Feasibility of Light Therapy for Fatigue N-of-1 Trials: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Feasibility of Light Therapy for Fatigue N-of-1 Trials (NCT04707846), a randomized na study. The primary outcome is Mean System Usability Score (SUS)..

2. Clinical Question

The registry describes a feasibility study intended to assess whether technology could support remote N-of-1 interventions for people experiencing fatigue. Its stated interest includes the feasibility and effectiveness of using the platform to facilitate those personalized trials. However, the primary endpoint recorded is the mean System Usability Score, and no numerical primary result is reported in the registry record.

Fatigue was also assessed as a secondary outcome, alongside pain, concentration, confidence, mood, and participant satisfaction with trial components. These outcomes can address questions about participants’ experiences during different conditions, but their numerical results are not reported in the registry record. The record states that the study’s two groups represent different treatment orders used to counterbalance presentation, not separate intervention groups for between-group outcome comparisons.

3. Trial Design

The study is registered as randomized, unmasked, and crossover. Its title identifies it as a feasibility study of light therapy for fatigue using N-of-1 trials. The registry lists an enrollment of 60 and the status as completed. The study began on 2021-01-20, with primary completion on 2022-01-31.

The brief description outlines a baseline period lasting 2 weeks, during which initial fatigue and other outcomes were assessed. Participants then spent 12 weeks alternating between bright light therapy, dim light therapy, and usual care. They answered daily questions and wore an activity tracker. After 14 weeks, participants could share their opinions about the personalized-trials platform. The registry does not report how many participants completed each part of the study.

The record describes two groups with different treatment orders. The purpose stated for those orders is to counterbalance when bright light, dim light, and usual care are presented. The registry explicitly says that primary and secondary outcomes are not compared between those groups because they are treatment orders rather than distinct interventions. The specific sequence assigned to each group is not reported in the registry record.

The bright and dim conditions used commercial AYO light therapy devices. During usual care periods, participants were instructed to abstain from using those devices and to treat fatigue as they normally would. The record does not provide complete operational details for every treatment period, including a full account of the bright-light instructions.

The registry does not report masking, because the study is listed as having no masking. It does not give the allocation procedure beyond identifying allocation as randomized, nor does it report details of sequence generation or concealment. The study is listed as phase NA, which is a registry classification, not an efficacy finding.

4. Participant Flow and Accounting

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

Overall Study

Analysis population for the primary outcome, as defined in the registry: Though the study utilizes two groups with two treatment orders, this is done to counter-balance the presentation of treatments (bright light, dim light, and usual care). No comparisons of primary or secondary outcomes are conducted between the groups because they are not different interventions, just different orders of the same personalized N-of-1 trial. Interpretation of the study's results are made at the level of the whole sample or the individual participant, not by treatment order.

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: Participants offered primary outcome

6. Primary Endpoint

The registry lists the primary outcome as Mean System Usability Score (SUS)., measured over Assessed once after the results report has been sent to the participant, within 4 months of intervention completion..

The primary endpoint is the mean System Usability Score, or SUS. It is intended to describe participants’ assessment of the Personalized Trials system’s ease of use, complexity, and consistency across the process from recruitment to receiving a results report. The registry describes a validated 10-item questionnaire. Each item uses a Likert rating from Strongly Disagree at 1 to Strongly Agree at 5; individual responses are combined into a composite score out of 100. Higher scores are described as corresponding to greater usability.

The endpoint is recorded as a mean with standard deviation. A mean gives a measure of the central level of reported usability across participants, while the standard deviation describes the spread of scores around that mean. In general, these summaries help distinguish the overall average experience from the degree to which participant experiences vary.

This outcome fits the study’s feasibility focus because the platform itself is part of what the investigators sought to assess. A system that is difficult to use could impede remote data collection and delivery of personalized trial reports, even if the clinical outcomes were measured as planned. The SUS therefore addresses usability rather than fatigue change, effectiveness of a light condition, or comparative treatment benefit.

The questionnaire was to be assessed once after the results report was sent, within 4 months of intervention completion. The numerical mean and standard deviation are not reported in the registry record. Therefore, the endpoint definition explains what was intended to be measured, but does not establish what participants’ ratings were.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a randomized crossover study with an N-of-1 focus. The primary endpoint is a continuous score summarized by a mean and standard deviation. No numerical outcome analysis is reported in the registry record, so the design and endpoint definitions can be described, but estimates of treatment effects or usability cannot be evaluated.

What does crossover mean in this study?

In general, a crossover design exposes participants to more than one condition in a planned sequence, allowing observations from different periods to be related within the same participant. The record describes alternating periods of bright light, dim light, and usual care. It also describes two treatment orders intended to counterbalance when the conditions are presented. The registry does not report the full sequences or the statistical model planned for repeated measurements.

In general, within-person comparisons can account for stable characteristics that differ between people, because each participant contributes observations under multiple conditions. They still require attention to time trends, missing observations, adherence, and possible carryover from one period to another. Carryover means that an earlier condition could influence measurements in a later period. This is a general design consideration; whether and how it was assessed in this study is not reported in the registry record.

What does the primary endpoint summarize?

The SUS combines responses to 10 questionnaire items into a composite score out of 100. The registry states that item ratings range from 1 to 5, from Strongly Disagree to Strongly Agree. The primary summary is a mean and standard deviation. In general, a mean describes the average score, while a standard deviation describes how dispersed scores are around that average. The standard deviation is not the same as the uncertainty in the mean; a confidence interval would be one way to express uncertainty in an estimated mean, but one is not reported.

The planned assessment time is once after the participant has received a results report, within 4 months of intervention completion. The timing ties the usability assessment to the overall platform experience. The registry does not report the number of completed questionnaires, the observed score distribution, or the mean and standard deviation.

How should treatment comparisons be understood?

The registry says the two groups represent treatment orders and that there are no comparisons of primary or secondary outcomes between them. This means the groups should not be interpreted as separate treatment arms for estimating bright-light versus dim-light effects. The stated conditions are presented within the crossover approach. The registry lists secondary outcomes that include daily and weekly fatigue measures and ecological momentary assessments of fatigue, pain, concentration, confidence, and mood. It does not report the model or contrast used to compare measurements across conditions.

In general, repeated observations from the same participant are correlated rather than independent. Analyses of crossover or repeated-measures data usually need to reflect that dependence; treating every daily observation as independent can lead to incorrect uncertainty estimates. This is a general statistical principle, not a description of an analysis documented for this study. The statistical model, handling of serial dependence, and approach to within-person estimates are not reported in the registry record.

What do randomization and no masking tell readers?

Randomization indicates that assignment to the treatment orders was described as random. In general, random assignment can reduce systematic differences in allocation, but the record does not specify the sequence-generation procedure or allocation concealment. The study is listed as having no masking. Participants would therefore not be described as masked in the registry, and the record does not report masked outcome assessment. For a self-reported usability endpoint, responses capture participants’ reported experience; they are not an objective measure of treatment effect.

The registry does not report a statistical analysis plan, interim analyses, or a sample-size justification. Enrollment is listed as 60, but that number alone does not establish the precision of the primary endpoint or the ability to detect a treatment-period difference. No calculations of observed power or effect estimates are reported. General statistical practice favors interpreting estimates and their uncertainty rather than treating a sample size or a single significance test as a complete account of evidence.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 18 outcome measures, including the primary usability endpoint and secondary measures related to fatigue, participant satisfaction, pain, concentration, confidence, and mood. Considering multiple outcomes can raise the chance of apparently notable findings arising by chance when many statistical tests are performed. In general, analysts may prespecify a primary outcome, adjust for multiple comparisons, or distinguish confirmatory from exploratory analyses. The registry record does not report a multiplicity strategy or explain how secondary outcomes were to be interpreted together.

The record lists zero analyses. It does not report outcome-specific estimates, hypothesis tests, confidence intervals, or a statistical analysis plan. Accordingly, it is not possible to determine whether any multiplicity adjustment was used, whether outcomes were analyzed as planned, or whether findings were selected for reporting.

Missing data are particularly relevant in remote studies with daily questions and activity tracking, because repeated measurements may not all be available for every participant. In general, the amount and pattern of missingness can affect both the estimate and its precision; methods that assume data are missing at random rely on assumptions that should be described and assessed. The registry record does not report completeness of daily responses, missing-data patterns, imputation, or other missing-data methods.

The record does not define analysis populations, such as whether summaries include all enrolled participants, only participants completing a particular period, or another group. It also does not report participant flow through the study or how many provided the primary SUS assessment. These omissions prevent assessment of whether the reported enrollment corresponds to the outcome-analysis population. No inference about attrition or the handling of incomplete participation can be made from the registry record.

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 5% reporting threshold.

The registry lists serious adverse events for Group 1 as 0 affected among 28 at risk and for Group 2 as 0 affected among 32 at risk. It also lists other adverse events as 0 affected among 28 at risk in Group 1 and 0 affected among 32 at risk in Group 2. Deaths are listed as 0 in each group, and no serious adverse event terms are listed.

These are reported event counts within the registry’s group entries. A count of zero means that no affected participants are recorded for that category in the entry; it does not establish that no symptoms or events occurred, nor that every possible event was detected. The record does not report details about event definitions, collection methods, exposure time, or completeness of safety reporting.

The groups represent different treatment orders, not separate intervention groups for the study’s primary and secondary outcome comparisons. The adverse-event entries should therefore be read as registry safety summaries for those listed groups, not as a randomized comparison establishing relative safety between bright light, dim light, and usual care. The counts alone do not demonstrate that any condition is risk-free.

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

This study addresses a practical question about conducting personalized trials remotely: whether participants can use a platform that supports a baseline period, alternating conditions, daily reporting, activity tracking, and delivery of an individual results report. The primary endpoint focuses on usability of that system. The study also planned to assess fatigue and several other participant-reported outcomes.

The registry record identifies the study as completed and lists an enrollment of 60. Those details describe the study’s administrative status and recorded enrollment, not the outcome of the usability assessment. The mean SUS, its standard deviation, and numerical findings for the secondary outcomes are not reported in the registry record. As a result, readers cannot determine from this record how usable participants found the platform or what the fatigue measurements showed.

Even if a usability score were available, it would answer a different question from whether light therapy changes fatigue. A favorable usability score would indicate reported ease or experience with the system, not clinical effectiveness. Likewise, any within-person fatigue pattern would need an appropriate analysis and uncertainty information before its magnitude and reliability could be assessed. The registry does not provide those estimates or analysis details.

The randomized treatment orders were intended to counterbalance presentation, and the record says the groups were not used for comparisons of primary or secondary outcomes. Their group labels should not be treated as comparisons of distinct interventions. The record also does not provide enough information to assess adherence, period effects, carryover, missing responses, or variation in individual treatment responses.

The safety entries report zero affected participants in the listed adverse-event categories for both groups. These counts are limited to what the registry records and do not establish absence of risk. Overall, the record describes the design and measurement goals, but it does not report the numerical results needed to judge usability, fatigue outcomes, or the precision of any estimated differences.

13. Why This Trial Matters Statistically

N-of-1 approaches place emphasis on measurements within individuals over time rather than relying solely on averages across separate groups. That makes the quality and completeness of repeated measurements important. This study’s remote format combined daily questions and an activity tracker with alternating light and usual-care periods, while also asking participants to assess the platform itself. It therefore illustrates how a feasibility question can involve both the intervention sequence and the tools used to collect and return information.

The distinction between platform usability and clinical outcomes is statistically important. A usability endpoint can assess whether participants found the system workable, but it cannot substitute for outcome comparisons. Likewise, a treatment-period estimate does not by itself measure whether the platform was acceptable or feasible. Keeping these questions separate helps avoid interpreting one type of result as evidence for another.

The crossover structure also highlights the value of accounting for repeated observations from the same participant. In general, within-person data contain dependence over time, and conclusions can be sensitive to period effects, missing measurements, or lingering effects from earlier conditions. Clear reporting of the planned analysis and the resulting estimates would allow readers to assess how those features were handled.

The registry lists multiple outcomes but does not report analyses or numerical results. This makes transparent outcome reporting especially relevant: readers need to know which outcomes were measured, how incomplete data were treated, and how estimates relate to uncertainty. Without those details, the design can be understood, but the evidence about platform usability and fatigue cannot be evaluated statistically.

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 important details are not reported in the registry record. The numerical primary SUS result and its standard deviation are absent, as are numerical results for the secondary outcomes. The record lists zero analyses, so it does not provide estimates, confidence intervals, or inferential tests through which the precision of outcome findings could be assessed.

The registry does not give the complete treatment sequences, the statistical model, or the method for deriving within-person comparisons. It does not report whether period effects or carryover were assessed. Those issues are relevant in general to crossover studies, but the available record does not show how they were addressed in this study.

Participant flow and outcome completeness are also not reported. The number of participants who completed the intervention periods or posted the post-report SUS assessment is not given. There is no information about missing daily responses, activity-tracker data, adherence, or the handling of incomplete observations. The analysis populations are not defined.

The record does not report a multiplicity approach for the listed outcomes, a statistical analysis plan, interim analyses, or a sample-size justification. It also does not provide detailed eligibility characteristics, allocation procedures beyond randomization, or masking of outcome assessment. These limitations restrict interpretation of the methods and prevent a statistical assessment of the results, independent of the study’s completed status.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Feasibility of Light Therapy for Fatigue N-of-1 Trials — NCT04707846.
• Registry record last updated 2023-02-08; status last verified 2023-01.
• Results first posted 2023-02-08.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

The registry describes a completed randomized, unmasked crossover feasibility study of a remote personalized-trials platform for self-identified fatigue. The listed enrollment is 60. Participants had a 2-week baseline and then spent 12 weeks alternating between bright light therapy, dim light therapy, and usual care, with daily questions and activity tracking. The primary endpoint was mean System Usability Score, assessed once after the results report was sent and within 4 months of intervention completion.

The two groups represented different treatment orders intended to counterbalance presentation; the registry says outcomes were not compared between those groups. The record lists 18 outcome measures and zero analyses. Numerical primary and secondary outcome results are not reported in the registry record. Safety entries list zero serious adverse events, zero other adverse events, and zero deaths in each group. The record does not report analysis methods, missing-data handling, participant flow, or the numerical usability result.