Transcranial Near-Infrared Light in Healthy Subjects: a Cerebral Blood Flow Study With Diffuse Correlation Spectroscopy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Transcranial Near-Infrared Light in Healthy Subjects: a Cerebral Blood Flow Study With Diffuse Correlation Spectroscopy (NCT03740152), a na na study. The primary outcome is Change in Cerebral Blood Flow (Baseline to Week 5).

2. Clinical Question

The registry describes an investigation of whether transcranial continuous and pulsed near-infrared light are associated with a change in cerebral blood flow in healthy subjects. It also describes aims to relate that change to cognitive performance and skin pigmentation, and to assess safety and tolerability. The formal primary endpoint is the change in cerebral blood flow from baseline to Week 5. The record names change in N-Back Task accuracy and the number of participants with treatment-emergent adverse events as secondary outcomes.

This is a measurement and early evaluation question, not a randomized treatment-versus-control question. Although sham TLT is included in the scheduled treatment periods, the record describes one group receiving all three periods rather than separate arms. Whether measurements were compared within each subject, how the periods were ordered, and how any comparisons were analyzed are not reported in the registry record. The primary outcome result is also not reported in the registry record, so the stated question cannot be answered from the registered results alone.

3. Trial Design

This completed study is registered as NCT03740152, with the title “Transcranial Near-Infrared Light in Healthy Subjects: a Cerebral Blood Flow Study With Diffuse Correlation Spectroscopy.” Massachusetts General Hospital is listed as the sponsor. The registry lists the phase as NA, allocation as NA, masking as none, and model as single group. Enrollment is 10. The study start date is 2017-08-22, the primary completion date is 2019-05-16, and the status is completed.

The intervention is a device called Transcranial Light Therapy. The arm description states that all subjects will be administered 1 week of continuous TLT, 1 week of pulsed TLT, and 1 week of sham TLT. The registry record does not describe a separate control arm or randomized assignment. It also does not report the order of treatment periods, whether periods were separated by a washout, or how observations from the different periods were to be compared. Those details should not be inferred from the treatment schedule alone.

The primary outcome is change in cerebral blood flow from baseline to Week 5, measured using a Diffuse Correlation Spectroscopy signal. The registry specifies a mean as the outcome parameter and standard deviation as the dispersion measure. The secondary outcomes are change in accuracy on the N-Back Task from baseline to Week 5 and the number of participants with treatment-emergent adverse events. The summary also describes intended correlations with cognitive performance and skin pigmentation, as well as safety and tolerability aims. The analysis methods for these aims are not reported in the registry record.

A single-group design can describe measurements in the enrolled participants, but it does not create a randomized, like-for-like contrast between separately assigned groups. The record's inclusion of sham treatment does not by itself establish the method used to compare the treatment periods. Conclusions about causal effects or comparisons among periods would require details of the design and analysis that are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Change in Cerebral Blood Flow (Baseline to Week 5), measured over 5 weeks.

The primary endpoint is change in cerebral blood flow from baseline to Week 5. The registry specifies that cerebral blood flow is measured using the Diffuse Correlation Spectroscopy signal and gives the unit as mm2/s. The outcome is described as a mean, with standard deviation as the dispersion measure. These details identify the measurement and the way its distribution was intended to be summarized; they do not give the observed change.

In general, an endpoint is a defined measurement used to address a study question. A baseline-to-follow-up change is intended to describe how a measure differs over the stated observation period. For a continuous measure such as the one described, a mean can summarize the group’s average value or change, while a standard deviation describes variability among observations. The standard deviation is not the same as the precision of the mean; precision is commonly conveyed with an uncertainty interval, but such an interval is not reported in the registry record.

The registry gives the timeframe as 5 weeks and names the baseline-to-Week-5 change as the primary endpoint. The record does not report the baseline value, Week 5 value, mean change, standard deviation of change, or an inferential analysis for this endpoint. Therefore, the definition clarifies what was intended to be measured, but does not establish the size, direction, or precision of an observed change. DCS is the specified measurement method; its use alone does not indicate that a change occurred.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The methods information in the registry record is enough to identify the study’s general structure and primary measurement, but not enough to reconstruct an analysis. Statistical interpretation depends on both the definition of an outcome and the method used to summarize and compare observations. In this study, the endpoint is defined as change in cerebral blood flow from baseline to Week 5, using a Diffuse Correlation Spectroscopy signal. The record does not report the result or a statistical analysis of that endpoint.

What does a mean describe?

The registry identifies the primary measure as a mean and names standard deviation as its dispersion summary. In general, a mean is a measure of the center of observed values. A standard deviation describes how spread out those values are around their mean. These summaries answer different questions: the mean describes the average, while the standard deviation describes variability among measurements. Neither supplies an uncertainty interval for the estimated mean by itself. The registry record does not report the numerical mean, standard deviation, or an interval for the primary endpoint.

For a change endpoint, the analysis must also define what observations are paired or otherwise used to form the change. The registry names baseline and Week 5, but does not describe the detailed calculation, handling of repeated readings, or analysis population. The stated unit is mm2/s. No additional scale transformation, adjustment, or model is reported. It is therefore not possible to determine from the record whether the reported outcome, if any, would represent a raw change, an adjusted estimate, or another summary.

How should a confidence interval be understood?

In general, a confidence interval expresses uncertainty around an estimated quantity under the assumptions of the analysis. A narrower interval indicates greater precision than a wider interval, but precision is not the same as the size or clinical importance of an estimate. An interval’s interpretation also depends on the statistical model and study design. No confidence interval for the primary endpoint is reported in the registry record, so its precision cannot be assessed from the posted results.

What does the single-group structure allow?

The study is listed as single group, with allocation recorded as NA and masking recorded as none. All subjects were to receive the continuous, pulsed, and sham TLT periods. In a general within-subject design, measurements from the same participant may be related, so an analysis can need to account for that dependence rather than treating observations as independent. If treatment periods are compared, period order and possible carryover can also matter. These are general design considerations, not claims about methods used in this study. The registry record does not state the order, washout procedures, or model for repeated measurements, so it does not support a specific account of how those issues were handled.

A separate randomized control group would support a different kind of contrast from a single-group design. Here, the registry does not list a separate randomized comparison arm. The presence of a sham period in the schedule does not on its own tell the reader whether the analysis compared periods within participants, whether period assignment was randomized, or how such a comparison was performed. Those details are not reported in the registry record.

What do the planning assumptions mean?

The registry’s planning assumptions describe an illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The illustration describes detection of stated shares of the observed effect. It is a planning exercise, not the actual single-group design described in the record. Such planning figures are not observed power, and they do not show the probability that the study’s hypothesis was true or that a treatment worked. The record does not report the trial’s own sample-size justification. The numerical effect and planning outputs are not reported in the registry record.

More generally, power calculations depend on assumptions about the effect to be detected, variability, significance level, allocation, and analysis method. When those assumptions do not match the actual design or outcome analysis, planning results may not describe the study’s ability to estimate its observed outcome. Since this study is registered as single group while the planning illustration assumes equal allocation between two arms, that illustration should not be read as a description of the trial’s design.

What can be inferred from the outcome listings?

The registry lists one primary outcome and two secondary outcomes. The primary outcome is cerebral blood flow change; the secondary outcomes are N-Back Task accuracy change and the number of participants with treatment-emergent adverse events. The summary also names correlations with cognitive performance and skin pigmentation as aims. A registry outcome definition is not itself an analysis result. The record lists zero analyses, and results for the continuous endpoint and cognitive outcome are not reported in the registry record. It also does not report a statistical plan, model specification, handling of missing observations, or adjustment for multiple testing.

When a study examines several outcomes or associations, multiplicity can be relevant because considering many statistical tests can increase the chance of at least one apparently unusual result. In general, a prespecified hierarchy, adjustment method, or clearly exploratory interpretation can help readers understand that issue. None of those methods is reported in the registry record. No particular multiplicity approach should be attributed to this study.

Over-dispersion is a general concern for some count outcomes when their variability exceeds what a simple probability model expects. It is not a reported feature of this study’s outcomes, and the registry does not specify a count model. The primary endpoint is continuous, and the record’s adverse-event information is presented as participant counts. No model-based estimates or uncertainty measures for these counts are reported. Consequently, elaborate modeling assumptions cannot be evaluated from the registry record.

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("Transcranial Light Therapy")
n   <- c(10)
m   <- c(2.15)
sp  <- c(1.76)
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  Transcranial Light Therapy  10  2.150  1.760  0.891  3.409

11. Multiplicity, Missing Data and Analysis Populations

The registry identifies a primary outcome, change in cerebral blood flow from baseline to Week 5, and two secondary outcomes: change in N-Back Task accuracy from baseline to Week 5 and the number of participants with treatment-emergent adverse events. The study summary also describes intended correlations between cerebral blood flow change and cognitive performance, and between cerebral blood flow change and skin pigmentation. These additional aims are not accompanied by reported analysis details in the registry record.

When a study evaluates multiple outcomes or associations, multiplicity is a general statistical concern: repeated testing can make at least one result appear notable by chance more often than a single prespecified test would. Researchers may address this by prespecifying a hierarchy, adjusting inference, or treating some analyses as exploratory. The registry record does not report whether any such approach was planned or used. It does not report a statistical analysis plan, specific tests, model covariates, or a strategy for interpreting the several stated aims. No multiplicity correction should be assumed.

Missing-data methods and analysis populations are also not reported in the registry record. The record gives enrollment of 10, but does not state how many participants contributed data to the primary endpoint, whether all scheduled measurements were obtained, how missing observations were handled, or which analysis population was used. It does not describe exclusion criteria for analysis or a method for imputing missing values. Without those details, the relationship between enrollment and the analyzed outcome population cannot be assessed.

The registry lists zero analyses. The primary outcome result and N-Back Task accuracy result are not reported in the registry record. Accordingly, readers cannot assess whether the planned outcomes were analyzed as registered, whether secondary aims were exploratory, or how missing data and multiple comparisons affected the reported findings.

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.

Most frequent non-serious adverse event terms

The safety figures are listed for Transcranial Light Therapy Recipients. The registry reports 0 participants affected by serious adverse events among 10 at risk, and 0 deaths. It also reports 3 participants affected by other adverse events among 10 at risk. No serious adverse-event terms are listed. The registry does not identify the terms for the other adverse events in the information.

These counts should be read as descriptive observations for the listed recipients, not as rates calculated against a separate control group. The study is registered as a single-group study, and no randomized comparison arm is listed. The counts therefore do not show whether adverse events were more or less common than they would have been without TLT. They also do not establish whether an event was caused by treatment.

In general, safety interpretation depends on the event definitions, collection and follow-up procedures, exposure, and completeness of reporting. The registry record does not provide event timing, severity details for the other adverse events, or a detailed accounting of safety surveillance. The reported absence of serious events in these counts does not establish that serious risks are absent. Likewise, the other-adverse-event count does not indicate the event types or their clinical significance. The record supports only the stated counts and the limits of their interpretation.

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

The registry record establishes that a completed single-group study enrolled 10 healthy subjects and scheduled continuous, pulsed, and sham transcranial light therapy periods. It identifies change in cerebral blood flow from baseline to Week 5, measured with Diffuse Correlation Spectroscopy, as the primary endpoint. These registry entries describe the study question and structure; they do not report the primary outcome.

The central result needed to assess the stated cerebral blood flow question is not reported in the registry record. There is no numerical estimate of change, no measure of its variability, and no uncertainty interval or inferential test. The record therefore does not show the direction, magnitude, or precision of a cerebral blood flow change. A completed study status does not fill that results gap.

The design also places limits on conclusions. All subjects were scheduled to receive each of the continuous, pulsed, and sham periods, but the record does not report the order or method of comparison. No separate randomized control group is listed. As a result, the record does not establish a treatment-versus-control effect or permit an assessment of causal attribution from the registered information alone.

The registry describes intended associations with cognitive performance and skin pigmentation, and lists N-Back Task accuracy as a secondary outcome. Results for those outcomes or associations are not reported in the registry record. The safety counts indicate 0 participants affected by serious adverse events and 3 affected by other adverse events, among 10 recipients at risk; these observations are descriptive and do not establish causation or comparative safety.

In short, the record communicates what the study intended to measure and provides limited adverse-event counts, but it does not provide the outcome results needed to judge the primary question. It should not be interpreted as evidence that cerebral blood flow changed or did not change, nor as evidence of benefit, lack of benefit, or a specific safety profile.

14. Why This Trial Matters Statistically

This study is statistically informative as an example of the difference between a registered research question and a reported result. The record defines a primary endpoint, its measurement method, unit, summary parameter, and timeframe. Yet a well-defined endpoint cannot answer the question without an estimate and an account of its uncertainty. Because the cerebral blood flow result is not reported in the registry record, readers cannot evaluate the magnitude or precision of the outcome that motivated the study.

The structure also illustrates why a treatment schedule should not be mistaken for a randomized comparison. All subjects were scheduled for continuous, pulsed, and sham TLT, but no separate randomized arms are listed. To interpret comparisons across such periods, readers would need information about order, timing, repeated-measure methods, and the intended contrast. The registry record does not report these details. Statistical conclusions depend on design details as well as on the names of treatments and outcomes.

Planning assumptions deserve similar care. The record describes a hypothetical planning illustration based on an observed effect and equal allocation between two arms, while the study itself is listed as single group. Such illustrations can help explain how assumed effects relate to planning under specified methods, but they are not observed power and do not substitute for the trial’s own design rationale or outcome analysis. The trial’s own sample-size justification is not reported in the registry record.

Finally, the listed adverse-event counts show why safety reporting needs context. Counts without event terms, timing, comparative data, or detailed surveillance information can be reported accurately while still leaving important interpretive questions unresolved. Taken together, these features make this record useful for understanding the importance of transparent results and methods, while limiting conclusions that can be drawn from the information registered.

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 for interpretation is that the registry record does not report a result for the primary cerebral blood flow endpoint. It gives no estimate of baseline-to-Week-5 change, standard deviation, confidence interval, or test result. The primary question therefore cannot be evaluated from the registered results. The record’s completed status does not indicate whether all planned measurements were obtained or analyzed.

The design information is limited for assessing treatment-period comparisons. The study is listed as single group, with all subjects scheduled to receive continuous TLT, pulsed TLT, and sham TLT. The period order, whether assignment of periods was randomized, any washout, the handling of repeated observations, and the planned contrast are not reported in the registry record. A separate randomized comparison group is not listed. These gaps prevent a clear assessment of the comparison strategy and its assumptions.

The registry record does not report participant characteristics beyond describing the subjects as healthy, or detailed eligibility criteria, baseline measurement summaries, adherence, or analysis populations. It does not state how missing observations were handled. Thus, the extent to which outcome findings, if available elsewhere, would represent all enrolled subjects cannot be assessed from the registered information.

The summary describes correlations with cognitive performance and skin pigmentation, but reports no estimates for those aims. The secondary N-Back Task outcome is also without a reported result. The statistical analysis plan, multiplicity approach, and specific methods are not reported. These omissions make it impossible to assess prespecification and the handling of multiple outcomes.

Safety information is limited to aggregate counts. Event terms for other adverse events, timing, and detailed severity or follow-up information are not reported in the registry record. The absence of a separate comparison group further limits comparative safety interpretation. These are limitations of the available registry information and should not be read as proof that unreported methods or results did not exist.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Transcranial Near-Infrared Light in Healthy Subjects: a Cerebral Blood Flow Study With Diffuse Correlation Spectroscopy — NCT03740152.
• Registry record last updated 2020-11-19; status last verified 2020-10.
• Results first posted 2020-11-19.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

NCT03740152 is a completed, single-group device study sponsored by Massachusetts General Hospital. It enrolled 10 healthy subjects and examined Transcranial Light Therapy, with 1 week of continuous TLT, 1 week of pulsed TLT, and 1 week of sham TLT scheduled for all subjects. The primary outcome is change in cerebral blood flow from baseline to Week 5, measured by Diffuse Correlation Spectroscopy and expressed in mm2/s. The registry lists change in N-Back Task accuracy and participants with treatment-emergent adverse events as secondary outcomes.

The record does not report the primary outcome result, cognitive outcome result, analysis methods, missing-data approach, or analysis populations. It reports 0 participants affected by serious adverse events, 3 affected by other adverse events, and 0 deaths among the listed recipients, with 10 at risk for each adverse-event category. These counts are descriptive and do not provide a randomized safety comparison.