.3 for DHA+AA and 96.9 for placebo. The unadjusted mean difference is -2.6 points, with a confidence interval that includes zero. The registry lists no reported analyses; inferential comparisons described from the posted summaries are unadjusted recalculations. The record does not report the analysis plan, missing-data methods, or multiplicity procedures. Adverse events were not assessed during this follow-up study.