Effect of Dietary Supplemental Fish Oil in Alleviating Health Hazards Associated With Air Pollution: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effect of Dietary Supplemental Fish Oil in Alleviating Health Hazards Associated With Air Pollution (NCT03255187), a randomized na study. The primary outcome is Biomarkers of Antioxidant Activity-Total Antioxidant Capacity (TAC) and Superoxide Dismutase (SOD).

2. Clinical Question

The trial’s stated aim was to evaluate whether dietary fish oil supplementation could protect against cardiopulmonary alterations linked to air pollution. That aim is broader than the primary endpoint alone: the registry also lists outcomes concerning blood pressure, insulin resistance, skin biomarkers, and lung function. These outcomes represent several aspects of the trial’s stated health-hazard focus, but their presence in the registry does not itself show that any changed between groups. The key statistical question would be whether measurements differed between the randomized groups over the specified follow-up, with uncertainty quantified for the comparison. The registry record does not report the result needed to answer that question for TAC or SOD.

3. Trial Design

The registry describes a randomized, quadruple-masked, parallel-group trial sponsored by Fudan University. It is marked completed and lists enrollment of 70. The recorded start date is 2017-09-09 and the primary completion date is 2018-01-13. The study is listed as phase NA. The registry record does not report further details about the randomization procedure, allocation concealment, or the roles covered by quadruple masking.

One group received fish oil supplementation and the other received sunflower seed oil supplementation, described as placebo. Both regimens were 2.5 g/day, taken as two 1.25-g capsules daily for 4 consecutive months. The parallel design means the two assigned groups were followed as distinct groups rather than each participant serving in turn as their own treatment comparison. Random assignment is intended, in general, to make treatment groups comparable on average, while masking is intended to limit the influence of treatment knowledge on care, measurement, or assessment. The registry does not specify how these procedures were implemented.

For the primary outcome, blood samples were taken at the end of each round of 4 follow-ups, with an interval of 2 weeks, during the last 2 months of intervention. The endpoint description says the reported outcome values refer to means of measurements at 4 follow-ups. Samples were separated into serum and stored at -80 ℃ within 30 minutes. TAC and SOD are the two named biomarkers, measured in U/ml.

The registry also lists secondary outcomes covering blood pressure, insulin resistance, skin inflammation and oxidative stress biomarkers, lung function, and skin antioxidant biomarkers. It identifies 19 outcome measures overall. The registry record does not report the target number of participants for each group, a sample-size justification, detailed analysis populations, or the statistical procedures used to compare groups.

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.

Periodfrom Enrollment to First Follow-up

Reasons for not completing this period:

Period From First to Second Follow-up

Reasons for not completing this period:

Period From Second to Third Follow-up

Period From Third to Fourth Follow-up

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 Biomarkers of Antioxidant Activity-Total Antioxidant Capacity (TAC) and Superoxide Dismutase (SOD), measured over Blood samples are obtained at the end of each round of 4 follow-ups with an interval of 2 weeks in the last 2 months of intervention..

The primary endpoint concerns two biomarkers of antioxidant activity: total antioxidant capacity (TAC) and superoxide dismutase (SOD). Both are reported in U/ml. The registry describes blood collection and processing, and states that outcome values refer to the means of measurements at 4 follow-ups. Those repeated measurements are intended to characterize biomarker levels during the intervention’s later period rather than a single isolated measurement.

As a general statistical concept, a biomarker endpoint is a measured biological quantity used to assess a process of interest. TAC and SOD are identified in this record as antioxidant activity biomarkers; the registry does not provide a more detailed rationale for selecting them or define a threshold for interpreting their values. A mean can summarize the central level across repeated observations, while the standard deviation describes the spread of individual measurements around that mean. Neither summary alone establishes whether the randomized groups differ.

To interpret a treatment comparison, readers would need the group-specific results and a between-group estimate with an indication of its uncertainty. Those results are not reported in a single reduced primary comparison in the registry record. The endpoint description names both TAC and SOD, and the registry indicates multiple categories or time points that were not reduced to one comparison. Therefore, the endpoint definition is available, but a concise estimate of the primary contrast is not.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The trial is recorded as randomized, quadruple-masked, and parallel. In general, randomization assigns participants to treatment groups by chance, which can reduce systematic differences between groups at baseline. Masking can reduce the influence of knowing the assigned treatment on behavior, measurement, or assessment. The registry record does not report the particular randomization method or explain who was masked, so those implementation details cannot be evaluated.

What does the primary measure summarize?

The primary outcome names TAC and SOD, two antioxidant activity biomarkers, in U/ml. The registry describes blood samples collected at the end of each round of 4 follow-ups, spaced at intervals of 2 weeks during the last 2 months of intervention. It says the values refer to means of measurements at 4 follow-ups. In general, a mean summarizes the central value of observations. The accompanying standard deviation describes how dispersed observations are around that mean. A standard deviation is not a measure of uncertainty in the estimated group comparison; that requires an inferential quantity such as a standard error or confidence interval.

The record identifies the outcome parameter as a mean and the dispersion as standard deviation. It does not report the group-specific means and standard deviations in a single primary comparison, nor does it report a comparative estimate and confidence interval. Without those results, readers cannot assess the size, direction, or precision of a difference between randomized groups. The endpoint description is not itself evidence that the intervention changed either biomarker.

Why does the repeated-measure schedule matter?

Repeated measurements can describe how a biomarker behaves across follow-up, but statistical methods need to account appropriately for observations taken from the same participant. In general, repeated values from one person are related and should not automatically be treated as independent observations. An analysis might summarize repeated values or model their pattern, but the registry record does not say which approach was used. It also does not clarify whether the stated mean was calculated at the participant level before group summaries or by another procedure.

The registry notes that the outcome values refer to measurements at 4 follow-ups, but it does not report whether each participant contributed all scheduled measurements. It does not describe missing-data methods, rules for excluding observations, or how incomplete follow-up was handled. These omissions limit assessment of how representative the reported endpoint would be if results were available.

How should dispersion and uncertainty be distinguished?

As a general concept, standard deviation describes variability among observations, whereas a confidence interval describes uncertainty about an estimated quantity, such as a group contrast. A narrow interval generally indicates greater precision than a wide one, but its interpretation depends on the statistical model and assumptions. The registry record reports that the outcome dispersion is standard deviation; it does not supply a confidence interval for the primary contrast. No precision claim about the treatment comparison can therefore be made from the endpoint description.

What can a planning illustration say?

General sample-size calculations depend on assumptions about the effect to detect, variability, significance level, allocation, and analysis method. The planning assumptions associated with this record specify a two-sided significance level of 0.05, equal allocation, and a normal approximation, with illustrations based on fractions of the observed effect. Such illustrations are hypothetical planning scenarios, not observed power and not evidence that the original trial was designed with those assumptions. The registry record does not report the trial’s own sample-size justification. The primary outcome also was not reduced to a single comparison, so no one primary effect estimate can be used to explain the intended comparison.

What remains unavailable?

The registry record lists 19 outcome measures and zero analyses, but does not report the statistical analysis plan, model specification, covariate adjustment, treatment of repeated measures, or multiplicity procedure. It does not identify analysis populations, such as whether all randomized participants were included in the primary analysis. These are not minor reporting details: they determine how estimates are formed and what population they represent. General statistical principles can explain why these choices matter, but cannot establish which choices were made in this trial. The registry record therefore permits a description of the planned measurement and broad design, while leaving the inferential methods and primary comparative results unreported.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 19 outcome measures, with the primary outcome naming both TAC and SOD and describing measurements across 4 follow-ups. Multiple outcomes, biomarkers, or time points can create a multiplicity issue: in general, the more statistical comparisons considered, the greater the opportunity for chance findings to appear noteworthy. Statistical plans may address this by identifying a primary comparison in advance, setting an outcome hierarchy, or adjusting inference across comparisons. The registry record does not report whether any such approach was planned or used.

The record does not reduce the primary endpoint to a single comparison, and it lists zero analyses. It does not provide a statistical analysis plan, a prespecified hierarchy among the outcomes, or details of any adjustment for multiple testing. The registry record therefore does not establish how multiplicity was handled. This absence also means that no claim about the statistical significance of any outcome can be assessed from the primary results information recorded.

Missing-data handling and analysis populations are also not reported in the registry record. It is not stated whether the primary analysis included all randomized participants, only participants with measurements, or another defined group. Nor are the amount, timing, or reasons for missing measurements described. In general, missingness can affect both the precision and interpretation of estimates, and the impact depends on why observations are missing and on the analysis approach. No such approach should be inferred for this trial.

The repeated-measure schedule makes these omissions particularly relevant: the endpoint description refers to means from 4 follow-ups, but does not explain how incomplete sets of repeated measurements were treated. Without an analysis population, missing-data method, and multiplicity strategy, the record does not support a full appraisal of inferential robustness.

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 registry records two groups for adverse events. In the fish oil group, 34 participants are listed as at risk for serious adverse events and 34 for other adverse events; the corresponding affected counts are 0 and 0. In the sunflower seed oil group, 31 participants are listed as at risk for each category, with 0 serious and 0 other adverse events recorded. The death count is 0 in both groups.

These figures are counts as entered in the registry record. They indicate that no events are recorded in these categories for the listed at-risk groups. They do not, by themselves, describe how adverse events were defined, how actively they were monitored, the duration of safety follow-up, or whether event collection was complete. Those details are not reported in the registry record.

In general, an observed count of zero is not proof that the underlying risk is zero. Interpretation depends on the size of the group, follow-up, and completeness of reporting. The serious-event figures should therefore be read as registry-recorded counts, not as a guarantee that no events occurred or as a comparison establishing equivalent safety between groups.

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

The registry record documents a randomized comparison of fish oil supplementation with sunflower seed oil supplementation, a four-month regimen in each group, and a primary outcome focused on TAC and SOD. It also documents the schedule for blood sampling and lists a range of secondary outcomes. These details clarify what was studied and how the primary measurements were defined.

The record does not report a single reduced primary comparison across the biomarkers or follow-up time points. It therefore does not provide an estimate of the difference between groups, its direction, or its precision. No conclusion about whether either biomarker changed in relation to the assigned supplement follows from the endpoint description alone. The completed trial status does not fill this reporting gap.

In general, a treatment comparison is most informative when it includes an estimate of the contrast and a measure of its uncertainty, interpreted in light of the design and analysis plan. Here, the registry record does not provide a primary comparative estimate or a statistical analysis plan. The study’s multiple listed outcomes also make the unreported multiplicity strategy relevant to interpretation. These limits mean that the record can describe the trial but cannot support a statistical conclusion about the primary outcome.

The safety record lists zero serious and zero other adverse events in both groups, with zero deaths recorded. These are descriptive registry counts, not proof of absence of risk or evidence that the groups have the same safety profile. The record does not specify further monitoring or reporting details.

Accordingly, the defensible reading is narrow: the trial was designed to compare two dietary supplements in relation to health hazards associated with air pollution, and the registry defines antioxidant biomarkers as its primary outcome. The registry record does not report the comparative results needed to judge the primary outcome, nor does it report enough analysis detail to assess how estimates were produced. Its design and measurement information should not be mistaken for evidence of an outcome effect.

13. Why This Trial Matters Statistically

This trial is statistically notable for the gap between a clearly described measurement schedule and the lack of a single reported primary comparison. The registry identifies TAC and SOD, specifies the unit U/ml, and describes means over 4 follow-ups. Those details help define the endpoint, but statistical interpretation ultimately depends on the between-group estimate and its uncertainty. Without them, readers cannot evaluate the magnitude or precision of a treatment contrast.

The study also lists 19 outcome measures spanning biomarkers, blood pressure, insulin resistance, and lung function. In general, a broad outcome set calls for transparent prioritization: a prespecified primary contrast helps readers distinguish the main inferential question from exploratory comparisons. The registry record does not report a statistical analysis plan or a multiplicity approach, so that prioritization cannot be assessed from the record.

Repeated follow-up measurements add another methodological consideration. Measurements within a participant are generally related, so a method that accounts for their structure is important when estimating group differences. The registry describes the collection schedule but not the analysis method or handling of incomplete measurements. These details affect how a result should be understood, not merely how it is presented.

Finally, the recorded enrollment of 70 and the completed status do not reveal whether the trial had adequate precision for its intended question. The record does not report the original sample-size justification. Any planning illustration based on an observed effect is hypothetical and should not be read as observed power or as the trial’s original design rationale. The case illustrates why clear outcome definitions, analysis plans, missing-data reporting, and comparative estimates are all needed for a complete statistical reading.

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.

Several trial-specific details needed to evaluate the primary result are not reported in the registry record. Although the study is described as randomized and quadruple-masked, the record does not explain the randomization procedure, allocation concealment, or who was masked. It also does not describe participant characteristics or eligibility, limiting assessment of the population to which findings might apply.

The primary outcome includes TAC and SOD and measurements at 4 follow-ups, but the registry does not report a single reduced comparison. Group-level outcome estimates, a between-group effect estimate, and its uncertainty are not available in that primary-outcome presentation. The record lists 19 outcome measures and zero analyses, but does not identify a statistical analysis plan, a hierarchy of outcomes, or any adjustment for multiplicity.

For the repeated measurements, the analysis approach is not reported. It is also not stated whether every participant contributed measurements at each follow-up or how any missing observations were handled. Analysis populations, exclusions, and the extent of follow-up are not described. The sample-size justification is not reported in the registry record, so enrollment alone cannot establish the intended precision or adequacy of the comparison.

The intervention and comparator regimens are described, but adherence and other implementation details are not reported in the registry record. Safety counts are listed, but the event definitions, monitoring procedures, and completeness of event reporting are not described. These limitations are specific gaps in the record; they do not establish that the corresponding procedures were absent from the trial, only that they are not reported in the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Effect of Dietary Supplemental Fish Oil in Alleviating Health Hazards Associated With Air Pollution — NCT03255187.
• Registry record last updated 2024-04-23; status last verified 2024-04.
• Results first posted 2020-01-21.
• 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

NCT03255187 is a completed, randomized, quadruple-masked, parallel trial sponsored by Fudan University. It records enrollment of 70 and compares fish oil supplementation with sunflower seed oil supplementation, each taken at 2.5 g/day for 4 consecutive months. The primary outcome concerns TAC and SOD in U/ml, based on means of measurements at 4 follow-ups during the last 2 months of intervention.

The registry lists 19 outcome measures, but does not report a reduced primary comparison or a statistical analysis plan. It records zero serious adverse events, zero other adverse events, and zero deaths in both groups. The primary comparative results, analysis populations, missing-data methods, and multiplicity handling are not reported in the registry record.